ICES Journal of Marine Science - recent issues

Using a double codend to reduce discard mortality

Broadhurst, M. K., Millar, R. B., Uhlmann, S. S. — Wed, 04 Nov 2009 08:22:29 PST

Broadhurst, M. K., Millar, R. B., and Uhlmann, S. S. 2009. Using a double codend to reduce discard mortality. – ICES Journal of Marine Science, 66: 2077–2081.

Traditional technical strategies for mitigating collateral fishing mortality have involved improving gear selectivity (to reduce bycatch) and, more recently, concomitant changes to onboard handling procedures to reduce some of the negative impacts to the remaining discards. A less common approach is to modify gears physically to minimize deleterious catching mechanisms and subsequent mortalities during fishing. This study aimed to investigate the utility of the latter category of modifications for penaeid trawls by separating a codend into two compartments (termed a double codend) to alleviate interactions between catches. Compared with a conventional design, the double codend significantly reduced the immediate (from 17.1 to 13.8%) and short-term (22.5 to 17.1%) mortalities of discarded juvenile school prawns (Metapenaeus macleayi). The effectiveness of the double codend remained independent of other factors known to affect the fate of discarded juvenile M. macleayi, including cloud cover and, owing to minimal variability, the weight of the total catch. However, irrespective of the codend configuration, overall mortalities were also positively correlated with the quantity of jellyfish. We conclude that when combined with modifications to improve selectivity and appropriate onboard handling strategies, compartmentalizing codend catches could cumulatively reduce unaccounted fishing mortality.

Comment on: Williams et al. (2009) "Australia's deep-water reserve network: implications of false homogeneity for classifying abiotic surrogates of biodiversity". ICES Journal of Marine Science, 66: 214-224

Harris, P. T., Heap, A. D., Anderson, T. J., Brooke, B. — Wed, 04 Nov 2009 08:22:29 PST

Harris, P. T., Heap, A. D., Anderson, T. J., and Brooke, B. 2009. Comment on: Williams et al. (2009) "Australia's deep-water reserve network: implications of false homogeneity for classifying abiotic surrogates of biodiversity". ICES Journal of Marine Science, 66: 214–224. – ICES Journal of Marine Science, 66: 2082–2085.

Williams et al. (2009) report on new multibeam sonar bathymetry and underwater video data collected from submarine canyons and seamounts on Australia's southeast continental margin to "investigate the degree to which geomorphic features act as surrogates for benthic megafaunal biodiversity" (p. 214). The authors describe what they view as deficiencies in the design of the Marine Protected Areas (MPAs) in the southeast region of Australia, in which geomorphology information was employed as a surrogate to infer regional-scale patterns of benthic biodiversity. This comment is designed to support and underscore the importance of evaluating MPA designs and the validity of using abiotic surrogates such as geomorphology to infer biodiversity patterns, and also seeks to clarify some of the discrepancies in geomorphic terminologies and approaches used between the original study and the Williams et al. (2009) evaluation. It is our opinion that the MPA design criteria used by the Australian Government are incorrectly reported by Williams et al. (2009). In particular, we emphasize the necessity for consistent terminology and approaches when undertaking comparative analyses of geomorphic features. We show that the MPA selection criteria used by the Australian Government addressed the issues of false homogeneity described by Williams et al. (2009), but that final placement of MPAs was based on additional stakeholder considerations. Finally, we argue that although the Williams et al. (2009) study provides valuable information on biological distributions within seamounts and canyons, the hypothesis that geomorphic features (particularly seamounts and submarine canyons) are surrogates for benthic biodiversity is not tested explicitly by their study.

Remarks on "Comment on: Williams et al. (2009) Australia's deep-water reserve network: implications of false homogeneity for classifying abiotic surrogates of biodiversity, ICES Journal of Marine Science, 66: 214-224" by Peter T. Harris, Andrew D. Heap, Tara J. Anderson, and Brendan Brooke

Williams, A., Bax, N. J., Kloser, R. J. — Wed, 04 Nov 2009 08:22:29 PST

Williams, A., Bax, N. J., and Kloser, R. J. 2009. Remarks on "Comment on: Williams et al. (2009) Australia's deep-water reserve network: implications of false homogeneity for classifying abiotic surrogates of biodiversity, ICES Journal of Marine Science, 66: 214–224" by Peter T. Harris, Andrew D. Heap, Tara J. Anderson, and Brendan Brooke. – ICES Journal of Marine Science, 66: 2086–2088.

Commitment by many nations at the 2002 World Summit on Sustainable Development to complete national networks of Marine Protected Areas (MPAs) by 2012 focused attention on MPA design and implementation, especially for the deep waters that make up the majority of many national EZs. Further, there is a focus on conservation in the High Seas through the Convention on Biological Biodiversity and the FAO, e.g. for seamounts and other vulnerable benthic habitats. Any manuscript that raises basic issues on one identified area for conservation is therefore a prospectively useful addition to the international debate. The Comment by Harris et al. (2009) on a paper authored by myself and colleagues (Williams et al., 2009) is a potentially useful contribution. The authors provide data, examples, and insights into aspects of the design and planning process for Australia's SE network of reserves. Here, we address the main question of how geological descriptions can be used or modified to provide the most information on marine biodiversity patterns for use in conservation planning—in the context of the major points raised by Harris et al. (2009).

A retrospective analysis to explore the applicability of fish biomarkers and sediment bioassays along contaminated salinity transects

Wed, 04 Nov 2009 08:22:29 PST

Schipper, C. A., Lahr, J., van den Brink, P. J., George, S. G., Hansen, P-D., da Silva de Assis, H. C., van der Oost, R., Thain, J. E., Livingstone, D., Mitchelmore, C., van Schooten, F-J., Ariese, F., Murk, A. J., Grinwis, G. C. M., Klamer, H., Kater, B. J., Postma, J. F., van der Werf, B., and Vethaak, A. D. 2009. A retrospective analysis to explore the applicability of fish biomarkers and sediment bioassays along contaminated salinity transects. – ICES Journal of Marine Science, 66: 2089–2105.

Biological-effects monitoring in estuarine environments is complex as a result of strong gradients and fluctuations in salinity and other environmental conditions, which may influence contaminant bioavailability and the physiology and metabolism of the organisms. To select the most robust and reliable biological-effect methods for monitoring and assessment programmes, a large-scale field study was conducted in two estuarine transects in the Netherlands. The locations ranged from heavily polluted harbour areas (the ports of Rotterdam and Amsterdam) to cleaner coastal and freshwater sites. Assessment methods used included a variety of biomarkers in flounder (Platichthys flesus) and a range of in vitro (sediment extracts) and in vivo bioassays. Multivariate statistical analysis was applied to investigate correlations and relationships between various biological effects and contaminant levels in flounder liver or sediments. Several biological methods seemed to be too much affected by salinity differences for routine use in estuaries. The most discriminative biomarkers in the study were hepatic metallothionein content and biliary 1-OH pyrene in fish. Mechanism-based in vitro assays DR-CALUX and ER-CALUX applied to sediment extracts for screening of potential toxicity were much more responsive than in vivo bioassays with macro-invertebrates using survival as an endpoint.

Spatial predictive distribution modelling of the kelp species Laminaria hyperborea

Bekkby, T., Rinde, E., Erikstad, L., Bakkestuen, V. — Wed, 04 Nov 2009 08:22:29 PST

Bekkby, T., Rinde, E., Erikstad, L., and Bakkestuen, V. 2009. Spatial predictive distribution modelling of the kelp species Laminaria hyperborea. – ICES Journal of Marine Science, 66: 2106–2115.

The kelp species Laminaria hyperborea constitutes highly productive kelp forest systems hosting a broad diversity of species and providing the basis for commercial kelp harvesting and, through its productivity, the fishing industry. Spatial planning and management of this important habitat and resource needs to be based on distribution maps and detailed knowledge of the main factors influencing the distribution. However, in countries with a long and complex coastline, such as Norway, detailed mapping is practically and economically difficult. Consequently, alternative methods are required. Based on modelled and field-measured geophysical variables and presence/absence data of L. hyperborea, a spatial predictive probability model for kelp distribution is developed. The influence of depth, slope, terrain curvature, light exposure, wave exposure, and current speed on the distribution of L. hyperborea are modelled using a generalized additive model. Using the Akaike Information Criterion, we found that the most important geophysical factors explaining the distribution of kelp were depth, terrain curvature, and wave and light exposure. The resulting predictive model was very reliable, showing good ability to predict the presence and absence of kelp.

The fishery for whiteweed, Sertularia cupressina (Cnidaria, Hydrozoa), in the Wadden Sea, Germany: history and anthropogenic effects

Wagler, H., Berghahn, R., Vorberg, R. — Wed, 04 Nov 2009 08:22:29 PST

Wagler, H., Berghahn, R., and Vorberg, R. 2009. The fishery for whiteweed, Sertularia cupressina (Cnidaria, Hydrozoa), in the Wadden Sea, Germany: history and anthropogenic effects. – ICES Journal of Marine Science, 66: 2116–2120.

The whiteweed fishery in the German Wadden Sea did not close as a consequence of the loss of whiteweed beds, but rather because of declining markets. To this day, neither the assumed disappearance of whiteweed beds nor the assumed decrease in whiteweed abundance has been substantiated. Even if such a decrease were to be demonstrated, the causes for the decline would more likely have been eutrophication and anthropogenic changes in the hydrodynamics of the Wadden Sea than the activities of the shrimp and mussel fisheries or the former whiteweed fishery.

Can we infer dredge fishing effort from macrobenthic community structure?

Wed, 04 Nov 2009 08:22:29 PST

Gaspar, M. B., Carvalho, S., Constantino, R., Tata-Regala, J., Cúrdia, J., and Monteiro, C. C. 2009. Can we infer dredge fishing effort from macrobenthic community structure? – ICES Journal of Marine Science, 66: 2121–2132.

The effects of commercial fishing effort (FE) on macrobenthic community structure were analysed in geographically related fishing grounds separated into three groups: non-exploited (NE), moderately exploited (ME), and highly exploited (HE). Number of species, abundance, Margalef species richness, and Shannon–Wiener diversity were significantly higher in NE than in exploited areas. The first two were also significantly higher in HE than in ME areas. Measures of taxonomic diversity differed depending on whether annelids, molluscs, and crustaceans were combined or analysed separately. Crustaceans seemed to be the most vulnerable to bivalve dredging because significantly lower values were observed for them in the HE areas than in the ME and NE areas for this group. Although the samples were taken at the end of the closed season, macrobenthic communities still showed differences that may be related to FE, especially in trophic structure. Carnivory was particularly dominant in HE areas. The ratio of carnivory to filter-feeding was significantly correlated with FE, with higher values being observed in HE areas and lower values in NE areas.

Average seasonal changes in chlorophyll a in Icelandic waters

Guthmundsson, K., Heath, M. R., Clarke, E. D. — Wed, 04 Nov 2009 08:22:29 PST

Guðmundsson, K., Heath, M. R., and Clarke, E. D. 2009. Average seasonal changes in chlorophyll a in Icelandic waters. – ICES Journal of Marine Science, 66: 2133–2140.

The standard algorithms used to derive sea surface chlorophyll a concentration from remotely sensed ocean colour data are based almost entirely on the measurements of surface water samples collected in open sea (case 1) waters which cover ~60% of the worlds oceans, where strong correlations between reflectance and chlorophyll concentration have been found. However, satellite chlorophyll data for waters outside the defined case 1 areas, but derived using standard calibrations, are frequently used without reference to local in situ measurements and despite well-known factors likely to lead to inaccuracy. In Icelandic waters, multiannual averages of 8-d composites of SeaWiFS chlorophyll concentration accounted for just 20% of the variance in a multiannual dataset of in situ chlorophyll a measurements. Nevertheless, applying penalized regression spline methodology to model the spatial and temporal patterns of in situ measurements, using satellite chlorophyll as one of the predictor variables, improved the correlation considerably. Day number, representing seasonal variation, accounted for substantial deviation between SeaWiFS and in situ estimates of surface chlorophyll. The final model, using bottom depth and bearing to the sampling location as well as the two variables mentioned above, explained 49% of the variance in the fitting dataset.

Dichelesthium oblongum (Copepoda: Dichelesthiidae) infestation in wild-caught Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus

Fast, M. D., Sokolowski, M. S., Dunton, K. J., Bowser, P. R. — Wed, 04 Nov 2009 08:22:29 PST

Fast, M. D., Sokolowski, M. S., Dunton, K. J., and Bowser, P. R. 2009. Dichelesthium oblongum (Copepoda: Dichelesthiidae) infestation in wild-caught Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus. – ICES Journal of Marine Science, 66: 2141–2147.

