Intra-Decadal (2012–2021) Dynamics of Spatial Ichthyoplankton Distribution in Sevastopol Bay (Black Sea) Affected by Hydrometeorological Factors

SIMPLE SUMMARY: Due to the high mortality of fish in the early stages of ontogenesis, the detection of factors affecting it seems to be an extremely important problem. We investigated intra-decadal dynamics and spatial distribution of the ichthyoplankton abundance that depends on hydrometeorological factors. We focused on Sevastopol Bay and its four areas. The ichthyoplankton distribution by areas of Sevastopol Bay was associated with the peculiarities of the pollution distribution and with the wind regime. For the first time, a positive effect of temperature and repeatability of northern and northeastern winds on the ichthyoplankton number during the summer spawning in all areas was reported. The abundance of ichthyoplankton is influenced by several factors: (a) In the southern area, a positive influence of temperature and northerly winds on the ichthyoplankton abundance was confirmed. (b) In the eastern area, the discharge of rivers is an additional factor. (c) Characteristics of winds in western and central areas are significantly impacted by the orography peculiarities. The data obtained during the research highlighted the importance of comprehensive monitoring studies using an intra-decadal approach on scrutinizing ichthyoplankton abundance, distribution and many other characteristics. ABSTRACT: High mortality of fish in the early stages of ontogenesis requires the detection of factors affecting it and is an extremely important problem. For this reason, we tried to consider the influence of some hydrometeorological factors on the intra-decadal dynamics and spatial distribution of ichthyoplankton abundance in Sevastopol Bay. To this end, we analyzed ichthyoplankton samples collected in 2012–2021 in Sevastopol Bay, and the four districts were identified. The ichthyoplankton distribution by areas was associated with the peculiarities of the pollution distribution. The maximum numbers in eggs (34.7 ± 7.5 ind. m(−2)) and larvae (10.0 ± 2.4 ind. m(−2)) were recorded in July–August. For the first time, a positive effect of temperature and repeatability of north and northeast winds on the ichthyoplankton number during the summer spawning in all identified areas of Sevastopol Bay using principal component analysis (PCA) was reported. In the southern region, positive influence of temperature and northerly winds on the ichthyoplankton abundance was confirmed by ANOVA (p = 0.02), and Pearson’s correlation analysis revealed significant correlations between these parameters on inter-annual scale (r > 0.5). In the eastern area, the discharge of rivers is an additional factor affecting the abundance of ichthyoplankton, while in the western and central areas, these factors were the wind characteristics caused by the orography peculiarities. The pollution spread in Sevastopol Bay is also largely due to the wind regime. The importance of comprehensive monitoring studies using intra-decadal data on ichthyoplankton is emphasized.