A three-dimensional bioenergetic population model of anchovy and sprat in the Black Sea. Hindcast (1960-2020) and sensitivity simulations

This study presents the development of a three-dimensional, Wisconsin-type bioenergetic/population model, two-way coupled with a biogeochemical model (POM-ERSEM) that simulates physical, chemical, and biological processes in the marine environment, to investigate the dynamics of anchovy ( Engraulis encrasicolus ) and sprat ( Sprattus sprattus )—the two most ecologically and economically significant fish species in the Black Sea. The model simulates key energetic processes, including growth and reproduction, and, in conjunction with the population module, it was used to estimate the two species biomass spatiotemporal variability. A long-term simulation over 1960–2020 period was performed, using ECMWF ERA5 atmospheric forcing. The model successfully reproduces the interannual variability in both species’ stocks and highlights the formation of distinct anchovy and sprat habitats. To explore the effects of atmospheric forcing, a perpetual simulation for the same period was conducted. The analysis reveals a negative correlation between sea surface temperature and anchovy biomass, primarily due to reduced adult weight and increased energetic demands, which negatively impact productivity. In contrast, sprat populations exhibit a positive response to warming, with increased survival rates across life stages despite a decline in egg productivity due to habitat limitations. Furthermore, the study examines the species responses to varying fishing pressure. While both species and especially sprat, are threatened by overfishing, they demonstrate rapid recovery rates, indicating susceptibility to effective management measures. These findings provide valuable insights into the sustainable exploitation of anchovy and sprat under changing climatic conditions, aiding in the development of adaptive fisheries management strategies.