ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on February 6, 2007
ICES Journal of Marine Science: Journal du Conseil 2007 64(3):503-511; doi:10.1093/icesjms/fsl047
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Integrated fisheries assessment and possible causes for the collapse of anchovy kilka in the Caspian Sea
1 Cefas Lowestoft Laboratory, Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK
2 Institute of Zoology of the National Academy of Sciences Azerbaijan, passage 1128, Quarter 504, Baku 370073, Azerbaijan
Correspondence to G. M. Daskalov: tel: +44 1502 524584; fax: +44 1502 524511; e-mail: georgi.daskalov{at}cefas.co.uk
Daskalov, G. M., and Mamedov, E. V. 2007. Integrated fisheries assessment and possible causes for the collapse of anchovy kilka in the Caspian Sea. – ICES Journal of Marine Science, 64: 503–511.Anchovy kilka (Clupeonella engrauliformis) is the most abundant species of fish in the Caspian Sea. An integrated catch-at-age analysis based on commercial catch data and relative abundance indices from research surveys over the period 1991–2004 indicated two main periods. First, a period of high catches, from 1991 to 2000, sustained by relatively good recruitment and high spawning-stock biomass. At the end of this period, catches peaked at up to 271 400 t, fishing mortality reached 1.8 y–1 in 1999, and overfishing seems to have taken place. Over the next period, 2001–2004, the stock virtually collapsed, recruitment failing in 2001 and remaining very low thereafter. In 2005, total catches dropped to a historical minimum of 54 300 t. The most likely primary cause of the stock collapse is the invasion and spread of the ctenophore Mnemiopsis leidyi in the Caspian Sea. The dramatic recruitment failure from 2001 to 2004 is primarily attributed to competition/predation by this ctenophore, although other factors, including overfishing, likely contributed.
Keywords: age-structured stock assessment, anchovy kilka, Caspian Sea, ecosystem effects, fish stock collapse, invasive species, Mnemiopsis leidyi, overfishing
Received 26 April 2006; accepted 22 December 2006; advance access publication 6 February 2007.
 |
Introduction |
|---|
 Top Introduction Data and methodsResultsDiscussionThe futureReferences |
|---|
Three species of kilka (Clupeonella spp.) are important commercially in the Caspian Sea, together accounting in the past decade for > 80 % of the total catch, as well as being a crucial part of the food chain. Their sustainable management is therefore vital to future fisheries operations and the health of the Caspian Basin ecosystem. The Caspian environment has, however, altered significantly during the past 30 y. Apart from natural changes attributable largely to variability in the sea level (Rodionov, 1994), major anthropogenic impacts on the system include pollution by domestic and industrial waste, development of oil and gas fields, and inefficiently regulated fishing (Salmanov, 1999; Ivanov, 2000).
Anchovy kilka (Clupeonella engrauliformis) is distributed in the central and southern Caspian Sea, with main concentrations in surface waters above the shelf break (Lovetskaya, 1951; Paritskiy, 1989). During summer, the species stays above the seasonal thermocline where dense patches of its zooplankton prey are located. The main food of anchovy kilka is copepods, particularly Eurytemora grimmi (70%) (Lovetskaya, 1951; Prikhodko and Skobelina, 1967; Tinenkova and Pochitaeva, 1985). Peak spawning takes place in the southeastern Caspian in October and November, where warmer water and abundant food during winter and spring favour larval growth and survival (Prikhodko, 1979; Sedov and Paritskiy, 2001). Kilka is a major food item for piscivores in the Caspian Sea, which include sturgeon (Acipenser spp. and Huso huso) and seals (Phoca caspica). According to Prikhodko (1975), the annual consumption of anchovy kilka by sturgeon and seals during the 1960s and early 1970s was some 400 000 t.
Anchovy kilka is fished during the whole year, less intensively in summer, mainly in the central (
40% of the catch) and southern (60% of the catch) Caspian Sea. The commercial size for anchovy kilka is 7 cm. Large catches of anchovy kilka were made during the 1970s and 1980s using light-fishing with cone nets and fish pumps (up to 400 000 t annually), but from 1990, catches decreased to about half that level; since 2000, the stock has virtually collapsed commercially, catches falling below 100 000 t y–1 (Figure 1). Recently too, the efficiency of the fisheries (as assessed in terms of catch per unit effort, cpue) has also dropped (Mamedov, 2006). The catch per day has decreased more dramatically for industrial fishing vessels using fish pumps which need larger fish schools than for those using cone nets. Smaller vessels have proved to be more efficient, and such vessels have dominated the fishery in the past few years.
