Total lipids in anchovy and sprat were measured and interpreted as indicators of their nutritional condition and food supply for the period 2005 to 2010. High lipid content in anchovies suggested that they were able to found sufficient food and favorable environmental condition supporting their stock biomass on a certain level which was strongly limited by heavy fishing. Wide inter-annual fluctuations in anchovy landings could be caused by variability in yearly recruitment and due to shifts in the spatial distribution patterns of the exploited stock. Unlike anchovy, lipid reserves in sprat declined remarkably to the lowest levels recorded during the 50-year observations period. Such a significant worsening in sprat nutritional condition followed the evident warming of the Black Sea and coincided with a sharp decline in sprat catches off Crimea. Thus, the deterioration of food supply together with intensive fishing could have contributed to the reduction of that local sprat stock.
The food supply of the Black Sea sprat Sprattus sprattus phalericus off the Crimea coast in the feeding periods of 2006-2013 was studied. The level of accumulation of storage lipids in the fish body and the content of essential polyunsaturated fatty acids (eicosapentaenoic and docosahexaenoic) served as criteria of food supply. It is shown that the average annual content of sprat total lipids varies over a wide range (4.5-9.5% of wet body weight) due to changes in the storage lipid content (58-71% of total lipids). The content of eicosapentaenoic and docosahexaenoic acids (101-451 and 123-622 mg/100 g wet weight, respectively) is positively correlated with the level of storage lipid accumulation in the body. The interannual variability in the content of lipids and fatty acids is determined not only by the quantity but also the qualitative composition of consumed food (namely, the proportion of planktonic organisms of the cold-water and warm-water complexes). The possible influence of the interannual variability in the composition of forage mesoplankton on the condition of the Black Sea sprat off the Crimea coast is discussed.
Biological parameters of Azov anchovy from commercial catches in 2016/2017 and 2017/2018 fishing seasons were studied. During the first season, fishery was mainly based on fish of the 1st age group with an average length of 10.9 cm TL, while in 2017/2018 on 2-year-old fish with length of 11.4 cm. Parameters of the length-weight relationship were not different between sexes: for fish < 9.5 cm TL a = 0.00126, b = 3.719, and for fish ≥ 9.5 cm a = 0.0207, b = 2.475. The sex ratio in overall was close to 1:1. The relative condition factor Kn and total lipids content were higher in October-November 2017/2018 than in 2016/2017 and gradually decreased to February-March in both seasons. The growth rate was also slightly higher in 2017/2018. For both seasons, growth parameters in the von Bertalanffy equation were estimated as L∞ = 13.0 cm, W∞ = 12.6 g, K = 0.73 yr-1 , to =-0.86 yr. Azov anchovy is lighter in weight than the Black Sea anchovy at the same length. The growth rate of Azov anchovy seems to be similar to the Black Sea anchovy for age groups 0 and 1, but declined as fish getting older.
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