Atlantic sturgeon were sampled in autumn 2007 and 2008 along the New York Bight. The fish were examined for the presence of external parasites, and blood, fin, and opercula biopsies were collected for subsequent serum analysis and histopathological evaluation. Dichelesthium oblongum, a parasitic copepod, was observed on 93% of the sturgeon sampled (77 out of 83) between Rockaway and Jones Beaches, NY, and Sandy Hook, NJ. During the course of the examinations, grossly visible lesions associated with the attachment and feeding of juvenile stages of D. oblongum were noted on the operculum, pectoral, dorsal, and anal fins of infested fish. Significant differences were observed between the level of infestation and serum chemistry across sampling sites, such that the most heavily infested fish were caught off Jones Beach (15.8 ± 2.79 lice fish^–1), higher infestations than at Rockaway Beach (8.86 ± 0.89 lice fish^–1) and Sandy Hook (5.31 ± 1.40 lice fish^–1). Animals from Jones Beach also indicated ion loading (i.e. sodium, calcium, and magnesium), possibly as a result of stress or water loss through D. oblongum infestation compromising the epithelial barrier. The interaction of the environment and parasite with host life-history characteristics are discussed in terms of their ecological significance to this threatened fish species.

The risk to fishery performance associated with spatially resolved management of Antarctic krill (Euphausia superba) harvesting

Hill, S. L., Trathan, P. N., Agnew, D. J. — Wed, 04 Nov 2009 08:22:29 PST

Hill, S. L., Trathan, P. N., and Agnew, D. J. 2009. The risk to fishery performance associated with spatially resolved management of Antarctic krill (Euphausia superba) harvesting. – ICES Journal of Marine Science, 66: 2148–2154.

The ecosystem approach to fisheries attempts to define objectives for target species, the wider ecosystem, and critically, the fishery itself. Proposals for implementing the approach often include spatial restrictions on harvesting, so it is important to understand how these will affect fishery performance. One metric of potential performance is the probability of encountering exploitable densities of a target species at the scale of fishing operations. The probability of encountering exploitable densities of Antarctic krill, Euphausia superba, at the scale of 1 nautical mile during an acoustic survey was predicted by bathymetry and the mean krill density at the larger scale at which the fishery is managed. This suggests that the risk to fishery performance will increase if management actions relocate the fishery into deeper water. The results also suggest that ecosystem models resolved to the spatial scale of management units could usefully predict effects at the scale of fishing operations. However, correct parameterization of these models will require better characterization of threshold densities for efficient exploitation. Finally, the distribution of catch and fishing effort over an entire fishing season reflected the distribution of krill density observed during the survey.

Dispersal and settlement of sea scallop larvae spawned in the fishery closed areas on Georges Bank

Wed, 04 Nov 2009 08:22:29 PST

Tian, R. C., Chen, C., Stokesbury, K. D. E., Rothschild, B. J., Cowles, G. W., Xu, Q., Hu, S., Harris, B. P., and Marino II, M. C. 2009. Dispersal and settlement of sea scallop larvae spawned in the fishery closed areas on Georges Bank. – ICES Journal of Marine Science, 66: 2155–2164.

Three fishery closed areas in the Georges Bank (GB) region were implemented in 1994 to protect depleted groundfish stocks for population replenishment. However, the drift and ultimate destination of larvae spawned in the closed areas have not been analysed specifically within the framework of ocean currents. To assess the efficiency of the closed areas as population replenishment sources, we conducted a simulation-based analysis on the dispersal and settlement of sea scallop larvae spawned in the closed areas from 1995 to 2005 using circulation fields computed by the Finite-Volume Coastal Ocean Model, scallop survey data, and a population dynamics model. Closed area I located in the Great Southern Channel (GSC) had a persistently high rate of larval retention (86% on average). For closed area II located on eastern GB, a considerable quantity of larvae was dispersed out of the domain. For the Nantucket Lightship Closed Area located on Nantucket Shoals, larvae consistently drifted away from the region during the 11 years simulated. Our simulation revealed three high-retention regions that are the most suitable for closed-area selection and rotational fishery management in terms of larval supply to the GB–GSC region.

Estimating von Bertalanffy growth parameters from growth increment data using a linear mixed-effects model, with an application to the sea scallop Placopecten magellanicus

Hart, D. R., Chute, A. S. — Wed, 04 Nov 2009 08:22:29 PST

Hart, D. R., and Chute, A. S. 2009. Estimating von Bertalanffy growth parameters from growth increment data using a linear mixed-effects model, with an application to the sea scallop Placopecten magellanicus. – ICES Journal of Marine Science, 66: 2165–2175.

We introduce a novel linear mixed-effects method for estimating von Bertalanffy growth parameters from growth increment data that lack explicit age information. The method is simple to implement and can incorporate and estimate variability in both the asymptotic size L and the Brody growth coefficient K. Simulations indicate that estimates from the method are accurate over a range of conditions. The method is applied to growth data from more than 6000 Atlantic sea scallop (Placopecten magellanicus) shells from the Mid-Atlantic Bight and Georges Bank. Sea scallops grow to a larger asymptotic shell height on Georges Bank than on the Mid-Atlantic Bight and in areas closed to fishing on Georges Bank than on the fished portions. Depth and latitude had significant effects on scallop growth in both the Mid-Atlantic and Georges Bank, with smaller asymptotic shell heights in deeper water and at higher latitudes.

Microsatellite variability in European anchovy (Engraulis encrasicolus) calls for further investigation of its genetic structure and biogeography

Zarraonaindia, I., Pardo, M. A., Iriondo, M., Manzano, C., Estonba, A. — Wed, 04 Nov 2009 08:22:29 PST

Zarraonaindia, I., Pardo, M. A., Iriondo, M., Manzano, C., and Estonba, A. 2009. Microsatellite variability in European anchovy (Engraulis encrasicolus) calls for further investigation of its genetic structure and biogeography. – ICES Journal of Marine Science, 66: 2176–2182.

Attention to genetic and ecological perspectives can enhance strategies for using fishery resources sustainably. A potentially important application is the use of molecular markers to assess the genetic stock structure of a harvested species. In this study, seven microsatellite markers were analysed in anchovy samples from the Bay of Biscay, the Gulf of Cádiz, and the Gulf of Lions to assess the genetic structure of anchovy (Engraulis encrasicolus) populations in the Bay of Biscay and to infer the biogeographic origin of these populations. All samples showed a deficit of heterozygotes that could be explained by non-random mating, Wahlund's effect, and especially by the presence of null alleles. Global F_ST and R_ST values, uncorrected and corrected for null alleles, were significant. There was significant genetic heterogeneity between two populations in the Bay of Biscay, suggesting that anchovy there may not be panmictic. Moreover, the results reinforce the hypothesis of a recent common ancestor shared by Bay of Biscay and western Mediterranean anchovy. These results, together with those of earlier studies, suggest merit in further investigating spatio-temporal genetic variation among anchovy populations in the Northeastern Atlantic.

Integrating spatial and temporal mortality from herring on capelin larvae: a study in the Barents Sea

Pedersen, O. P., Pedersen, T., Tande, K. S., Slagstad, D. — Wed, 04 Nov 2009 08:22:29 PST

Pedersen, O. P., Pedersen, T., Tande, K. S., and Slagstad, D. 2009. Integrating spatial and temporal mortality from herring on capelin larvae: a study in the Barents Sea. – ICES Journal of Marine Science, 66: 2183–2194.

Barents Sea herring and capelin are commercially very important fish stocks. We investigate the spatial and temporal mortality rate of capelin larvae in 2001 as a function of herring predation. Our methods are based on Lagrangian modelling, field surveys, and experimental data. The impact of juvenile herring predation on capelin recruitment is corroborated, in particular the importance of the integrated spatio-temporal overlap between the two stocks. Capelin larvae were reduced to 20–50% in two weeks in accordance with different simulation scenarios. Hamre advanced a hypothesis in 1994 that juvenile herring are important predators of capelin larvae and a main cause of poor capelin recruitment in years when herring are very abundant in the Barents Sea. This hypothesis is supported through the results of this work.

A critical review of Pacific salmon marine research relating to climate

Chittenden, C. M., Beamish, R. J., McKinley, R. S. — Wed, 04 Nov 2009 08:22:29 PST

Chittenden, C. M., Beamish, R. J., and McKinley, R. S. 2009. A critical review of Pacific salmon marine research relating to climate. – ICES Journal of Marine Science, 66: 2195–2204.

Several studies in the North Pacific Ocean have documented the consequences of rising sea surface temperatures and the advancement of the spring freshet on ocean productivity. The altering of ocean productivity has also been correlated with changes in the marine survival and geographic occurrence of some Pacific salmon populations. Knowledge of the marine survival and position of salmon in the Pacific Ocean are derived typically from mark-recapture studies. As a result, the migratory behaviour and associated survival estimates of salmon in real time are not known. Major information gaps also exist in terms of stock-specific marine behaviour and survival—especially as they relate to recent changes in climate. Acoustic telemetry and other modern tools enable researchers to answer specific questions about environmental, physiological, and genetic effects on individual salmon survival and behaviour, which had not been possible previously. As climate trends increasingly exceed those found in historical records, there is an urgent need for information that will improve fishery management and conservation decisions. International, multidisciplinary research teams using modern technologies could accomplish this.

Determination of Atlantic bluefin tuna (Thunnus thynnus) spawning time within a transport cage in the western Mediterranean

Gordoa, A., Olivar, M. P., Arevalo, R., Vinas, J., Moli, B., Illas, X. — Wed, 04 Nov 2009 08:22:29 PST

Gordoa, A., Olivar, M. P., Arevalo, R., Viñas, J., Molí, B., and Illas, X. 2009. Determination of Atlantic bluefin tuna (Thunnus thynnus) spawning time within a transport cage in the western Mediterranean. – ICES Journal of Marine Science, 66: 2205–2210.

For the first time, tuna spawning in a transport cage being towed from the western Mediterranean spawning ground to a fattening facility off the coast of northeastern Spain was examined during the 2008 fishing season. Daylight and night surface plankton samples were collected using bongo nets located in front of and behind the transport cage. The results for the different time intervals revealed clear and massive nocturnal spawning from 03:00 to 05:00, when the rear bongo was completely jammed with eggs (up to 250 000–300 000 eggs per 1000 m³). Egg size and morphology were consistent with the features of Thunnus thynnus eggs, and identification was confirmed by genetic analysis. Microscopic examination showed the eggs to be in the very early developmental stages. Spawning took place every night over the entire journey. The study showed that neither captivity nor handling/environmental changes along the route inhibited T. thynnus spawning to a very precise biological clock. The study also revealed the diel temporal concurrence of T. thynnus spawning and jellyfish larvae at the sea surface.

Fuzzy diel patterns in catchability of deep-water species on the continental margin

Bahamon, N., Sarda, F., Aguzzi, J. — Wed, 04 Nov 2009 08:22:30 PST

Bahamon, N., Sardà, F., and Aguzzi, J. 2009. Fuzzy diel patterns in catchability of deep-water species on the continental margin. – ICES Journal of Marine Science, 66: 2211–2218.

Exploited deep-water fish communities on continental margins are poorly understood in terms of variations in species composition and abundance by depth and season as a response to diel changes in light intensity and length of photoperiod. Innovative fuzzy clustering and traditional agglomerative hierarchical clustering methods were applied to data from bottom trawls collected continuously for 4 d in October and June, on the shelf (100–110 m) and upper slope (400–430 m). Fuzzy clustering was more effective than hierarchical clustering at characterizing diel variations in catches from the upper slope because the species assemblage did not show a distinct day and night structure. On the shelf, the species assemblages shifted abruptly between a diurnal and a nocturnal structure at sunset and sunrise, and the two clustering methods yielded similar results. Endobenthic decapods with marked crepuscular-nocturnal emergence from the substratum were mostly responsible for this pattern. No clearly discernible diel pattern was found with the dampening of light intensity with depth, weakening the behavioural response of endobenthos to the day–night cycle. The results indicated that the regulatory effect of the light cycle on diel activity rhythms weakens with depth.

A "seascape genetic" snapshot of Sebastes marinus calls for further investigation across the North Atlantic

Pampoulie, C., Gislason, D., Danielsdottir, A. K. — Wed, 04 Nov 2009 08:22:30 PST

Pampoulie, C., Gíslason, D., and Daníelsdóttir, A. K. 2009. A "seascape genetic" snapshot of Sebastes marinus calls for further investigation across the North Atlantic. – ICES Journal of Marine Science, 66: 2219–2222.

A collection of 376 golden redfish (Sebastes marinus) from several fishing grounds in the North Atlantic in late 2001 was genotyped at nine microsatellite loci to provide preliminary information on the possible genetic structure in this species. Landscape genetic analysis revealed the presence of two distinct genetic pools within the North Atlantic, suggesting that S. marinus might be structured within the North Atlantic and should be the subject of more investigation.

End-to-end foodweb control of fish production on Georges Bank

Collie, J. S., Gifford, D. J., Steele, J. H. — Wed, 04 Nov 2009 08:22:30 PST

Collie, J. S., Gifford, D. J., and Steele, J. H. 2009. End-to-end foodweb control of fish production on Georges Bank. – ICES Journal of Marine Science, 66: 2223–2232.

The ecosystem approach to management requires the productivity of individual fish stocks to be considered in the context of the entire ecosystem. We derive an annual end-to-end budget for the Georges Bank ecosystem, based on data from the GLOBEC programme and fisheries surveys for the years 1993–2002. Scenarios based on this budget describe the consequences of various alterations in the Georges Bank trophic web: reduced nutrient input, increased benthic production, removal of carnivorous plankton, and changes in species dominance within fish guilds. Potential yields of cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) are compared with historical catches and estimates of maximum sustainable yield (MSY) from recent stock assessments. The MSYs of cod and haddock can be met if the fish community is restructured to make them the dominant species in their respective diet-defined guilds. A return to the balance of fish species present in the early 20th century would depend on an increase in the fraction of primary production going to the benthos rather than to plankton. Estimates of energy flux through the Georges Bank trophic web indicate that rebuilding the principal groundfish species to their MSY levels requires restructuring of the fish community and repartitioning of energy within the foodweb.