|
A major stress factor for the Caspian Sea pelagic ecosystem in the past decade has been the invasion of the ctenophore (comb jelly) Mnemiopsis leidyi (Kasymov, 2001). In 2001, the total allowable catch for anchovy kilka was 300 000 t, but just 58 800 t were caught. By 2005, catches had declined even further to just 54 300 t, the lowest on record since the stock was fully exploited in the 1970s and 1980s. Since 2001, recruitment has been very poor, and significant changes in population size/age structure, somatic growth, and condition have been reported (Kostyurin et al., 2005; Mamedov, 2006).
The aim of this article is to assess the anchovy kilka stock in the Caspian Sea, using an integrated age-structured model incorporating information on fisheries catches and from research surveys and to provide some of the information needed to support management. The study also aims to serve as a pilot project demonstrating the use of state-of-the-art methodology that could in future be applied to other valuable resources of the Caspian, e.g. sturgeon, kutum (Rutillus frisii kutum), and herring (Alosa spp.).
|
Data and methods |
|---|
|
TopIntroductionData and methodsResultsDiscussionThe futureReferences |
|---|
Input data for the stock assessment of anchovy kilka in the Caspian are numbers-at-age in the catch and individual weight-at-age in the stock (Table 1), natural mortality (assumed constant for all years and ages, M = 0.54 y–1) (Mamedov, 2006), and relative abundance-at-age from research surveys (Table 2). Commercial catch and survey data were taken from the sources listed in Table 3. M was estimated by the method proposed by Pauly (1980; Mamedov, 2006). The estimated value of 0.54 falls between the values found for the other two species of kilka in the Caspian, namely 0.48 and 1.04 for common (Clupeonella cultriventris caspia) and big-eye kilka (Clupeonella grimmi), respectively (Mamedov, 2006), but it is similar to values for related species reported by Prodanov et al. (1997).
|
|
|
The size and the age composition of the exploited stock, the relative abundance-at-age of the stock, and the recruitment strength have been determined according to methodology developed in the Caspian Scientific Research Institute of Fisheries (KaspNIRKh) by Prikhodko (1967; Sedov et al. 1998; Mamedov, 2006). Research surveys were carried out in areas where the anchovy kilka stock was concentrated and commercial fishing boats were operating with cone nets. Kilka research catches (using a commercial fishing vessel) were made at night in the traditional commercial manner, using a cone net with a 1500 kW light to attract the fish. The relative abundance of the adult stock (i.e. catch of the cone net per standard unit of effort, i.e. 0.5 h fishing) is assessed during summer (July) and autumn (October) surveys, and recruitment strength is estimated as the relative abundance of young-of-the-year fish (9–10 months old in summer) in the surface waters of the central and southern Caspian, where they are commonly distributed.
We consider the assembled input data to be representative of the entire anchovy kilka stock in the central and southern Caspian Sea. The analysis is based on the best information available to the authors (published papers and data collected as part of EVM's PhD project), but it should be regarded as a pilot study that could be the starting point for future regional and/or international working groups.
We used integrated catch-at-age analysis (ICA) (Patterson and Melvin, 1996) to perform the regional stock assessment of anchovy kilka in the Caspian Sea. ICA is a statistical catch-at-age method based on the Fournier and Deriso models (Deriso et al., 1985). It applies a statistical optimization procedure to calculate population numbers and fishing mortality coefficients-at-age from catch numbers-at-age, natural mortality, and survey indices. The dynamics of a cohort (generation) in the stock are expressed by two non-linear equations, referred to as the survival equation (exponential decay) and the catch equation:
|
|
For parameter estimation, the ICA algorithm minimizes the weighted sum of squared residuals of observed and modelled catch and relative abundance indices (cpue), assuming log-normal distributions for catches and survey indices:
|
|
, I, and Î are observed and estimated catches and age-structured indices, respectively, and a, y, and f are subscripts for age, year, and fleet. Weighting factors pc and pi, associated with catches and different survey indices, respectively, are ideally set equal to their inverse variances and can be calculated on the basis of the residuals between modelled and observed values. However, in practice, weighting factors are set by the user on the basis of information about the reliability of different indices and current experience with modelling the stock. The observation equation for survey indices is
|
|
In our analyses and discussion, we refer to additional published information on the biotic environment (Table 1) and to results of studies of age, size, growth, and life history of anchovy kilka presented in Mamedov (2006).
