Effect of Certain Abiotic and Biotic Factors on Spawning of the European Sprat Sprattus sprattus (Linnaeus, 1758) in the Black Sea in November 2016–2017

Abstract—The study examines changes in the abundance (density) and distribution of European Sprattus sprattus (Linnaeus, 1758) eggs and larvae, as well as the phenology of its spawning depending on hydrologic factors and abundance of gelatinous macroplankton in the Black Sea in November 2016–2017. An increase in temperature of the sea surface layer observed since the beginning of the century and the enhanced heat content of the cold intermediate layer contributed to the preservation of warm-water mesozooplankton at the end of the fall hydrologic season, which provided favorable trophic conditions for all planktophages. The biomass of scyphomedusa Aurelia aurita was the third largest in the gelatinous macroplankton in 2016 and the largest in 2017 for the long-term annual research in fall months. Gelatinous macroplankton, however, did not have a significant impact on the survival of sprat in the early stages of its development. The average number of sprat eggs and larvae in November 2016 (184 and 11 ind/m², respectively) and November 2017 (268 and 21 ind/m², respectively) exceeded their maximum values recorded in the 1950s. The larvae did not differ in length composition in the beginning of the spawning season in 2016 and 2017.