Temporal variability in southern North Sea epifauna communities after the cold winter of 1995/1996

Neumann, H., Reiss, H., Rakers, S., Ehrich, S., Kroncke, I. — Wed, 04 Nov 2009 08:22:30 PST

Neumann, H., Reiss, H., Rakers, S., Ehrich, S., and Kröncke, I. 2009. Temporal variability in southern North Sea epifauna communities after the cold winter of 1995/1996. – ICES Journal of Marine Science, 66: 2233–2243.

Epifauna communities in the southeastern North Sea were studied from 1998 to 2008 to evaluate the effect of hydroclimatic change in community structure. The spatial analysis revealed four communities along the West and North Frisian coasts, on the Oyster Ground, and on the Dogger Bank. The variability between communities was caused mainly by differing abundance of widespread species such as Asterias rubens, probably reflecting differences in environmental conditions, e.g. temperature variation and food supply. Community structure varied between 1998–2000 and 2003–2008 at the shallow West and North Frisian coasts. The hypothesis is that epibenthic communities in these areas were severely affected by the cold winter of 1995/1996, resulting in the outbreak of the opportunistic brittlestar Ophiura albida and followed by characteristic post-disturbance succession stages from 1998 to 2000. The period between 2003 and 2008 was characterized by a continuous decrease in O. albida and by an increase in other species and diversity in the coastal areas. In contrast, secondary production increased in all four areas after 2003, probably because of an increase in sea surface temperature (SST) and in the length of the warming season. We conclude that the cold winter affected epifauna mainly in shallow areas and that the increasing SST influenced the epifauna in the entire southeastern North Sea mainly through an increased food supply.

The importance of lipid-rich fish prey for Cape gannet chick growth: are fishery discards an alternative?

Mullers, R. H. E., Navarro, R. A., Crawford, R. J. M., Underhill, L. G. — Wed, 04 Nov 2009 08:22:30 PST

Mullers, R. H. E., Navarro, R. A., Crawford, R. J. M., and Underhill, L. G. 2009. The importance of lipid-rich fish prey for Cape gannet chick growth: are fishery discards an alternative? – ICES Journal of Marine Science, 66: 2244–2252.

A recent decline in population numbers of Cape gannets (Morus capensis) breeding off the west coast of South Africa coincided with decreased availability of lipid-rich fish prey: anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax). Seabirds can use fishery discards as an alternative, but the quality of this food in the Benguela ecosystem is lower than that of their natural prey species. We consider whether chick growth and survival during chick rearing co-vary with the periods of high and low availability of their lipid-rich prey species and whether fishery discards would be an alternative. The proportion of anchovy and sardine in the diet was between 66 and 84% in the years 1986–1988, but just 16–35% from 2004 to 2006. Months with large proportions of anchovy and sardine in the diet were associated with faster chick growth. No association between the proportion of fishery discards in the diet and chick growth was found. The patterns are consistent with the notion that a distributional shift of anchovy and sardine decreased their contribution to the diet of Cape gannets and slowed chick growth along with lessening chick survival at the breeding colony. The reduced survival may partially explain the decline in numbers of Cape gannets breeding in the southern Benguela.

Sexual segregation of common minke whales (Balaenoptera acutorostrata) in Greenland, and the influence of sea temperature on the sex ratio of catches

Laidre, K. L., Heagerty, P. J., Heide-Jorgensen, M. P., Witting, L., Simon, M. — Wed, 04 Nov 2009 08:22:30 PST

Laidre, K. L., Heagerty, P. J., Heide-Jørgensen, M. P., Witting, L., and Simon, M. 2009. Sexual segregation of common minke whales (Balaenoptera acutorostrata) in Greenland, and the influence of sea temperature on the sex ratio of catches. – ICES Journal of Marine Science, 66: 2253–2266.

The harvest of common minke whales (Balaenoptera acutorostrata) in West Greenland has historically been skewed towards female whales, yet a complete analysis of spatial and temporal patterns of catch sex ratio has never been conducted. We examined trends in the sex ratio of catches over time, season, space, and relative to sea temperature using 2400 records from inshore Greenland subsistence whaling operations (1960–2006) and 2072 records from offshore Norwegian commercial operations (1968–1985). Logistic regression models were developed to examine the trend in sex ratio in three regions (Northwest, NW; Central West, CW; Southwest, SW) and by latitude. The highly skewed proportion of females in all catches was strongly positively correlated (r² = 0.8) with latitude in the offshore catches (>100 km). Generalized linear models of inshore catches indicated slightly increasing though non-significant trends in the proportion of females taken off CW and NW Greenland and a significant declining trend off SW Greenland. Sensitivity analyses show that the declining inshore SW trend was entirely accounted for by the past 5 years (2002–2006) of data. Models containing both year and temperature interactions suggested that either parameter provided an equivalent explanation of the variation in trends across regions.

Depletion-corrected average catch: a simple formula for estimating sustainable yields in data-poor situations

MacCall, A. D. — Wed, 04 Nov 2009 08:22:30 PST

MacCall, A. D. 2009. Depletion-corrected average catch: a simple formula for estimating sustainable yields in data-poor situations. – ICES Journal of Marine Science, 66: 2267–2271.

The depletion-corrected average catch (DCAC) formula is an extension of the potential-yield formula, and it provides useful estimates of sustainable yield for data-poor fisheries on long-lived species. Over an extended period (e.g. a decade or more), the catch is divided into a sustainable yield component and an unsustainable "windfall" component associated with a one-time reduction in stock biomass. The size of the windfall is expressed as being equivalent to a number of years of sustainable production, in the form of a "windfall ratio". The DCAC is calculated as the sum of catches divided by the sum of the number of years in the catch series and this windfall ratio. Input information includes the sum of catches and associated number of years, the relative reduction in biomass during that period, the natural mortality rate (M, which should be <0.2 year^–1), and the assumed ratio of F_MSY to M. These input values are expected to be approximate, and based on the estimates of their imprecision, the uncertainty can be integrated by Monte Carlo exploration of DCAC values.

Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially

Kraak, S. B. M., Daan, N., Pastoors, M. A. — Wed, 04 Nov 2009 08:22:30 PST

Kraak, S. B. M., Daan, N., and Pastoors, M. A. 2009. Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially. – ICES Journal of Marine Science, 66: 2272–2277.

Fishing-effort distributions are subject to change, for autonomous reasons and in response to management regulations. Ignoring such changes in a stock-assessment procedure may lead to a biased perception. We simulated a stock distributed over two regions with inter-regional migration and different trends in exploitation and tested the performance of extended survivors analysis (XSA) and a statistical catch-at-age model in terms of bias, when spatially restricted tuning series were applied. If we used a single tuning index that covered only the more heavily fished region, estimates of fishing mortality and spawning-stock biomass were seriously biased. If two tuning series each exclusively covering one region were used (without overlap but together covering the whole area), estimates were also biased. Surprisingly, a moderate degree of overlap of spatial coverage of the two tuning indices was sufficient to reduce bias of the XSA assessment substantially. However, performance was best when one tuning series covered the entire stock area.

The value of information in fisheries management: North Sea herring as an example

Mantyniemi, S., Kuikka, S., Rahikainen, M., Kell, L. T., Kaitala, V. — Wed, 04 Nov 2009 08:22:30 PST

Mäntyniemi, S., Kuikka, S., Rahikainen, M., Kell, L. T., and Kaitala, V. 2009. The value of information in fisheries management: North Sea herring as an example. – ICES Journal of Marine Science, 66: 2278–2283.

We take a decision theoretical approach to fisheries management, using a Bayesian approach to integrate the uncertainty about stock dynamics and current stock status, and express management objectives in the form of a utility function. The value of new information, potentially resulting in new control measures, is high if the information is expected to help in differentiating between the expected consequences of alternative management actions. Conversely, the value of new information is low if there is already great certainty about the state and dynamics of the stock and/or if there is only a small difference between the utility attached to different potential outcomes of the alternative management action. The approach can, therefore, help when deciding on the allocation of resources between obtaining new information and improving management actions. In our example, we evaluate the value of obtaining hypothetically perfect knowledge of the type of stock–recruitment function of the North Sea herring (Clupea harengus) population.

A comparison of two surveys of invertebrates at Pacific Ocean islands: the giant clam at Raivavae Island, Australes Archipelago, French Polynesia

Andrefouet, S., Friedman, K., Gilbert, A., Remoissenet, G. — Mon, 31 Aug 2009 09:05:23 PDT

Andréfouët, S., Friedman, K., Gilbert, A., and Remoissenet, G. 2009. A comparison of two surveys of invertebrates at Pacific Ocean islands: the giant clam at Raivavae Island, Australes Archipelago, French Polynesia. – ICES Journal of Marine Science, 66: 1825–1836.

An assessment of invertebrate fisheries is currently taking place at several Pacific Ocean islands. The objectives are to obtain either detailed information on certain stocks at limited sites or to assess more broadly a variety of benthic resources across different islands. In French Polynesia, giant clam (Tridacna maxima) populations were surveyed by Service de la Pêche and Institut de Recherche pour le Développement (SPE/IRD). Sampling was optimized to determine stock abundance as a tool to enhance management of the clam fishery. Currently, the Secretariat of the Pacific Community (SPC) is investigating throughout the Pacific the status of invertebrate resources; a large-scale study not necessarily establishing a precise stock estimate for resources such as clams, but comparing resource status for several target species using coverage, density, and size measures. Raivavae Island (French Polynesia) was investigated by both programmes and offered an opportunity to verify whether the different sampling schedules provided consistent perspectives of the status of the T. maxima resource. The different strategies that SPE/IRD and SPC adopted resulted in no direct spatial overlap between the locations investigated: nevertheless, the ranges of densities and clam sizes recorded were generally consistent between surveys, and both programmes described similar spatial variation in clam presence at an island scale. SPE/IRD provided a detailed map of clam densities per habitat using a high-resolution satellite image, which yielded an estimated standing stock of 8.16 ± 0.91 million clams, representing a flesh biomass of 354 ± 41 t. SPC's study delivered coverage, density, and clam length, but no stock estimate. Unavailable from SPE/IRD, SPC also described the status of a variety of important invertebrate species targeted by fishers in the Pacific. Both programmes independently made similar fishery management recommendations. The relative merits and complementarities of the two approaches in the context of Pacific Ocean Island resource management are discussed.

Prevalence and seasonality of Hematodinium (Alveolata: Syndinea) in a Scottish crustacean community

Hamilton, K. M., Shaw, P. W., Morritt, D. — Mon, 31 Aug 2009 09:05:23 PDT

Hamilton, K. M., Shaw, P. W., and Morritt, D. 2009. Prevalence and seasonality of Hematodinium (Alveolata: Syndinea) in a Scottish crustacean community. – ICES Journal of Marine Science, 66: 1837–1845.

Protist parasites of the genus Hematodinium were detected in seven crustacean species (Cancer pagurus, Carcinus maenas, Liocarcinus depurator, Munida rugosa, Necora puber, Pagurus bernhardus, and Pagurus prideaux) from the Clyde Sea in Scotland. Seasonal screening of different tissues with sensitive molecular probes showed average infection of 3–23%, with prevalence reaching almost 60% in hermit crabs (P. bernhardus) and brachyuran hosts in spring and >30% in C. pagurus and N. puber in autumn. During summer, Hematodinium infections were rare. Hematodinium seemed to be present in all host sizes sampled. The infection was equally distributed between males and females in most host species, except C. maenas, where males seemed to be more susceptible to infection. PCR amplification of the Hematodinium ribosomal RNA gene in crustacean tissue detected the parasite most frequently in muscle, gills, and heart throughout the 2-year sampling period.

Extracting fish and water velocity from Doppler profiler data

Zedel, L., Cyr-Racine, F.-Y. — Mon, 31 Aug 2009 09:05:23 PDT

Zedel, L., and Cyr-Racine, F-Y. 2009. Extracting fish and water velocity from Doppler profiler data. – ICES Journal of Marine Science, 66: 1846–1852.

Doppler current profilers are optimized for measuring water velocities, but have the demonstrated capability to measure fish swimming speeds. This is possible when fish form schools that are large enough for all multiple Doppler sonar beams to sample the fish speeds at the same time. In situations where fish are not present in at least three acoustic beams, it is impossible to extract fish velocity with the data-processing algorithms normally used to extract water velocity. We present an alternative method of analysing Doppler sonar data that treats data from individual acoustic beams independently, so that velocities can be extracted when fish appear intermittently in the sonar beams. The method determines the variance for each velocity estimate so that data averaging can be adjusted to achieve the desired accuracy. The algorithm is applied to extract both water and fish velocities from Doppler profiler observations of overwintering Atlantic cod (Gadus morhua) in Smith Sound, Newfoundland. Currents in this enclosed coastal area are slow (~10 cm s^–1), and the fish appear to move passively with the water much of the time. However, there are times when the fish have velocities different from those of the water, and profiles averaged over 20 d show clear differences in fish and water velocities.