|
Results |
|---|
|
TopIntroductionData and methodsResultsDiscussionThe futureReferences |
|---|
The separable model was constrained to the last 5 y of data (2000–2004), assuming a constant selection pattern (Figure 2). Equal weighting factors (equal to 1) were assigned to all catches in the separable model. The relationships between both age-structured and young fish indices were fitted by linear functions, and all survey indices and ages were equally weighted in estimating the total sum of squared residuals. The optimization of the partial (separable and catchability models) and the total sum of squared residuals generated pronounced and consistent minima. Examination of the residuals and model statistics did not reveal important deviations from model assumptions. The results showed good agreement with the research survey data (Figure 3). The main results in terms of population estimates, fishing mortality, recruitment, and spawning-stock biomass (SSB) are presented in Figures 3 and 4. The population has changed dramatically since the mid-1990s. Two main periods can be distinguished in both stock and fishery: first, a period of high catches, from 1991 to 2000, sustained by relatively good recruitment and SSB. At the end of this period, catches peaked at up to 271 400 t, and fishing mortality reached 1.8 y–1 in 1999. Mean fishing mortality increased to 1.8 in 1999. As a result of the heavy fishing and reduction in growth (Table 1) (Kostyurin et al., 2005; Mamedov, 2006), the stock showed clear signs of overfishing. Then, between 2001 and 2004, the stock virtually collapsed. Recruitment failed dramatically in 2001, and SSB quickly declined. Catches dropped to just 54 300 t in 2005, the lowest on record since the stock was fully exploited in the 1970s and 1980s.
|
|
|
|
Discussion |
|---|
|
TopIntroductionData and methodsResultsDiscussionThe futureReferences |
|---|
Application of ICA to anchovy kilka assessment is appropriate because (i) it is an advanced statistical method based on clear assumptions about data and error distributions; (ii) it is an internationally recognized approach that has been used successfully on other stocks; (iii) it allows integration of various sources of information from, for instance, commercial fisheries and research surveys; (iv) it is relatively robust to noisy data; (v) it works well with short-lived species.
The main features of the time-series of abundance and fishing mortality produced by ICA are the increase in fishing mortality between 1996 and 2000 and the immediate sharp drop in abundance and subsequently catch (Figure 4). The collapse of a fishery has been defined as a sustained period of very low catches following sudden decline after a period of high catches (Cooke, 1984; Mullon et al. 2005). Evaluating all evidence about the recent decline of anchovy kilka and the fact that catches in the last 5 y of the time-series dropped by about five times from the average for the period of the developed fisheries (1965–1990), we define here the recent sudden decline of anchovy kilka as a fisheries collapse (Figure 1).
The main cause of the collapse would seem to be recruitment failure. Reduced recruitment subsequently led to decreases in exploitable biomass and SSB (Figures 3 and 4). The increase in fishing mortality in 1999 and 2000, corresponding to large catches, indicates that the stock then might have been seriously overfished. However, the stock may actually have been chronically overfished at a lesser exploitation rate since 1993, when catches first decreased to levels well below historical averages (Figure 1). Patterson (1992) recommended a global reference point for precautionary management of small pelagic fish at an exploitation rate (F/Z) of 0.4. Given that natural mortality (M) was 0.54, the corresponding fishing mortality at precautionary level (Fpa) would be 0.36, which seems a reasonable (though conservative) value for a small pelagic fish species such as anchovy kilka. The results here show that F considerably exceeded 0.36 in the period 1998–2000 (Figure 4b).
