فهرست نشریات علمی دسترسی آزاد ایران

This study aimed to assess the effects of various environmental factors, including sea surface level (SSL), seawater surface temperature (SST), the East Atlantic-West Russian pattern (EA_WR), river discharges (RD), and one human activity, fishing effort (E) on the variability of Clupeonella caspia bio-indicators over the last 27 years, using 118604 specimens. To analyze the data, dynamic factor analysis (DFA) was applied to parameters such as catch, abundance, spawning stock biomass (SSB), the percentage of immature individuals (Immature), the percentage of mega spawners (Mega), and the relative condition factor (Kn) derived from C. caspia datasets. Throughout the study period, catch, abundance, SSB, Mega, and Kn exhibited increasing trends, whereas the Immature displayed a decreasing one. Among the 324 models examined, the best-fit model featured a "diagonal and unequal" matrix and utilized SSL as an exploratory covariate, revealing two common trends. The first trend demonstrated a positive correlation with catch, abundance, SSB, and Mega, while negatively correlating with the percentage of immature individuals. The second trend showed a positive relationship solely with Kn. Additionally, catch, abundance, SSB, Mega, and Kn were positively correlated with SST but negatively with SSL. In contrast to two other kilka species, C. engraliformis and C. grimmi, C. caspia exhibits a distinct pattern; despite a decline in SSL and an increase in SST, its catch, abundance, and SSB all demonstrate an upward trajectory. Based on the indicators of Mega and Immature, the population structure of C. caspia appears to be relatively healthy.