River plume fronts off NW Iberia from satellite observations and model data

Otero, P., Ruiz-Villarreal, M., Peliz, A. — Mon, 31 Aug 2009 09:05:23 PDT

Otero, P., Ruiz-Villarreal, M., and Peliz, Á. 2009. River plume fronts off NW Iberia from satellite observations and model data. – ICES Journal of Marine Science, 66: 1853–1864.

River plume fronts off NW Iberia during autumn 2002 are examined based on the gradient of the mixed layer depth (MLD) in three-dimensional model data and on sea surface temperature gradients in Advanced Very High Resolution Radiometer (AVHRR) imagery. The method reveals new aspects of the dynamics of fronts in the area. The strong gradient of the MLD between the plume and the adjacent ocean serves as a physical indicator of the maximum extension of the river plume and takes into account its three-dimensional structure as well as its surface signal. Differences in the position of river plume fronts are associated with local upwelling/downwelling conditions and their relaxation. During expansions of the plume induced by upwelling in late autumn, the shallower plume waters become colder and the thermal gradient with offshore waters increases. The model simulation also illustrates the existence of instabilities at the plume front and cross-shore variations in plume width that could induce the appearance of thermal gradients which can be resolved with AVHRR. Our simulations also show regional differences in front location, structure, and probability north (Galicia) and south (north Portugal) on the shelf, where bathymetry differs in shape and depth.

Reproductive ecology of the invasive whelk Rapana venosa Valenciennes, 1846, in the southeastern Black Sea (Gastropoda: Muricidae)

Saglam, H., Duzgunes, E., Ogut, H. — Mon, 31 Aug 2009 09:05:23 PDT

Saglam, H., Düzgünes, E., and Ögüt, H. 2009. Reproductive ecology of the invasive whelk Rapana venosa Valenciennes, 1846, in the southeastern Black Sea (Gastropoda: Muricidae). – ICES Journal of Marine Science, 66: 1865–1867.

The reproductive ecology of the invasive whelk Rapana venosa Valenciennes, 1846 (Gastropoda: Muricidae) was examined in Surmene, southeastern Black Sea, Turkey, using monthly samples of individuals collected by dredging from November 1999 to October 2000. The observed sex ratio (F:M) was 1:1.6; mean shell length at sexual maturity was 40 mm. Changes in the ovary and testis indices indicated that spawning mainly occurred between June and early August in the southeastern Black Sea.

Female reproductive biology, and age of deep-sea squid Histioteuthis miranda from southern Africa

Hoving, H. J. T., Lipinski, M. R. — Mon, 31 Aug 2009 09:05:23 PDT

Hoving, H. J. T., and Lipinski, M. R. 2009. Female reproductive biology, and age of deep-sea squid Histioteuthis miranda from southern Africa. – ICES Journal of Marine Science, 66: 1868–1872.

Data on female reproductive strategy and male and female length–weight relationships and age are presented for the mesopelagic squid Histioteuthis miranda. Females exhibit synchronous ovulation, indicating that eggs are spawned at once or over a short period. The maximum potential fecundity seems to range from 89 000 to 148 000 oocytes. Assuming daily deposition of statolith increments, maturing females were 10–15 months old. Male H. miranda mature young (~6 months) and reach at least 15 months old.

A comparative study of optimization methods and conventional methods for sampling design in fishery-independent surveys

Liu, Y., Chen, Y., Cheng, J. — Mon, 31 Aug 2009 09:05:23 PDT

Liu, Y., Chen, Y., and Cheng, J. 2009. A comparative study of optimization methods and conventional methods for sampling design in fishery-independent surveys. – ICES Journal of Marine Science, 66: 1873–1882.

We have introduced and evaluated a procedure, the constrained spatial simulated annealing method, for developing an optimal sampling design for fishery-independent surveys. We used two criterion functions, minimization of the mean of the shortest distance (MMSD) and uniform distribution of point pairs for variogram estimation (WM), and three arrangements of the two criteria, all WM, all MMSD, and a combination of MMSD (2/3 of samples) and WM (1/3), to construct three optimized sampling designs (denoted as Designs I, II, and III, respectively). These three designs were compared in a simulation study with systematic sampling (Design IV) and stratified random sampling designs (Design V), commonly used in fishery-independent surveys. Three levels of sample size (small, medium, and large) were considered in the simulation study developed using a geostatistical approach. The results showed that for parameter estimation of the spatial covariance function, Design III was better than the other designs at relatively small sample size and Design II performed better than the other designs at relatively large sample size. For estimating fish stock abundance, the performance of the designs considered in this study can be ranked as follows: Design II > Design IV > Design III > Design V > Design I. It is clearly important to evaluate and improve sampling design based on historical survey data. Such a study allows us to identify an optimal sampling design to balance the quality of the data collected and the costs of the sampling programme, leading to the development and optimization of a sustainable and fishery-independent monitoring programme.

Microsatellite analysis of red mullet Mullus barbatus (Perciformes, Mullidae) reveals the isolation of the Adriatic Basin in the Mediterranean Sea

Maggio, T., Lo Brutto, S., Garoia, F., Tinti, F., Arculeo, M. — Mon, 31 Aug 2009 09:05:23 PDT

Maggio, T., Lo Brutto, S., Garoia, F., Tinti, F., and Arculeo, M. 2009. Microsatellite analysis of red mullet Mullus barbatus (Perciformes, Mullidae) reveals the isolation of the Adriatic Basin in the Mediterranean Sea. – ICES Journal of Marine Science, 66: 1883–1891.

The red mullet Mullus barbatus is commercially one of the most important demersal fish resources in the Mediterranean. Molecular data on its genetic population structure throughout the Mediterranean are reported. Six microsatellite loci displayed a high degree of expected heterozygosity and a high allele number per locus. The Hardy–Weinberg equilibrium test revealed an overall tendency towards heterozygote deficiency, probably caused by the admixture of various demes. Population differentiation was assessed by analysis of molecular variance (AMOVA) and Bayesian analysis. AMOVA showed that most of the variation was within the population, but the mean value of F_ST was significant, indicating genetic differentiation among the samples analysed. This differentiation is primarily attributable to the isolation of the Adriatic samples and partly to a weaker substructuring of the populations in the Gulf of Lions, Tyrrhenian Sea, Strait of Sicily, and Ionian Sea. Bayesian analysis also revealed genetic differentiation among the samples analysed, identifying two genetic clusters. The restricted gene flow from and to the Adriatic, also recorded for other fish species, most likely reflects the environmental separation of the Adriatic and suggests that management protocols for the red mullet in the Mediterranean should be revisited.

Modelling seasonal and annual variation in size at functional maturity in the European lobster (Homarus gammarus) from self-sampling data

Laurans, M., Fifas, S., Demaneche, S., Brerette, S., Debec, O. — Mon, 31 Aug 2009 09:05:23 PDT

Laurans, M., Fifas, S., Demaneche, S., Brérette, S., and Debec, O. 2009. Modelling seasonal and annual variation in size at functional maturity in the European lobster (Homarus gammarus) from self-sampling data. – ICES Journal of Marine Science, 66: 1892–1898.

Fishers from Le Croisic (France) measure all the lobsters (Homarus gammarus) they capture, indicating their sex and whether the females are ovigerous or non-ovigerous. Between 2003 and 2006 and mainly between April and September, 16 884 lobsters were measured in this manner. These self-sampled data were used to study catchability and functional maturity of lobsters. The sex ratio was 50%, and catchability did not change if a female was ovigerous or non-ovigerous. With the help of a logistic function, a relationship was established between body size and the proportion of ovigerous females. For the study area, 100% of the females were mature upon reaching a carapace length (CL) of 115 mm, and the proportion of ovigerous females reached 70% each year. The L₅₀ value evolved over a CL of 103–106 mm. From the size when 100% of the females matured (115 mm), there was a larger proportion of ovigerous females than in other studies carried out in more northern European areas.

Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat

Lambert, G., Nielsen, J. R., Larsen, L. I., Sparholt, H. — Mon, 31 Aug 2009 09:05:23 PDT

Lambert, G., Nielsen, J. R., Larsen, L. I., and Sparholt, H. 2009. Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat. – ICES Journal of Marine Science, 66: 1899–1914.

The population dynamics of the Norway pout stock in the North Sea are investigated by statistical analyses, and GIS of ICES International Bottom Trawl Surveys (IBTS) and Danish commercial catch data from 1983 to 2006. The stock spawns mainly around mid-February along the northeastern English and Scottish coasts and between Shetland and Norway. Sex ratios indicate that males, which mature younger than females (age-at-50%-maturity, respectively, 1.2 and 1.5 years), migrate out of the Skagerrak–Kattegat to the spawning grounds before females. There is a decrease in the 2+-group maturity ratios as well as in weight and female length from before to after spawning. The results indicate spawning mortality. Only some 20% of the 1-group reaches maturity in the first quarter, which is higher than assumed in the stock assessment. Although the maturity ogives are variable over time, this difference should be taken into account when estimating spawning-stock biomass in routine assessments. Growth is also variable, with a tendency for male maximum length to be smaller than that of females, and immature fish to be smaller than mature ones in each age group. The juvenile growth rate is higher when the stock density is low and results in a reduced age-at-50%-maturity. Besides these intraspecific patterns, the growth rates show interspecific links to stock sizes of the important predators: cod, haddock, and whiting.

Species identification of Anguilla japonica by real-time PCR based on a sequence detection system: a practical application to eggs and larvae

Minegishi, Y., Yoshinaga, T., Aoyama, J., Tsukamoto, K. — Mon, 31 Aug 2009 09:05:23 PDT

Minegishi, Y., Yoshinaga, T., Aoyama, J., and Tsukamoto, K. 2009. Species identification of Anguilla japonica by real-time PCR based on a sequence detection system: a practical application to eggs and larvae. – ICES Journal of Marine Science, 66: 1915–1918.

To develop a practical method for identifying Japanese eel Anguilla japonica eggs and larvae to species by a sequence detection system using a real-time polymerase chain reaction (PCR), we examined (i) the sensitivity of the system using samples at various developmental stages, and (ii) influences of intra- and interspecific DNA sequence variations in the PCR target region. PCR amplifications with extracted DNA solution at 7.0 ng µl^–1 or lower were efficient at distinguishing A. japonica from other anguillids. A single egg at the gastrula or later developmental stages could also be identified. Two sequence variations in the PCR target region were observed in 2 out of 35 A. japonica collected from three localities, and from four year classes at a single locality. These mutations, however, did not affect the result of species identification achieved by A. japonica-specific PCR primers and probe. The accuracy of this PCR-based method of species identification will help in field surveys of the species.

Preventing overexploitation of migratory fish stocks: the efficacy of marine protected areas in a stochastic environment

West, C. D., Dytham, C., Righton, D., Pitchford, J. W. — Mon, 31 Aug 2009 09:05:23 PDT

West, C. D., Dytham, C., Righton, D., and Pitchford, J.W. 2009. Preventing overexploitation of migratory fish stocks: the efficacy of marine protected areas in a stochastic environment. – ICES Journal of Marine Science, 66: 1919–1930.

Marine protected areas (MPAs) have been widely proposed for protecting overexploited fish populations. It has been suggested that fisheries may be enhanced by spillover of individuals from MPAs into fishing grounds. However, traditional spillover studies fail to account for the seasonal migrations of many populations. Most fisheries models also fail to include the stochasticity inherent in marine environments explicitly. Here we assess MPA efficacy using a simple population model simulating the migration of fish populations between a spawning ground MPA and a fishery. Including realistic environmental stochasticity in our model allows the population to deviate from, and shift between, positive stable equilibria, something that is impossible in a deterministic analysis. This deviation may result in population collapse in cases where deterministic analysis predicts population persistence. We show that, although effective at low migration levels, the ability of MPAs to protect stocks from collapse generally decreases as migration increases. However, an MPA provides greater protection and greater expected fisheries yield than a system without an MPA, irrespective of migration level. Combining MPAs with a harvest control rule may further increase protection and yield. We therefore argue that MPAs can play a role in the protection of migratory species.

Different responses to area closures and effort controls for sedentary and migratory harvested species in a multispecies coral reef linefishery

Little, L. R., Punt, A. E., Mapstone, B. D., Begg, G. A., Goldman, B., Ellis, N. — Mon, 31 Aug 2009 09:05:23 PDT

Little, L. R., Punt, A. E., Mapstone, B. D., Begg, G. A., Goldman, B., and Ellis, N. 2009. Different responses to area closures and effort controls for sedentary and migratory harvested species in a multispecies coral reef linefishery. – ICES Journal of Marine Science, 66: 1931–1941.

We used a simulation model to examine the effect of area closures and fishing effort on the two main target species of the Great Barrier Reef Coral Reef Finfish Fishery: common coral trout (Plectropomus leopardus) and red throat emperor (Lethrinus miniatus). Area closures had greater effect on the more sedentary coral trout, in the areas outside the closures and accessible to the fishery, and little effect on red throat emperor, which was assumed to move among reefs. The effects of effort levels were greater than area closures on the harvest of both species and were seen not only in the areas accessible to the fishery, but also in the biomass of red throat emperor in the areas closed to the fishery. The catch and biomass resulting from a given effort level did not appear to have an equivalent effect attributable to any area closure. Although the effects of effort levels and area closures are confounded in reality by the coincidental implementation of area closures and restructuring of the fishery, the simulation model separated these factors to show that the closures under the 2004 rezoning should have had minimal effect on total-stock biomass and that a greater effect would result from changes in fishing effort.