The most likely negative biotic influence on anchovy kilka recruitment is the invasion of the Caspian Sea by the comb jelly M. leidyi (Figure 5). M. leidyi was first recorded in the Caspian Sea in November 1999 by KaspNIRKh scientists conducting an underwater video survey near the border between Kazakhstan and Turkmenistan (Ivanov et al., 2000). By spring 2001, M. leidyi had become the dominant species in the pelagic ecosystem and extended throughout the whole Caspian Sea. Anchovy kilka fecundity studied on the basis of samples taken from research survey hauls varied from 8510 to 58 340 mature oocytes per fish (35 876 on average) (Mamedov, 2004), so the recruitment failure cannot be ascribed to a decrease in egg production. Further, during the research survey of summer 2003, large numbers of anchovy kilka larvae were found off Azerbaijan, raising hopes of a stock recovery. Unfortunately, the 2004 survey caught very few juvenile anchovy kilka, so a high level of post-larval mortality attributed to competition with or predation by M. leidyi (a voracious zooplankton predator) is assumed. Fish larvae <4 mm are especially susceptible to starvation (Tkach et al., 1998). In 2000, the zooplankton biomass dropped four to ten times compared with the situation in 1998 (Figure 6) (Polyaninova et al., 2001): the copepod biomass reduced by a factor of 4–5, cladocerans by a factor of 6–122, and rotifers by a factor of 5–20. In August 2000, the stock of the important prey species E. grimmi dropped to about one-eighth of its previous level in the central Caspian, and it was not found in the southern Caspian (Tinenkova and Petrenko, 2003). The distribution of spawning anchovy kilka in summer overlaps with current maxima of the M. leidyi population. Efforts have been made to investigate how predatory or competitive interaction with M. leidyi negatively impacts kilka species (Kasymov, 2001; Vostokov et al., 2002; Kuliyev, 2004; Sokolskiy and Kamakin, 2004). M. leidyi density is higher in the central areas of the southern Caspian than in the coastal areas of Azerbaijan (Vostokov et al., 2002). Further, unusually high densities (1600 m–2) of M. leidyi (mainly juveniles <5 mm) have been found in the pelagic zone over a water depth of 700–800 m associated with an algal bloom. In July and August, 90% of the M. leidyi are <15 mm (M. leidyi can attain 61–65 mm) (Kuliyev, 2004). This means that, under favourable conditions, the M. leidyi population can bloom and locally impact zooplankton and fish larvae if they overlap spatially. M. leidyi had a similar devastating impact on the ecosystem of the Black and Azov Seas (Volovik, 2000). M. leidyi blooms may be responsible for entire foodweb changes through trophic cascades leading to algal blooms and water quality deterioration (Kideys et al., 2005), as in the Black Sea (Daskalov, 2002; Daskalov et al., in press).
|
|
In order to limit further damage by M. leidyi to the Caspian ecosystem, it has been proposed to introduce another ctenophore, Beroe ovata, a natural predator of M. leidyi. B. ovata "naturally" followed M. leidyi (most likely in ballast water) into the Black Sea, and at present there is some evidence that it may negatively impact M. leidyi abundance (Shushkina et al., 2000). However, evidence of large-scale population control of M. leidyi by B. ovata is lacking (EUROGEL, 2006). Natural predators of M. leidyi already exist in the Caspian Sea. Analyses of the stomach contents of three species of goby (Gobius fluviatilis pallas, Neogobius melanostomus, and Neogobius kessleri gorlap) have shown that they consume M. leidyi, perhaps up to 7–9% of their diet. Preliminary calculations have shown that gobies in the northwestern and southeastern Caspian can consume 15 600 t of ctenophores in summer, i.e. 10–15% of the total M. leidyi biomass there (Stepanova and Sokolskiy, 2003). Overall, though, most interested parties are cautious about taking the option of introducing another exotic species to the Caspian to "control" M. leidyi.
Apart from M. leidyi, environmental conditions such as sea level and freshwater run-off are believed to influence anchovy kilka stock dynamics (Sedov et al., 1998). Recently (2000–2004), hydrological conditions have likely negatively impacted the distribution of exploitable concentrations of anchovy kilka: strong thermal stratification and poor vertical mixing have created unfavourable conditions for the fish. The temperature of the upper layers has reached 26–27°C, and as a consequence, anchovy kilka migrated deeper, into the cooler, deeper layers of the sea.
In April and May 2001, a mass mortality of 166 000 t of kilka (mainly anchovy kilka) was recorded (Sedov et al. 2002b) in the central and southern Caspian Sea. Earthquake data reveal that, in the first quarter of 2001, the local Absheron seismic plate was active, and water and gas systems in the soil were unstable and indicative of hydro-volcanic events or significant gas blow-outs containing poisonous substances, which most probably contributed to the mass kill (Katunin et al., 2002).
