ICES Journal of Marine Science - current issue

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.