Long-term seasonal and spatial patterns in mortality and survival of Calanus finmarchicus across the Atlantic Zone Monitoring Programme region, Northwest Atlantic

Plourde, S., Pepin, P., Head, E. J. H. — Mon, 31 Aug 2009 09:05:23 PDT

Plourde, S., Pepin, P., and Head, E. J. H. 2009. Long-term seasonal and spatial patterns in mortality and survival of Calanus finmarchicus across the Atlantic Zone Monitoring Programme region, Northwest Atlantic. – ICES Journal of Marine Science, 66: 1942–1958.

The vertical life table method was used to estimate stage-specific daily mortality rates and survival from 1999 to 2006 for Calanus finmarchicus sampled in the Canadian Atlantic Zone Monitoring Programme, which covers the Newfoundland–Labrador Shelf (NLS), Gulf of St Lawrence (GSL), and Scotian Shelf (SS). Stage-specific mortality rates and survival showed significant regional and seasonal differences, with the largest signal associated with variations in temperature. Density-dependent mortality, associated with the abundance of C6 females, was the main factor influencing mortality in the egg–C1 transition during the period of population growth in spring on the SS, and in summer in the GSL and on the NLS. In autumn, mortality in egg–C1 was positively related to temperature and negatively related to phytoplankton biomass, with particularly high mortality rates on the SS. The integration of our results into stage-specific recruitment rates from egg to C5 revealed that C. finmarchicus populations experience their greatest loss (mortality) during the egg–C1 transition. Loss during development to C1 was greater in the GSL than in the other regions during the period of population growth, resulting in lower recruitment success in the GSL. In autumn, C. finmarchicus showed low stage-specific daily recruitment rates on the SS at high temperatures, and low phytoplankton biomass compared with those in the GSL and on the NLS. Our findings reinforce the necessity of describing regional and seasonal patterns in mortality and survival to understand factors controlling the population dynamics of C. finmarchicus.

Using stock assessment information to assess fishing capacity of tuna fisheries

Arrizabalaga, H., Restrepo, V. R., Maunder, M. N., Majkowski, J. — Mon, 31 Aug 2009 09:05:23 PDT

Arrizabalaga, H., Restrepo, V. R., Maunder, M. N., and Majkowski, J. 2009. Using stock assessment information to assess fishing capacity of tuna fisheries. – ICES Journal of Marine Science, 66: 1959–1966.

In tuna and tuna-like fisheries, there is a need for periodic assessments of fishing capacity to aid management. However, the nature and quantity of data needed to apply conventional methodologies for estimating fishing capacity are not usually available for tuna fisheries. We discuss simple alternative approaches to estimate fishing capacity and related quantities (i.e. capacity utilization, excess capacity, and overcapacity) directly from stock assessment inputs and outputs that are usually available for most tuna (and many other) stocks. Sensitivity analyses are performed to assess the effect of different levels of data aggregation and different assumptions made during the stock assessments on estimates of fishing capacity. Main advantages and disadvantages of the proposed methodologies are also illustrated using stock assessment information from different tuna stocks with different historical developments and trends in fishing mortality.

Bottom temperature and in situ development of chokka squid eggs (Loligo vulgaris reynaudii) on mid-shelf spawning grounds, South Africa

Oosthuizen, A., Roberts, M. J. — Mon, 31 Aug 2009 09:05:23 PDT

Oosthuizen, A., and Roberts, M. J. 2009. Bottom temperature and in situ development of chokka squid eggs (Loligo vulgaris reynaudii) on mid-shelf spawning grounds, South Africa. – ICES Journal of Marine Science, 66: 1967–1971.

The aim of the study was to test the development success of squid eggs on the mid-shelf (60–150 m deep) spawning grounds in relation to previous laboratory results, and to describe the mid-shelf temperature environment and how it could affect egg development. A series of in situ egg incubation experiments was conducted on the mid-shelf (~119 m deep) spawning grounds using cages, temperature sensors, and acoustic releases for retrieval. Newly spawned eggs were collected by scuba, and continuous temperature data were collected at two points between the known inshore spawning grounds and the mid-shelf areas. Temperature variations followed a seasonal warming and cooling cycle, with superimposed peaks and troughs. Egg development data indicated that warm temperature peaks (10–13°C) are sufficient for normal development of eggs on the mid-shelf. Egg development time on the mid-shelf was 2–3 times longer (50–60 vs. 20–30 d) than inshore. The scarcity of abnormalities (0.45%) disputes previous laboratory results that suggested that ~50% of eggs would suffer abnormalities in the colder mid-shelf temperature environment.

Variability in the relationship between sea scallop shell height and meat weight

Rothschild, B. J., Adams, C. F., Sarro, C. L., Stokesbury, K. D. E. — Mon, 31 Aug 2009 09:05:23 PDT

Rothschild, B. J., Adams, C. F., Sarro, C. L., and Stokesbury, K. D. E. 2009. Variability in the relationship between sea scallop shell height and meat weight. – ICES Journal of Marine Science, 66: 1972–1977.

We investigated the spatial and temporal variability in the relationship between shell height and meat weight (SHMW) of the sea scallop (Placopecten magellanicus) from Georges Bank (GB) and the mid-Atlantic. Data for the study were collected collaboratively during normal commercial fishing operations. A one-way random-effects ANOVA revealed that 19–44% of the variance in MW was at the batch level. A linear mixed-effects model was used to explain the variability in SHMW regression equations across batches. There was a significant effect of month and year on the SHMW relationship for GB from June through December, and a significant effect of area and year on the SHMW relationship for the mid-Atlantic from January through May. The SHMW relationships presented reflect those of the fishery year-round rather than an estimate of the biological population at a specific point in time. Failure to include intra-annual, interannual, and regional variations in the SHMW could result in continually over- or underestimating the allowable catch in areas open to fishing for short periods. The techniques used are applicable to length–weight studies in general.

How community ecology links natural mortality, growth, and production of fish populations

Andersen, K. H., Farnsworth, K. D., Pedersen, M., Gislason, H., Beyer, J. E. — Mon, 31 Aug 2009 09:05:23 PDT

Andersen, K. H., Farnsworth, K. D., Pedersen, M., Gislason, H., and Beyer, J. E. 2009. How community ecology links natural mortality, growth, and production of fish populations. – ICES Journal of Marine Science, 66: 1978–1984.

Size-spectrum theory is used to show that (i) predation mortality is a decreasing function of individual size and proportional to the consumption rate of predators; (ii) adult natural mortality M is proportional to the von Bertalanffy growth constant K; and (iii) productivity rate P/B is proportional to the asymptotic weight W^–1/3. The constants of proportionality are specified using individual level parameters related to physiology or prey encounter. The derivations demonstrate how traditional fisheries theory can be connected to community ecology. Implications for the use of models for ecosystem-based fisheries management are discussed.

Modelling the direct impact of bottom trawling on the North Sea fish community to derive estimates of fishing mortality for non-target fish species

Piet, G. J., van Hal, R., Greenstreet, S. P. R. — Mon, 31 Aug 2009 09:05:23 PDT

Piet, G. J., van Hal, R., and Greenstreet, S. P. R. 2009. Modelling the direct impact of bottom trawling on the North Sea fish community to derive estimates of fishing mortality for non-target fish species. – ICES Journal of Marine Science, 66: 1985–1998.

This study introduces a spatially explicit model that combines abundance data for all the main fish species in the demersal North Sea fish community with international effort data and estimates of gear-, species-, and size-dependent catch efficiency to determine the mortality of non-target fish species caused by bottom trawl fisheries and its spatial variation. Where necessary information was lacking, assumptions were made, and a sensitivity analysis performed to examine the impact of these issues on model results. Model outcomes were validated using international landings and discard data for five target species: cod, haddock, whiting, sole, and plaice. This showed that depending on its configuration, the model could reproduce recorded landings and discards of these species reasonably well. This suggests that the model could be used to simulate rates of fishing mortality for non-target fish species, for which few data are currently available. Sensitivity analyses revealed that model outcomes were most strongly influenced by the estimates of gear catch efficiency and the extent to which the distributions of fishing effort and each species overlapped. Better data for these processes would enhance the contribution that this type of model could make in supporting an ecosystem approach to fisheries management.

A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method

Mon, 31 Aug 2009 09:05:23 PDT

van Damme, C. J. G., Bolle, L. J., Fox, C. J., Fossum, P., Kraus, G., Munk, P., Rohlf, N., Witthames, P. R., and Dickey-Collas, M. 2009. A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method. – ICES Journal of Marine Science, 66: 1999–2011.

Uncertainty about the quality of current virtual population analysis-based stock assessment for North Sea plaice (Pleuronectes platessa) has led to various abundance indices. We compared biomass estimates from the annual egg production (AEP) method with current stock assessments based on catch-at-age to validate the current and historical perception of exploitation. The AEP method was also used to investigate the dynamics of the spatial components of plaice in the North Sea. We corrected for fecundity down-regulation and changes in sex ratio. Estimates from both methods were similar in trend and absolute biomass. On the Dogger Bank, there was a dramatic decline in biomass from 1948 and 1950 to 2004, and in the Southern Bight, the stock appeared to increase from 1987 and 1988 to 2004, although not reaching the historically high levels of 1948 or 1950. The timing of spawning of North Sea plaice does not appear to have changed throughout the period of high exploitation. We conclude that the AEP method is a useful way to hindcast the spatial dynamics of heavily exploited flatfish stocks.

Sediment-biota interactions and mapping marine habitats: an Introduction

Noji, T., Rumohr, H., Smith, S. J. — Mon, 31 Aug 2009 09:05:23 PDT

Noji, T., Rumohr, H., and Smith, S. J. 2009. Sediment–biota interactions and mapping marine habitats: an Introduction. – ICES Journal of Marine Science, 66: 2012.

Seabed mapping for selecting cold-water coral protection areas on Hatton Bank, Northeast Atlantic

Mon, 31 Aug 2009 09:05:23 PDT

Durán Muñoz, P., Sayago-Gil, M., Cristobo, J., Parra, S., Serrano, A., Díaz del Rio, V., Patrocinio, T., Sacau, M., Murillo, F. J., Palomino, D., and Fernández-Salas, L. M. 2009. Seabed mapping for selecting cold-water coral protection areas on Hatton Bank, Northeast Atlantic. – ICES Journal of Marine Science, 66: 2013–2025.

Research into vulnerable marine ecosystems (VMEs) on the high seas and the impacts of bottom fishing and ad hoc management measures are high priority today thanks to UN General Assembly Resolution 61/105. An interdisciplinary methodology (specifically designed for selecting cold-water coral protection areas) and a case study focused on the Hatton Bank (NE Atlantic) are presented. This interdisciplinary approach, developed under the ECOVUL/ARPA project, was based on conventional fisheries science, geomorphology, benthic ecology, and sedimentology. It contributes to defining practical criteria for identifying VMEs, to improving knowledge of their distribution off Europe's continental shelf, and to providing advice on negative fishing impacts and habitat protection. The approach was used to identify the bottom-trawl deep-sea fishery footprint on the western slope of Hatton Bank, to map the main fishing grounds and related deep-sea habitats (1000–1500 m deep), and to study the interactions between fisheries and cold-water corals. The results lead to a proposal to close the outcrop area (4645 km²) located on the western slope of Hatton Bank as a conservation measure for cold-water corals.

Prediction of benthic biotopes on a Norwegian offshore bank using a combination of multivariate analysis and GIS classification

Buhl-Mortensen, P., Dolan, M., Buhl-Mortensen, L. — Mon, 31 Aug 2009 09:05:23 PDT

Mortensen, P. B., Dolan, M., and Buhl-Mortensen, L. 2009. Prediction of benthic biotopes on a Norwegian offshore bank using a combination of multivariate analysis and GIS classification. – ICES Journal of Marine Science, 66: 2026–2032.

This study is part of the multidisciplinary seabed mapping programme MAREANO (Marine AREAdatabase for NOrwegian coast and sea areas). The mapping programme includes acquisition of multibeam bathymetry and acoustic backscatter data together with a comprehensive, integrated biological and geological sampling programme. The equipment used includes underwater video, boxcorer, grab, hyperbenthic sled, and beam trawl. The Tromsøflaket offshore bank was used as a case-study area to develop suitable methods for mapping habitats and biotopes. A procedure for producing maps of predicted biotopes is described that combined information on the distribution of biological communities with environmental factors and indicators. Detrended correspondence analysis (DCA) was used to relate bottom environment [including multiscale physical descriptors of the seabed derived from multibeam echosounder (MBES) data] and faunal distribution to find the best physical biotope descriptors. DCA of 252 video samples (sequences 200 m long) revealed six groups of locations representing different biotopes. These were characterized by different compositions of species, substrata, depths, and values for terrain parameters. Prediction of biotope distribution was performed using a supervised GIS classification with the MBES-derived physical seabed descriptors with the strongest explanatory ability (depth, backscatter, and broad-scale bathymetric position index) identified by the DCA. The species diversity of the identified biotopes was described from the content of the bottom samples. For future MAREANO cruises, an important task will be to ground-truth predictions of habitat and biotopes and to test the reliability of these predictions in the wider MAREANO area.