In summary, therefore, and as generally happens to fish stocks, several factors may have influenced anchovy kilka dynamics negatively during the past decade, excessive fishing, climate change, seismic activity, and invasion by the exotic M. leidyi being the most obvious. Such natural and anthropogenic factors usually interact and ultimately sometimes lead to overfishing and stock collapse. Overfishing happens when there is a decline in fish stock abundance, perhaps caused by weak recruitment attributable to climate change or starvation/predation of fish larvae. Diminished abundance and depressed somatic growth (Mamedov, 2006) led to a low exploitable stock biomass, usually in the succeeding 1 or 2 y, and in short-lived species, fish 1 and/or 2 y old dominate stock biomass. A depressed biomass is then confronted with conservative or increased fishing effort because of the inability of fishery management and industry to forecast and to adapt to changes in a fish stock. High fishing pressure applied on a low stock biomass leads to excessive fishing mortality even if the catch is relatively small, because the catch is taken from a less abundant stock. The result is then either a collapse of the adult stock (the first phase of overfishing or growth-overfishing) (Sissenwine and Shepherd, 1987; Cushing, 1995) or even recruitment-overfishing, i.e. directly harvesting immature fish or indirectly affecting the reproductive potential by reducing the quantity and the quality of the reproductive output through effects on the spawning stock (the second phase of overfishing) (Sissenwine and Shepherd, 1987; Cushing, 1995).
Cyclic fluctuations in fish abundance can be related to climate change (e.g. sea-level fluctuations, freshwater run-off) (Rodionov, 1994; Sedov et al., 1998, Daskalov, 2003). The increased commercial catch of anchovy kilka after 2000 followed the drop in SSB in 1999 and 2000 and led to a very high fishing mortality (Figure 4b). Further, the stock has been additionally subject to mass mortality following the seismic events in 2001 (Sedov et al., 2002b). The stock would likely have been negatively affected, and its low biomass and slower somatic growth in 1999–2001 (Kostyurin et al., 2005) could have indirectly favoured expansion of the M. leidyi population (Figure 5). The mechanism of such an effect could be that a decrease in fish biomass and hence in consumption of zooplankton by anchovy kilka could have locally provided surplus unutilized zooplankton production to be used by the burgeoning M. leidyi stock (the ctenophores are particularly efficient when food density is high) (Sørnes and Aksnes, 2004). Such a hypothetical mechanism of the onset of M. leidyi blooms has been described for the Black Sea by Daskalov et al. (in press). Although total zooplankton biomass in 2000 was low (Figure 6), the hypothetical effect may still have taken place locally months and/or years earlier.
|
The future |
|---|
|
TopIntroductionData and methodsResultsDiscussionThe futureReferences |
|---|
In the past few years, anchovy kilka have been under severe stress from the combined competitive pressures of M. leidyi, environmentally induced mass mortality (the 2001 event), and an increasing demand from fisheries following a shortage of fish in the Caspian Sea, conceivably driving it to collapse. According to Bagheri et al. (2004), the decline in anchovy kilka catches off Iran during the period 1998–2001 caused economic losses of at least US$15 million. The present study clearly indicates that anchovy kilka have recently been overfished and consequently, likely because of the catastrophic invasion by M. leidyi, have virtually collapsed. Under such circumstances, the obvious goal for management in the next few years would be to rebuild the stock. To achieve such a management objective, greatly restricted fishing or perhaps even a few years' moratorium on fishing is needed. Experience in the Black Sea has shown that the decreased sprat (Sprattus sprattus) and anchovy (Engraulis encrasicolus) stocks quickly recovered even with M. leidyi present after fishing was reduced (Daskalov et al., in press).
Because of the importance of anchovy kilka in the whole Caspian ecosystem and its importance as a fishery, coordinated international effort is urgently needed. In our opinion, this should include developing state-of-the-art stock assessment using, inter alia, integrated approaches incorporating information from fisheries and research surveys (if feasible, also including hydroacoustic estimates of biomass). Long time-series of abundance and mortality estimates are required, leading to the establishment of biological limits (reference points and directions) for sustainable harvesting and preservation of the ecosystem. Further studies that would be helpful for an ecosystem-orientated management regime would be to identify the main natural (sea level, river inflow, climate) and anthropogenic (overfishing, M. leidyi, pollution) factors that influence the stock dynamics. Given the present status of anchovy kilka, immediate management and regulatory actions should be considered and, if feasible, implemented (as recommended by FAO, 1996).
|
Acknowledgements |
|---|
The authors are grateful to Andrew Payne for reading and improving the English of the draft manuscript and providing pertinent comments, Mikhail Bondarenko for providing landings data, Jose de Oliveira for technical advice, and editor Verena Trenkel and three anonymous reviewers for providing comments and constructive criticism. We acknowledge the SMCFP (EU–TACIS) project for supporting the study financially.
|
References |
|---|
|
TopIntroductionData and methodsResultsDiscussionThe futureReferences |
|---|
-
Bagheri S., Kideys A., Sabkara D., Anzali B. (2004) Studying Ctenophora (Mnemiopsis leidyi) at the Iranian seashore of the Caspian Sea. Material of the First International Scientific and Practical Conference of Young Scientists "Complex Research of the Biological Resources of the South Seas and Rivers",, Astrakhan pp. 28–31 July 2004. 244 pp.
