The long-term ichthyoplankton abundance summer trends in the coastal waters of the Black Sea under conditions of hydrometeorological changes

Abstract

In this study a long-term literature and field-monitoring dataset collected from the Sevastopol coast in the Black Sea during summer seasons from 1960 to 2017 were examined. Principal component analysis (PCA) and ANOVA analysis clearly demonstrate changes in the dynamics of ichthyoplankton abundance due to wind conditions, temperature, and salinity. The results specifically showed significant relationship between the abundance of eggs (r = 0.82) and repeatability northeasterly winds and between larvae abundance and speed northeasterly wind (r = 0.64). As the wind speed increases, the surface water temperature decreases and salinity rises. According to the data on the temperature and wind speed, the period of occurrence of local upwellings in summer near the coast of Sevastopol was determined ~8 and 20–25 years. Based on analysis of linear trends for the summer periods from 1960 to 2017 in this area a decrease in the number of fish eggs and occurrences of larvae and a general reduction in temperatures, salinity, speed and repeatability northeasterly winds was observed. Long-term ichthyoplankton data monitoring can be used to validate model results and provide further predictions of changes in ecosystem components.