The role of marine habitat mapping in ecosystem-based management

Cogan, C. B., Todd, B. J., Lawton, P., Noji, T. T. — Mon, 31 Aug 2009 09:05:23 PDT

Cogan, C. B., Todd, B. J., Lawton, P., and Noji, T. T. 2009. The role of marine habitat mapping in ecosystem-based management. – ICES Journal of Marine Science, 66: 2033–2042.

Ecosystem-based management (EBM) and the related concept of large marine ecosystems (LMEs) are sometimes criticized as being too broad for many management and research applications. At the same time, there is a great need to develop more effectively some substantive scientific methods to empower EBM. Marine habitat mapping (MHM) is an example of an applied set of field methods that support EBM directly and contribute essential elements for conducting integrated ecosystem assessments. This manuscript places MHM practices in context with biodiversity models and EBM. We build the case for MHM being incorporated as an explicit and early process following initial goal-setting within larger EBM programmes. Advances in MHM and EBM are dependent on evolving technological and modelling capabilities, conservation targets, and policy priorities within a spatial planning framework. In both cases, the evolving and adaptive nature of these sciences requires explicit spatial parameters, clear objectives, combinations of social and scientific considerations, and multiple parameters to assess overlapping viewpoints and ecosystem functions. To examine the commonalities between MHM and EBM, we also address issues of implicit and explicit linkages between classification, mapping, and elements of biodiversity with management goals. Policy objectives such as sustainability, ecosystem health, or the design of marine protected areas are also placed in the combined MHM–EBM context.

The impact of commercial fishing on the determination of habitat associations for sea scallops (Placopecten magellanicus, Gmelin)

Smith, S. J., Black, J., Todd, B. J., Kostylev, V. E., Lundy, M. J. — Mon, 31 Aug 2009 09:05:23 PDT

Smith, S. J., Black, J., Todd, B. J., Kostylev, V. E. and Lundy, M. J. 2009. The impact of commercial fishing on the determination of habitat associations for sea scallops (Placopecten magellanicus, Gmelin). – ICES Journal of Marine Science, 66: 2043–2051.

The sea scallop (Placopecten magellanicus) population off southwestern Nova Scotia in Scallop Fishing Area 29 has been monitored by an annual drag survey since the fishery started there in 2001. A new stratification scheme based on surficial geology maps from a multibeam bottom mapping and geology ground-truth project completed in 2004 in the area have been used for survey design since 2005. Survey data from before 2005 have been post-stratified using the new strata. The efficiency of the design with respect to variance reduction appears to have diminished over time suggesting that the association between scallop abundance and bottom type may not have been as strong or constant as first assumed. Modelling of the association between scallop abundance and bottom type and depth using a Bayesian hierarchical approach confirms this diminishing relationship. Comparison of the results from the model with spatial measures of fishing effort based on satellite vessel monitoring data suggests that increasing exploitation may be masking the relationships as scallop beds are targeted and fished down. These results could have implications on the interpretation of species habitat associations from areas where data are only available from periods when the populations have been exploited over a long time. In these cases, the spatial distribution of fishing effort may be a better indicator of species habitat associations than the estimates from surveys.

Investigating the link between Nephrops norvegicus burrow density and sediment composition in Scottish waters

Campbell, N., Allan, L., Weetman, A., Dobby, H. — Mon, 31 Aug 2009 09:05:23 PDT

Campbell, N., Allan, L., Weetman, A., and Dobby, H. 2009. Investigating the link between Nephrops norvegicus burrow density and sediment composition in Scottish waters. – ICES Journal of Marine Science, 66: 2052–2059.

Nephrops norvegicus is a burrowing decapod, found in the North Atlantic and Mediterranean Sea at depths of 10–1200 m, and currently the most valuable species taken by the commercial fishing industry in Scotland. It constructs and inhabits extensive burrow complexes in suitable muddy sediments. Owing to its variable emergence patterns, catch rates from traditional trawl surveys are not considered a good indicator of population size. Nephrops populations around Scotland are assessed using an underwater television (UWTV) survey method. Sediment samples are collected at the end of each UWTV deployment. This study focuses on two areas off the coast of Scotland and investigates the accuracy of the sediment maps used for assessment purposes, and the relationship between Nephrops burrow density and sediment composition, over the period 2002–2007. Nephrops have a stock-specific relationship with the sediment they inhabit, which retains the same form through fluctuations in population size.

Associations of lobsters (Homarus americanus) off southwestern Nova Scotia with bottom type from images and geophysical maps

Tremblay, M. J., Smith, S. J., Todd, B. J., Clement, P. M., McKeown, D. L. — Mon, 31 Aug 2009 09:05:24 PDT

Tremblay, M. J., Smith, S. J., Todd, B. J., Clement, P. M., and McKeown, D. L. 2009. Associations of lobsters (Homarus americanus) off southwestern Nova Scotia with bottom type from images and geophysical maps. – ICES Journal of Marine Science, 66: 2060–2067.

Images from an underwater towed vehicle (Towcam) were used to estimate densities and to evaluate bottom-type associations of lobsters (Homarus americanus), crabs (Cancer spp.), and scallops (Placopecten magellanicus). Images were obtained in October 2006 along 14 line-transects off southwestern Nova Scotia in an area with productive lobster and scallop fisheries. Lobsters were observed in 4% of the 2044 images, crabs in 7%, and scallops in 40%. On sand, gravel, and cobble seabed, lobsters were readily observable. On rougher substrata with boulders, some lobsters were still evident either in the open or partially hidden in shelters. Estimated densities of lobsters from the images on some transects were 0.04 m^–2, approximately half of the estimates of lobster density for adjacent inshore areas from scuba, but 34 times higher than estimates from scallop drags in the same area. Models of animal presence by bottom type were evaluated with categories that were (i) geophysically based (map of bottom type from geophysical characteristics) and (ii) image-based (sediment size from images). Significant relationships were evident with both types of seabed categorization, suggesting that it would be beneficial to stratify surveys using geophysical categories. Depth was also significant in determining presence/absence of lobsters and crabs. There is potential to develop indicators of lobster abundance using underwater imaging, and stratification by bottom type should be incorporated into surveys.

Spatial prediction of demersal fish distributions: enhancing our understanding of species-environment relationships

Moore, C. H., Harvey, E. S., Van Niel, K. P. — Mon, 31 Aug 2009 09:05:24 PDT

Moore, C. H., Harvey, E. S., and Van Niel, K. P. 2009. Spatial prediction of demersal fish distributions: enhancing our understanding of species–environment relationships. – ICES Journal of Marine Science, 66: 2068–2075.

We used species distribution modelling to identify key environmental variables influencing the spatial distribution of demersal fish and to assess the potential of these species–environment relationships to predict fish distributions accurately. In the past, predictive modelling of fish distributions has been limited, because detailed habitat maps of deeper water (>10 m) have not been available. However, recent advances in mapping deeper marine environments using hydroacoustic surveys have redressed this limitation. At Cape Howe Marine National Park in southeastern Australia, previously modelled benthic habitats based on hydroacoustic and towed video data were used to investigate the spatial ecology of demersal fish. To establish the influence of environmental variables on the distributions of this important group of marine fish, classification trees (CTs) and generalized additive models (GAMs) were developed for four demersal fish species. Contrasting advantages were observed between the two approaches. CTs provided greater explained variation for three of the four species and revealed a better ability to model species distributions with complex environmental interactions. However, the predictive accuracy of the GAMs was greater for three of the four species. Both these modelling techniques provided a detailed understanding of demersal fish distributions and landscape linkages and an accurate method for predicting species distributions across unsampled locations where continuous spatial benthic data are available. Information of this nature will permit more-targeted fisheries management and more-effective planning and monitoring of marine protected areas.

"Linking Herring": do we really understand plasticity?

Dickey-Collas, M., Clarke, M., Slotte, A. — Mon, 17 Aug 2009 09:10:35 PDT

Dickey-Collas, M., Clarke, M., and Slotte, A. 2009. "Linking Herring": do we really understand plasticity? – ICES Journal of Marine Science, 66: 1649–1651.

Herring and ICES: a historical sketch of a few ideas and their linkages

Sinclair, M. — Mon, 17 Aug 2009 09:10:36 PDT

Sinclair, M. 2009. Herring and ICES: a historical sketch of a few ideas and their linkages. – ICES Journal of Marine Science, 66: 1652–1661.

This introduction to the Symposium on "Linking Herring" sketches the development of some ideas generated from herring research within an ICES context. The work of Committee A (1902–1908), under the leadership of Johan Hjort, led to a paradigm shift from "migration thinking" to "population thinking" as the interpretation of fluctuations in herring landings. From the 1920s to the 1950s, the focus on forecasting services for the herring fisheries, although ultimately unsuccessful, had the unintended consequence of generating ideas on recruitment overfishing and the match–mismatch hypothesis. The collapse of the East Anglian fishery led, in 1956, to considerable debate on its causes, but no consensus was reached. Three consecutive symposia dealing with herring (1961, 1968, and 1970) reveal a changing perspective on the role of fishing on recruitment dynamics, culminating in Cushing’s 1975 book ("Marine Ecology and Fisheries", referred to here as the "Grand Synthesis"), which defined the concept of recruitment overfishing and established the future agenda for fisheries oceanography. The 1978 ICES "Symposium on the Assessment and Management of Pelagic Fish Stocks" is interpreted as the "Aberdeen Consensus" (i.e. without effective management, recruitment overfishing is to be expected). In conclusion, herring research within ICES has led to many ideas and two major paradigm shifts.

Spatial diversity of Pacific herring (Clupea pallasi) spawning areas

Hay, D. E., McCarter, P. B., Daniel, K. S., Schweigert, J. F. — Mon, 17 Aug 2009 09:10:36 PDT

Hay, D. E., McCarter, P. B., Daniel, K. S., and Schweigert, J. F. 2009. Spatial diversity of Pacific herring (Clupea pallasi) spawning areas. – ICES Journal of Marine Science, 66: 1662–1666.

Eastern Pacific herring spawn in intertidal and shallow subtidal areas. Spawning sites are conspicuous: milt turns coastal waters white, sometimes for distances of many kilometres. This attribute has enabled biologists to document spawning distributions for more than 70 years throughout the 29 500 km coastline of western Canada. Spawning distributions and spatial diversity have varied over time. When aggregated over 70 years (1938–2007), spawning occurred along 5574 km or ~20% of the total coastline. Cumulative annual spawn length ranges from 131 (in 1966) to 770 km (in 1992). We examined annual changes in spawn distribution using spatial units of variable size, ranging in area from a maximum of >1000 km² to a minimum of <0.1 km². Assessment of spatial diversity varied with the size of the spatial unit. Spatial diversity estimated from small spatial units (area <0.1 km²) was significantly correlated with spawning-stock biomass (SSB). In contrast, there was no correlation, and sometimes opposite temporal trends, between SSB and all larger spatial units (mean area >0.3 km²). The choice of spatial scale can affect the results from analyses of other factors, such as SSB, that could affect spatial diversity of spawning areas.

When is year-class strength determined in western Baltic herring?

Mon, 17 Aug 2009 09:10:36 PDT

Oeberst, R., Klenz, B., Gröhsler, T., Dickey-Collas, M., Nash, R. D. M., and Zimmermann, C. 2009. When is year-class strength determined in western Baltic herring? – ICES Journal of Marine Science, 66: 1667–1672.

Weekly surveys of larvae in the Strelasund and the Greifswalder Bodden were used to investigate when year-class strength is determined in western Baltic spring-spawning (WBSS) herring. An abundance metric of larvae reaching a length of 20 mm over the entire spawning season was constructed by accounting for increases in daily growth resulting from seasonal increases in temperature (5–20°C). The index was significantly correlated with the acoustic estimates of age-1 herring in the western Baltic Sea (r = 0.88) and with the estimates of year-class strength obtained from stock assessment (r = 0.65). Previous studies of herring elsewhere have reported that year-class strength is determined during the late larval stage, but we show that year-class strength can already be fixed at a larval length of only 20 mm. Although the index obtained may be used in stock assessment and predictions, the intriguing question remains, namely how can the signal of larval productivity from one single spawning component of WBSS herring reflect the year-class dynamics of the entire stock?

Finding the signal in the noise: objective data-selection criteria improve the assessment of western Baltic spring-spawning herring

Payne, M. R., Clausen, L. W., Mosegaard, H. — Mon, 17 Aug 2009 09:10:36 PDT

Payne, M. R., Clausen, L. W., and Mosegaard, H. 2009. Finding the signal in the noise: objective data-selection criteria improve the assessment of western Baltic spring-spawning herring. – ICES Journal of Marine Science, 66: 1673–1680.