Cooke J. G. (1984) Glossary of technical terms. In May R. M. (Ed.). Exploitation of Marine Communities(Springer, New York) pp. 341–341 348 pp.
Cushing D. H. (1995) Population Production and Regulation in the Sea: a Fisheries Perspective. (Cambridge University Press, Cambridge, UK) 344 pp.
Daskalov G. M. (2002) Overfishing drives a trophic cascade in the Black Sea. 225: pp. 53–63 Marine Ecology Progress Series.
Daskalov G. M. (2003) Long-term changes in fish abundance and environmental indices in the Black Sea. 255: pp. 259–270 Marine Ecology Progress Series.
Daskalov G. M., Prodanov K., Zengin M. The Black Sea fisheries and ecosystem change: discriminating between natural variability and human-related effects. AFS Books (in press).
Deriso R. B., Quinn T. J., Neal P. R. (1985) Catch-age analysis with auxiliary information. Canadian Journal of Fisheries and Aquatic Sciences 42: pp. 815–824.
Epshteyn B. M. and Abdullaeva N. M. (1985) Zooplankton of southern Caspian. The Caspian Sea: Fauna and Biological Productivity(Nauka, Moscow) pp. 103–108 277 pp. (in Russian).
EUROGEL. (2006) EUROpean GELatinous zooplankton: mechanisms behind jellyfish blooms and their ecological and socio-economic effects. EC Framework 5, Contract EVK3–CT–2002–00074, Project Final Report (30/01/2006)52 pp.
FAO. (6–13, 1996) Precautionary approach to capture fisheries and species introductions. Elaborated by the Technical Consultation on the Precautionary Approach to Capture Fisheries (including species introductions). (FAO Technical Guidelines for Responsible Fisheries, Lysekil, Sweden) 2: pp. 54 June 1995.
Ivanov V. P. (2000) Biological Resources of the Caspian Sea. , Astrakhan pp. 96 KaspNIRKh.
Ivanov V. P. (2001) The basic ways of conservation and use of biological resources of the Caspian Sea. The State of the Commercial Objects Stocks in the Caspian and their Use(KaspNIRKh Publishing, Astrakhan) pp. 8–24.
Ivanov V. P., Kamakin A. M., Ushivtzev V. B., Shiganova T. A., Zhukova O., Aladin N., Wilson S. I., et al. (2000) Invasion of the Caspian Sea by the comb jellyfish M. leidyi leidyi (Ctenophora). Biological Invasions 2:255–258.[CrossRef]
Kasymov A. G. (2001) New introduced species in the Caspian Sea—Mnemiopsis leidyi (A. Agassiz). The Invasion of the Caspian Sea by the Comb Jelly Mnemiopsis—Problems, Perspectives, Need for Action, Baku, Azerbaijan pp. 5 www.caspianenvironment.orgApril 2001.
Katunin D. N., Golubov B. N., Kashin D. V. (2002) The impulse of hydrovulkanism on the Derbent Hollow in the central Caspian as a possible factor in the large-scale mortality of anchovy and big-eye kilka in spring 2001. Fisheries Researches in the Caspian. Scientific Research Works Results for 2001(KaspNIRKh Publishers, Astrakhan) pp. 41–55 630 pp.
Kideys A. E., Soydemir N., Eker E., Vladimirov V., Soloviev D., Melin M. (2005) Phytoplankton distribution in the Caspian Sea during March 2001. Hydrobiologia 543:159–168.[CrossRef][Web of Science]
Kostyurin N. N., Sedov S. I., Zykov L. A., Paritskiy Yu. A., Andrianova S. B., Aseinova A. A., Kolosyuk G. G., et al. (2005) The present state of stocks and the fishery of Caspian marine species. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2004(KaspNIRKh Publishing, Astrakhan) pp. 378–402 616 pp. (in Russian).
Kuliyev Z. M. (2004) Dynamics of Mnemiopsis distribution in the Azerbaijan sector of the Caspian Sea in 2001–2002. In Dumont H., Shiganova T. A., Niermann U. (Eds.). Aquatic Invasions in the Black, Caspian and Mediterranean Seas. The Ctenophores Mnemiopsis leidyi and Beroe in the Ponto-Caspian and other Aquatic Invasions(Kluwer, Dordrecht) pp. 203–204 313 pp.
