Life history of sprat (Sprattus sprattus) in the Black Sea under warming and fishing: current state and patterns of variability.

Abstract

Sprat Sprattus sprattus (Linnaeus, 1758) is one of the most significant commercial fish species in the Black Sea. This study examines the sex ratio, size-age structure, growth, and mortality of sprat in the waters of Crimea from 2021 to 2023. The paper discusses the geographic variability and the influence of temperature, food availability, and fishing pressure on the life history of this species. In total, 2113 individuals from commercial catches were examined. The sex ratio was slightly skewed towards females (1:0.83). The maximum total length for both males and females was 10.0 cm, with a maximum weight of 8.51 g for females and 6.73 g for males. The lifespan for both sexes was 4 years. The Bertalanffy growth equation parameters were calculated, with L_∞ = 13.79 cm, W_∞ = 16.3 g, K = 0.237 year^-1 and t₀ = -1.53 year. The exponent value in the length-weight relationship was 3.14 (positive allometric relationship). The total, natural and fishing mortality coefficients for both sexes were 2.13, 0.65 and 1.48 year^-1, respectively, and the exploitation ratio was 0.70, indicating excessive fishing pressure. It was determined that sprat from lower latitudes had smaller sizes, slower growth rates and shorter lifespans compared to sprat from higher latitudes. A strong negative correlation was found between the size and lifespan of sprat and sea surface temperature. Excessive fishing pressure against the backdrop of climate warming was identified as the cause of the reduction in lifespan and size of sprat in the Black Sea, therefore it is recommended to reduce the volume of sprat fishing and increase its minimum landing size to preserve the population of sprat in the Black Sea.