In the art of fish-stock assessment, it is common practice to include all available data without properly testing their validity in terms of their signal-to-noise ratio. The western Baltic spring-spawning herring (Clupea harengus) stock has been historically difficult to assess in a reliable manner. The population is spread between the Skagerrak, Kattegat, the Danish islands, and the western Baltic, but the distribution depends on age and season. Although the distribution area is covered by five separate surveys, none covers the entire stock. Using all time-series data may cause high noise levels and could lead to a poor-quality assessment. We examine the temporal and spatial coverage of each survey in terms of current biological understanding of stock distribution and, employing the observed internal consistency between age classes within cohorts as additional criteria, select the most appropriate data subsets. Assessments based on the revised dataset show greatly improved quality in terms of both accuracy and precision. The results highlight the often-ignored principle that a judicious choice of input data, based on rational and justifiable selection criteria, can enhance the ultimate quality of a stock assessment.

Recruitment forecasting using indices of young-of-the-year Pacific herring (Clupea pallasi) abundance in the Strait of Georgia (BC)

Schweigert, J. F., Hay, D. E., Therriault, T. W., Thompson, M., Haegele, C. W. — Mon, 17 Aug 2009 09:10:36 PDT

Schweigert, J. F., Hay, D. E., Therriault, T. W., Thompson, M., and Haegele, C. W. 2009. Recruitment forecasting using indices of young-of-the-year Pacific herring (Clupea pallasi) abundance in the Strait of Georgia (BC). – ICES Journal of Marine Science, 66: 1681–1687.

Within the Strait of Georgia (BC, Canada), recruitment of Pacific herring (Clupea pallasi) to the spawning stock at age 3 can be highly variable, and this component may compose a major portion of the spawning-stock biomass. Therefore, a reliable method of forecasting recruitment strength would be useful for determining total allowable catches for the fishery. We developed an empirical approach to forecasting recruitment from young-of-the-year (YOY) surveys using purse-seine sampling in late September and evaluate its predictive capability for estimating the relative size of a year class before it enters the fishery. For each year, we compared YOY catches-by-weight with the number of age-3 recruits derived from subsequent catch-at-age analyses. The relationship is positive but not statistically significant because of considerable annual variation in the estimates. However, it is worth noting that in years when YOY herring were least abundant, the resulting cohort also was low. Consequently, although the relationship may not be sufficiently precise for accurate recruitment forecasting, it can be used by fishery management for the qualitative evaluation of the likelihood of strong or weak returns in future seasons when setting quotas for the fishery.

Advances in herring biology: from simple to complex, coping with plasticity and adaptability

Geffen, A. J. — Mon, 17 Aug 2009 09:10:36 PDT

Geffen, A. J. 2009. Advances in herring biology: from simple to complex, coping with plasticity and adaptability. – ICES Journal of Marine Science, 66: 1688–1695.

At least two centuries of investigations on herring have been absorbed by scientific journals, and applied and basic research has produced groundbreaking concepts in fisheries, population biology, and marine ecology. By the 1970s, a firm understanding of herring biology formed the basis for more sophisticated research. At that point, herring populations had been delineated, and their migration patterns described. The reproduction and early stage biology were characterized in ways that could be applied to fisheries management. However, over the subsequent four decades, new approaches and technology overturned many of the earlier findings. Behavioural studies revealed a repertoire of patterns that extended the concept of schooling, and genetic analyses showed high levels of stock mixing. Application of otolith analysis to larval, juvenile, and adult fish revealed the scope of plasticity in growth and life-history strategies. Developments in physiological research have revealed that herring are not "primitive", as once believed, but highly adaptable in their nutrition and metabolism. These advances fundamentally changed our view of herring, and the resulting challenge is to synthesize current knowledge to help explain the significance of adaptability and plasticity in its flexible life history.

Mean daily growth of herring larvae in relation to temperature over a range of 5-20{degrees}C, based on weekly repeated cruises in the Greifswalder Bodden

Oeberst, R., Dickey-Collas, M., Nash, R. D. M. — Mon, 17 Aug 2009 09:10:36 PDT

Oeberst, R., Dickey-Collas, M., and Nash, R. D. M. 2009. Mean daily growth of herring larvae in relation to temperature over a range of 5–20°C, based on weekly repeated cruises in the Greifswalder Bodden. – ICES Journal of Marine Science, 66: 1696–1701.

Reported estimates of mean daily growth of herring larvae generally cover the temperature range 1–12°C and few estimates are available for temperatures >15°C. We use larval surveys on Rügen spring-spawning herring in the Strelasund and the Greifswalder Bodden to estimate larval growth over a wider temperature range because the water temperature in that area normally increases from 5 to 20°C during the larval growth period (i.e. from spring to summer). This large temperature increase has a significant influence on the mean daily growth of herring larvae. Growth estimates were based on the modes of length frequencies observed at individual stations or accumulated over strata from consecutive surveys. Mean daily growth (G; mm d^–1) of larvae was primarily determined by the ambient temperature (T) during the growth interval (5–7 d), resulting in the following relationship: G = 0.011 + 0.037 T. A non-linear function is also described. Growth rate was not length-dependent over the size range studied (5–20 mm). The study also showed that herring larvae were growing and surviving in temperatures up to 17.5°C.

Effects of prey concentration, light regime, and parental origin on growth and survival of herring larvae under controlled experimental conditions

Folkvord, A., Hoie, H., Johannessen, A., Solbakken, T. — Mon, 17 Aug 2009 09:10:36 PDT

Folkvord, A., Høie, H., Johannessen, A., and Solbakken, T. 2009. Effects of prey concentration, light regime, and parental origin on growth and survival of herring larvae under controlled experimental conditions. – ICES Journal of Marine Science, 66: 1702–1709.

Experiments were undertaken to study the combined effects of environmental (prey concentration and photoperiod) and genetic (parental spawning season) factors on growth and survival of herring larvae. During the experimental period, constant prey concentrations were maintained at one of the two nominal levels, under either a spring or an autumn light regime. Eggs of one autumn-spawning North Sea Buchan female herring were fertilized either with cryopreserved sperm from three Norwegian spring-spawning males or with fresh sperm from three Buchan males. Larvae of the two groups (the hybrids marked with alizarin) were mixed in replicated treatment tanks, thus ensuring identical environmental conditions. Mean larval growth rates were mostly influenced by food availability, but the hybrids grew significantly faster than the pure autumn-spawned offspring. In addition, the hybrids experienced a survival advantage at low prey concentrations. Hybrid survival was also somewhat better at high prey concentrations under a spring photoperiod than the corresponding group under an autumn photoperiod, suggesting a possible genetic adaptation to seasonal light conditions. The experiment documents the viability beyond first-feeding of offspring from parents with different spawning periods. The results are discussed in relation to herring metapopulation structure.

Effects of hatching time on year-class strength in Norwegian spring-spawning herring (Clupea harengus)

Mon, 17 Aug 2009 09:10:36 PDT

Husebø, Å., Stenevik, E. K., Slotte, A., Fossum, P., Salthaug, A., Vikebø, F., Aanes, S., and Folkvord, A. 2009. Effects of hatching time on year-class strength in Norwegian spring-spawning herring (Clupea harengus). – ICES Journal of Marine Science, 66: 1710–1717.

Effects of mean hatching date, post-hatching temperature, wintering temperature of adults, spawning stock size, and percentage of recruit spawners on larval survival in Norwegian spring-spawning herring (Clupea harengus) during the period 1987–2004 were analysed. In the final model, only hatching date proved to be significant. However, hatching date was itself negatively correlated with wintering temperature and positively correlated with the percentage of recruit spawners. This suggests indirect effects on larval survival, whereby low percentages of recruit spawners and high temperatures during gonad development lead to early spawning. Early hatching could be favourable for survival by allowing the larvae to drift away from areas where potential predators concentrate in spring, before predation pressure increases. Indirect support for this hypothesis was found in the activity of the purse-seine fishery for immature saithe (Pollachius virens) along the Norwegian coast. This fishery starts as soon as the saithe aggregate into large schools, which is presumed to reflect their feeding activity. The commercial catch data indicated that the saithe became active 2 months earlier in the area south of 67°N, than in areas to the north. Both field data and larval drift models confirmed that the majority of the early hatched larvae had passed across this border by that time of year.

Progress in modelling herring populations: an individual-based model of growth

Mon, 17 Aug 2009 09:10:36 PDT

Russo, T., Mariani, S., Baldi, P., Parisi, A., Magnifico, G., Clausen, L. W., and Cataudella, S. 2009. Progress in modelling herring populations: an individual-based model of growth. – ICES Journal of Marine Science, 66: 1718–1725.

Stock assessment may gain from taking into account individual variations in growth, because size is a key predictor of survival and reproduction. In trying to understand patterns in empirical observations, a major challenge is to model the changes in the size distribution of a cohort with age. We introduce an individual-based growth model that is founded on the use of a stochastic class of processes called subordinators. This modelling approach has several desirable features, because it (i) can take account of both individual and environmental sources of random variations, (ii) has the property of letting size increase monotonically, and (iii) ensures that the mean size-at-age follows the widely accepted von Bertalanffy equation. The parameterization of the model is tested on two Atlantic herring (Clupea harengus) datasets collected from the stocks of North Sea autumn spawners (ICES Divisions IVa, IVb, and IVc) and western Baltic spring spawners (ICES Subarea III). The size distributions obtained from the subordinator model largely match the observed size distributions, suggesting that this approach might be successfully implemented to support the assessment of commercial fish stocks, such as when modelling of size variability is required.

Connectivity effects on productivity, stability, and persistence in a herring metapopulation model

Secor, D. H., Kerr, L. A., Cadrin, S. X. — Mon, 17 Aug 2009 09:10:36 PDT

Secor, D. H., Kerr, L. A., and Cadrin, S. X. 2009. Connectivity effects on productivity, stability, and persistence in a herring metapopulation model. – ICES Journal of Marine Science, 66: 1726–1732.

Diverse and interacting spawning groups of Atlantic herring (Clupea harengus) have varying degrees of independence to environmental conditions. How these population components respond independently to the same set of environmental conditions, and are connected through straying or entrainment, will contribute to the aggregate metapopulation dynamics. The consequences of connectivity for productivity, stability, and persistence were evaluated in an age-structured model of a two-component metapopulation. Simulation scenarios of straying and entrainment were developed to examine the effects of component interchange and recruitment covariance on metapopulation attributes. Asynchronous component responses should result in reduced variance in metapopulation dynamics, which was measured as the portfolio effect (PE). Most types and magnitudes of connectivity reduced metapopulation productivity and stability. Increased connectivity tended to increase instability of a component by distributing the effect of strong year classes among components and disrupting the "storage effect" within components. Density-dependent straying and entrainment, respectively, showed stabilizing and destabilizing feedback cycles on metapopulation stability and persistence. Furthermore, high rates of connectivity tended to result in increased synchronous responses between components and depressed metapopulation productivity, stability, and PE. Exploitation on a metapopulation should similarly depress independence among components because high mortality will dampen component responses to environmental forcing.

Population integrity and connectivity in Northwest Atlantic herring: a review of assumptions and evidence

Stephenson, R. L., Melvin, G. D., Power, M. J. — Mon, 17 Aug 2009 09:10:36 PDT

Stephenson, R. L., Melvin, G. D., and Power, M. J. 2009. Population integrity and connectivity in Northwest Atlantic herring: a review of assumptions and evidence. – ICES Journal of Marine Science, 66: 1733–1739.

The issue of herring population structure has been debated for more than a century. Population integrity and connectivity have become an increasingly important problem for both resource evaluation (e.g. concern for the use of appropriate modelling approaches) and management (e.g. increasing attention to the preservation of within-species diversity and the complexity of mixed-stock fisheries). In recent decades, there has been considerable advancement in the scientific information related to herring population structure, but papers continue to demonstrate a spectrum of conclusions related to population integrity and connectivity at various scales. We review herring stock structure in the western Atlantic, specifically addressing the assumptions currently being used in management and the validity of scientific evidence on which these assumptions are based. Herring of the western Atlantic exhibit considerable population discreteness and limited connectivity on the temporal and spatial scales that are of relevance to management. Maintaining the resulting population complexity is a challenge, particularly because preservation of within-species diversity is an important element of an ecosystem approach to management.

Two components of Northeast Atlantic herring within the same school during spawning: support for the existence of a metapopulation?

Johannessen, A., Nottestad, L., Ferno, A., Langard, L., Skaret, G. — Mon, 17 Aug 2009 09:10:36 PDT

Johannessen, A., Nøttestad, L., Fernö, A., Langård, L., and Skaret, G. 2009. Two components of Northeast Atlantic herring within the same school during spawning: support for the existence of a metapopulation? – ICES Journal of Marine Science, 66: 1740–1748.

It has been hypothesized that some stocks of Atlantic herring are subject to genetic exchange and therefore should fit the definition of a metapopulation with subunits. Genetic exchange requires spatial overlap of individuals from different populations during spawning. We investigated a local herring population that is assumed to feed and spawn within the semi-enclosed marine ecosystem of Lindåspollene in west Norway, which is connected with the outer fjord only by a narrow sill. Acoustic recordings and gillnet samples demonstrated the mixed presence of two components within a single school throughout the spawning period 2005–2007. Members of the two components were of about the same size and in a similar stage of gonad development at all times, but the age composition was completely different. These observations represent the first documented case of different components being present in a spawning school and provide strong indications of regular interbreeding. Our data suggest that the two components represent autochthonous Lindås herring and allochthonous herring of coastal/oceanic origin, thereby supporting the metapopulation concept. Two alternative explanations, based on one migratory and one resident component of a single Lindås stock, are also discussed.