Lovetskaya A. A. (1951) Caspian kilka and their fishery. (Food Industry, Moscow) pp. 45 (in Russian).
Mamedov E. V. (2004) Morphobiological peculiarities of kilka along the Azerbaijan coast of Caspian Sea in the modern ecological conditions. PhD dissertation. Institute of Zoology, Academy of Sciences of Azerbaijan pp. 166 (in Russian).
Mamedov E. V. (2006) The biology and abundance of kilka (Clupeonella spp.) along the coast of Azerbaijan, Caspian Sea. ICES Journal of Marine Science 63:1665–1673.
Mullon C., Fréon P., Cury P. (2005) The dynamics of collapse in world fisheries. Fish and Fisheries 6:111–120.[CrossRef][Web of Science]
Paritskiy Yu. A. (1989) The anchovy kilka. In Belyaeva V. N. and Kazancheev Ye. N. (Eds.). Caspian Sea: Ichthyofauna and Commercial Resources(Nauka, Moscow) pp. 83–94 236 pp. (in Russian).
Patterson K. (1992) Fisheries for small pelagic species: an empirical approach to management targets. Reviews in Fish Biology and Fisheries 2:321–338.[CrossRef][Web of Science]
Patterson K. R. and Melvin G. D. (1996) Integrated Catch-at-Age Analysis, version 1.2. Scottish Fisheries Research Report 58:62.
Pauly D. (1980) On the interrelationships between natural mortality, growth parameters and mean environmental temperature in 175 fish stocks. Journal du Conseil International pour l'Exploration de la Mer 39:175–192.
Polyaninova A. A., Ardabieva A. G., Tatarintzeva T. A., Terletzkaya O. V., Tarasova L. I., Tinenkova D. Kh., Petrenko E. L., et al. (2001) The hydrobiological characteristic of the commercial fish fattening conditions in the Caspian Sea. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2000(KaspNIRKh Publishing, Astrakhan) pp. 110–125 512 pp. (in Russian).
Pope J. G. and Shepherd J. G. (1982) A simple method for consistent interpretation of catch-at-age data. Journal du Conseil International pour l'Exploration de la Mer 40:176–184.
Prikhodko B. I. (1967) The methods of stock assessment of the anchovy kilka Clupeonella enrauliformis, their fluctuations and causes affecting the rejuvenation of the fishing stock in recent years. Proceedings of Stock Assessment and Prediction of CatchesTrudy VNIRO 57: pp. 219–230 (in Russian).
Prikhodko B. I. (1975) Kilka of the Caspian Sea and their abundance. Trudy VNIRO 108:144–153 (in Russian).
Prikhodko B. I. (1979) About a relation between the harvest of juveniles of the Caspian anchovy kilka Clupeonella engrauliformis (Borodin) and temperature of water. Journal of Ichthyology 19:291–301 (in Russian).
Prikhodko B. I. and Skobelina R. S. (1967) The feeding of the Caspian kilka. Trudy KaspNIRKh 23:111–136 (in Russian).
Prodanov K., Mikhailov K., Daskalov G., Chashchin A., Arkhipov A., Shlyakhov V., Ozdamar E. (1997) Environmental management of fish resources in the Black Sea and their rational exploitation. Studies and Reviews. (General Fisheries Council for the Mediterranean. FAO, Rome)62.
Rodionov S. N. (1994) Global and Regional Climate Interaction: the Caspian Sea Experience. Water Science and Technology Library, 11(Kluwer, Dordrecht) pp. 233.
Salmanov M. A. (1999) Ecology and Biological Productivity of the Caspian Sea. (Chevron Overseas Petroleum, Baku) pp. 397.
Sedov S. I., Aseynova A. A., Paritskiy Yu. A. (1998) Kilka. In Belyaeva V. N., Ivanov V. P., Zilanov V. K. (Eds.). Scientific Bases for Sustainable Fisheries and Regional Distribution of Commercial Objects of the Caspian Sea(VNIRO Publishing, Moscow) pp. 167 pp. 83–89 (in Russian).
Sedov S. I. and Paritskiy Yu. A. (2001) Biology and fisheries of marine fish. The State of Commercial Objects Stocks in the Caspian and their Use(KaspNIRKH Publishing, Astrakhan) pp. 409 pp. 186–205 (in Russian).