Temporal trends in stock origin and abundance of juvenile herring (Clupea harengus) in the Irish Sea

Burke, N., Brophy, D., Schon, P.-J., King, P. A. — Mon, 17 Aug 2009 09:10:36 PDT

Burke, N., Brophy, D., Schön, P-J., and King, P. A. 2009. Temporal trends in stock origin and abundance of juvenile herring (Clupea harengus) in the Irish Sea. – ICES Journal of Marine Science, 66: 1749–1753.

Celtic Sea herring (Clupea harengus) larvae partly disperse into the Irish Sea, where they mix with the resident stock during their first year of life. This affects the reliability of the use of acoustic estimates of juvenile abundance on the Irish Sea nursery grounds as a recruitment index for use in stock predictions. Otolith microstructure analysis can be used to distinguish between autumn-spawned and winter-spawned individuals. Because winter spawners do not occur in the Irish Sea, this component can be assigned to Celtic Sea immigrants. We used this method to estimate the proportion of winter-spawned individuals in samples of age-1 herring from the western Irish Sea over a 10-year period (1993–2003), and subtracted a corresponding proportion from the acoustic age-1 abundance estimates. The adjusted index for autumn-spawned (supposedly Irish Sea) juveniles was significantly correlated with the abundance of age-3 fish from the same year class in commercial catches and in the acoustic surveys (p < 0.05 and <0.01, respectively), whereas the correlations for unadjusted indices were not significant. These findings are discussed in relation to the monitoring and assessment of herring in the two areas.

Measuring and modelling Pacific herring spawning-site fidelity and dispersal using tag-recovery dispersal curves

Flostrand, L. A., Schweigert, J. F., Daniel, K. S., Cleary, J. S. — Mon, 17 Aug 2009 09:10:36 PDT

Flostrand, L. A., Schweigert, J. F., Daniel, K. S., and Cleary, J. S. 2009. Measuring and modelling Pacific herring spawning-site fidelity and dispersal using tag-recovery dispersal curves. – ICES Journal of Marine Science, 66: 1754–1761.

An approach of relating Pacific herring (Clupea pallasi) tag-recovery data to dispersal distances is presented. Observations from coded wire tag sampling (1999–2006) were used to represent adult herring interannual spawning patterns on the British Columbia coast. Six datasets were applied, differing by number of years-at-liberty (1, 2, or 3) and gear type of recapture (purse-seine or gillnet). In total, 227 tag-recovery samples, consisting of 5687 tag recoveries, were used. Distances were approximated to the shortest paths through water between the release and recapture sites. Recovery rate and distance relationships suggest that exponential models fit the data reasonably well, with average rates of change in recovery rates (slopes) varying from approximately –0.009 to –0.005. A combined slope estimate of –0.007 is similar to four of the six estimates. Using these models, the intensity of movement among five stock-assessment regions was estimated by applying distances relative to their centres. Fidelity estimates range from 53 to 90% across all models and regions, which is consistent with previous findings and premises that influence resource management. Interpretation and application of the modelling exercise are discussed in terms of previous and future work.

Variation in spatial distribution and migration of Icelandic summer-spawning herring

Oskarsson, G. J., Gudmundsdottir, A., Sigurdsson, T. — Mon, 17 Aug 2009 09:10:36 PDT

Óskarsson, G. J., Gudmundsdottir, A., and Sigurdsson, T. 2009. Variation in spatial distribution and migration of Icelandic summer-spawning herring. – ICES Journal of Marine Science, 66: 1762–1767.

The distribution of the fishable stock of Icelandic summer-spawning herring (Clupea harengus L.) and the overwintering grounds have changed with fishing seasons from 1978/1979 through 2006/2007. The possible causes investigated include variation in sea temperatures, stock size, and annual recruitment. The stock collapsed as a result of overfishing and environmental changes during the late 1960s, since when the spawning stock has gradually increased, from 11 kt in 1972 to 800 kt in 2006. These changes coincided with geographic variation in its distribution. We identify five phases, based on a graphic analysis and the centre of gravity of the fishery. Investigations on a large geographic scale gave no clear indication that sea temperature has affected the distribution. Changes were also not clearly related to stock size or year-class strength. The distribution change in the late 1990s may be partly explained by year classes adopting a new migration pattern when entering the fishable stock.

Regulating a complex adaptive system via its wasp-waist: grappling with ecosystem-based management of the New England herring fishery

Bakun, A., Babcock, E. A., Santora, C. — Mon, 17 Aug 2009 09:10:36 PDT

Bakun, A., Babcock, E. A., and Santora, C. 2009. Regulating a complex adaptive system via its wasp-waist: grappling with ecosystem-based management of the New England herring fishery. – ICES Journal of Marine Science, 66: 1768–1775.

We use the New England herring fishery as an example of the unresolved scientific issues pertinent to ecosystem-based management of forage-fish fisheries. The biomass of herring off New England is currently well above maximum sustainable yield (B_MSY), leading to pressure for expanded harvests. Associated concerns include: the maintenance of sufficiently abundant forage to meet the current needs of marine mammals and seabirds while supporting the rebuilding of overfished groundfish resources; the preservation of the service functions of a healthy population of pelagic zooplanktivorous fish to prevent possible outbreaks of pests, or hypoxia events; and the limitation of unintended bycatch of marine mammals, seabirds, and juvenile stages of groundfish. Perhaps a self-enhancing feedback loop, involving predation by herring on the early life stages of their groundfish predators, might result in regime shifts that could not be easily reversed. A plausible outcome of these ideas is a dichotomy in management choice between (i) promoting an ecosystem dominated by valuable groundfish resources and (ii) promoting the current ecosystem that features a large herring resource associated with abundant and energy-rich forage for marine mammals, seabirds, and continued high productivity of valuable shellfish resources.

Lumpers or splitters? Evaluating recovery and management plans for metapopulations of herring

Mon, 17 Aug 2009 09:10:36 PDT

Kell, L. T., Dickey-Collas, M., Hintzen, N. T., Nash, R. D. M., Pilling, G. M., and Roel, B. A. 2009. Lumpers or splitters? Evaluating recovery and management plans for metapopulations of herring. – ICES Journal of Marine Science, 66: 1776–1783.

The long-term management of a stock representing a metapopulation has been simulated in a case study loosely based upon herring to the west of the British isles, where stocks are currently assessed and managed by management area, although there is evidence of mixing between stocks (in terms of connectivity, migrations, and exploitation). The simulations evaluate scientific advice (based on virtual population analysis, VPA) and the sustainability of fishing under two population-structure scenarios, corresponding either to discrete stocks, which only mix on the feeding grounds, or where diffusion between stocks takes place. The ability of stock assessment to monitor stock status and exploitation levels was evaluated for defining stocks based on fishing areas and for stocks that combined fishing areas. The study showed that assessment based on VPA of the metapopulation could fail to detect overexploitation of stocks and fail to detect and distinguish between the effects of exploitation and regime shifts.

Oscillating reproductive strategies of herring in the western Atlantic in response to changing environmental conditions

Melvin, G. D., Stephenson, R. L., Power, M. J. — Mon, 17 Aug 2009 09:10:36 PDT

Melvin, G. D., Stephenson, R. L., and Power, M. J. 2009. Oscillating reproductive strategies of herring in the western Atlantic in response to changing environmental conditions. – ICES Journal of Marine Science, 66: 1784–1792.

Herring are broadly distributed in the western Atlantic, but reproductive activity is restricted to the central portion, from Cape Cod to northern Newfoundland. Spawning extends from early spring to late autumn. Two spawning types are recognized: spring spawners and autumn spawners. At the southern extreme, spawning occurs almost exclusively in autumn, whereas in the north, spring spawners prevail. Mid-range, both strategies are common, with spawning occurring throughout the entire season. We postulate that the temporal intra-stock dominance of spawning type is an adaptive reproductive strategy to changing environmental conditions. A conceptual model is presented to describe how reproductive success can oscillate between spawning strategies. In most years, environmental conditions appear to favour one type or the other, although strong year classes can co-occur when conditions are right. The recent change in environmental conditions, characterized by a general warming trend, favours autumn spawners and is consistent with our model. At the distributional extremes, stocks are restricted to a single spawning strategy, and broad-scale environmental changes can introduce large interannual variability and limit the reproductive and recovery potential of a stock. The dependence of a stock on a single spawning season may result in longer times to recover to target levels.

Objectives and harvest control rules in the management of the fishery of Norwegian spring-spawning herring

Tjelmeland, S., Rottingen, I. — Mon, 17 Aug 2009 09:10:36 PDT

Tjelmeland, S., and Røttingen, I. 2009. Objectives and harvest control rules in the management of the fishery of Norwegian spring-spawning herring. – ICES Journal of Marine Science, 66: 1793–1799.

The main element in the management of the Norwegian spring-spawning herring, as implemented by the coastal states, is to conduct the fishery based on a maximum fishing mortality (F) of 0.125. As the appropriateness of this rule (given the stated objectives) has not yet been tested thoroughly, we set out to do this by long-term simulations, in which we applied a range of alternative stock–recruitment relationships. These different relationships are estimated from historical replicates of the stock, as calculated by the herring-stock assessment model SeaStar. During prognostic simulations, a recruitment model is selected probabilistically for each historical replicate based on Akaike weights. We evaluate whether the management objectives are met by applying the present harvest control rule. Results are given for the current assessment option of natural mortality (M = 0.5) in the oldest aggregated age group and for the assessment option used in 2005 and earlier (M = 0.15). These show that perceptions of the long-term yield differ considerably and that the current management is somewhat on the conservative side from the perspective of maximum sustainable yield.

Temporal changes in maturation, mean length-at-age, and condition of spring-spawning Atlantic herring (Clupea harengus) in Newfoundland waters

Mon, 17 Aug 2009 09:10:36 PDT

Wheeler, J. P., Purchase, C. F., Macdonald, P. D. M., Fill, R., Jacks, L., Wang, H., and Ye, C. 2009. Temporal changes in maturation, mean length-at-age, and condition of spring-spawning Atlantic herring (Clupea harengus) in Newfoundland waters. – ICES Journal of Marine Science, 66: 1800–1807.

We investigated temporal trends in some life-history traits of Atlantic herring. Population size of Newfoundland herring stock complexes declined precipitously through the 1970s. Maturation age and size also decreased substantially, but not until the late 1980s. Although significant effects were found for region and gear type, these were only minor compared with the general trend. No effects were found for sex. Changes in maturation age and size can represent an evolutionary response to fishery-induced selection, or phenotypic plasticity as a result of a compensatory response to stock declines, or a response to other changes in the environment. Length-at-age and body condition decreased concurrently with changes in maturation, suggesting that declines in maturation age and size were not a compensatory response to reduced stock sizes. This supports the hypothesis of evolutionary changes in maturation. However, increases observed in the most recent year classes, and concurrent changes in other species, suggest that changes in the environment may have also affected age- and size-at-maturation.

A two-stage biomass model for Irish Sea herring allowing for additional variance in the recruitment index caused by mixing of stocks

Roel, B. A., De Oliveira, J. A. A., Beggs, S. — Mon, 17 Aug 2009 09:10:36 PDT

Roel, B. A., De Oliveira, J. A. A., and Beggs, S. 2009. A two-stage biomass model for Irish Sea herring allowing for additional variance in the recruitment index caused by mixing of stocks. – ICES Journal of Marine Science, 66: 1808–1813.

An assessment of Irish Sea (ICES Division VIIa, North) herring using a two-stage biomass model was undertaken given lack of internal consistency in the survey age-disaggregated index. The model constrains recruitment variability and reduces the number of catchability parameters to address concerns of overparameterization. An extra parameter was incorporated to estimate the component of the variance resulting from the mixing of Celtic Sea and Irish Sea juvenile herring in the survey area. This additional variance, although imprecise, represented a large part of the total variance associated with the recruit survey data. More information on the variability of Irish Sea herring recruitment is required to estimate additional variance in the context of the two-stage biomass model presented. Limitations in the age-composition data and potential interannual variation in the selection pattern of the fishery favour an assessment method, such as the two-stage biomass method, which is based on a simplified age structure and does not require separability assumptions.

Evaluation of the quality of the North Sea herring assessment

Simmonds, E. J. — Mon, 17 Aug 2009 09:10:36 PDT

Simmonds, E. J. 2009. Evaluation of the quality of the North Sea herring assessment. – ICES Journal of Marine Science, 66: 1814–1822.

The assessment of North Sea herring has been used to give advice on catch quota for more than 20 years. The data sources comprise acoustic surveys, International Bottom Trawl Surveys, Methot Isaacs–Kidd net post-larval surveys, larval surveys, and catch-at-age data. These sources and their uses are briefly reviewed, and the changes in the weighting attached to each index in the assessment over time are discussed. The performance of the assessment is examined both in historical and analytical retrospectives of spawning–stock biomass and fishing mortality, and in retrospective assessments of numbers by cohort. Increased length of the time-series, the use of a statistical model with appropriate weighting, and a more consistent management strategy have all contributed to the assessment becoming highly stable from one year to the next. The results presented lead to the conclusion that the assessments provide an excellent basis for the management of this stock.

List of reviewers

Mon, 17 Aug 2009 09:10:37 PDT