Sedov S. I., Paritskiy Yu. A., Kolosyuk G. G. (2002a) Kilka stock state in the middle and southern Caspian and forecast of their harvest for 2003. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2001(KaspNIRKh Publishing, Astrakhan) pp. 630 pp. 336–340 (in Russian).
Sedov S. I., Paritskiy Yu. A., Kolosyuk G. G., Kanatiev S. V. (2002b) On kilka mortality in the middle and southern Caspian in 2001. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2001(KaspNIRKH Publishing, Astrakhan) pp. 630 pp. 340–345 (in Russian).
Sedov S. I., Paritskiy Yu. A., Zikov L. A., Kolosyuk G. G., Aseynova A. A., Andrianova S. B., Kanatiev S. V., et al. (2004) The states of stocks of Caspian marine fish and prospects for their commercial utilization. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2003(KaspNIRKH Publishing, Astrakhan) pp. 360–368 570 pp. (in Russian).
Shushkina E. A., Musaeva E. I., Anokhina L. L., Lukasheva T. A. (2000) The role of gelatinous macroplankton, jellyfish Aurelia, and ctenophores Mnemiopsis and Beroe in the planktonic communities of the Black Sea. , Moscow 40: pp. 809–816 Oceanology (in Russian).
Sissenwine M. P. and Shepherd J. G. (1987) An alternative perspective on recruitment overfishing and biological reference points. Canadian Journal of Fisheries and Aquatic Sciences 44:913–918.
Sokolskiy A. F. and Kamakin A. M. (2004) The spread of the ctenophore Mnemiopsis in the Caspian Sea in 2003 and its impact on the environment. Fisheries Researches in the Caspian. Scientific-Research Works Results for 2003(KaspNIRKH Publishing, Astrakhan) pp. 183–190 570 pp. (in Russian).
Sokolskiy A. F., Shiganova T. A., Zikov L. A. (2001) The biological pollution of the Caspian Sea by the comb jelly Mnemiopsis and the first results of its impact on the pelagic system. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2000(KaspNIRKh Publishing, Astrakhan) pp. 105–110 512 pp.(in Russian).
Sørnes T. A. and Aksnes D. L. (2004) Predation efficiency in visual and tactile predators. Limnology and Oceanography 49:69–75.[Web of Science]
Stepanova T. G. and Sokolskiy A. F. (2003) Natural enemies of the ctenophore Mnemiopsis leidyi in the Caspian Sea. Proceedings of the International Conference Fisheries Science in the Caspian Sea: Tasks and ProspectsJuly 2003Makhachkala(KaspNIRKh Publishing, Astrakhan) pp. 560 pp. 145–147 (in Russian).
Tarasov A. G. (2001) The invasion of Mnemiopsis into the Caspian: main results for 2001. The Bulletin of the Caspian Sea 5:120–126 (in Russian).
Tinenkova D. Kh. and Petrenko E. L. (2003) Description of zooplankton in the coastal areas of the middle and southern Caspian in summer 2002. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2002(KaspNIRKh Publishing, Astrakhan) pp. 560 pp. 144–147 (in Russian).
Tinenkova D. Kh. and Petrenko E. L. (2004) Description of zooplankton in the middle and southern Caspian in October 2003. Fisheries Researches in the Caspian: Scientific-Research Works Results for 2003(KaspNIRKh Publishing, Astrakhan) pp. 130–131 570 pp. (in Russian).
Tinenkova D. Kh. and Pochitaeva M. M. (1985) The feeding of the Caspian kilka. The Caspian Sea: Fauna and Biological Productivity(Nauka, Moscow) pp. 220–224 277 pp. (in Russian).
Tkach A. V., Gordina A. D., Niermann U., Kideys A. E., Zaika V. E. (1998) Changes in the larval nutrition of the Black Sea fishes with respect to plankton. In Ivanov L. I. and Oguz T. (Eds.). Ecosystem Modelling as a Management Tool for the Black Sea, 1(Kluwer, Dordrecht) pp. 235–248.
Volovik S. P. (2000) The Ctenophore Mnemiopsis leidyi (A. Agassiz) in the Azov and Black Seas: Biology and Consequences of its Intrusion. AzNIRKh, Rostov-on-Don 498.
Vostokov S. V., Ushivtsev V. B., Lisitsyn B. E., Solovyev D. M. (2002) The state of the ctenophore Mnemiopsis leidyi population in the Caspian Sea in summer 2001 and its relation to environmental conditions. Caspian Floating University Research Bulletin 3:127–138 (in Russian).
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||