Some Factors Influencing Early Survival and Abundance of Clupeonella in the Sea of Azov

Abstract

Some regularities in the abundance fluctuations the Azov 'tiulka' (Clupeonella delicatula} have been established as a result or a study of the effect of various environmental factors on year-class strength. The factors considered included salinity, sea condition, light intensity, O Sub(2) and temp regimes, and feeding conditions of larval fish. A method of determining the significance of one factor when other factors are at an optimum level was used, which made it possible to establish the dominant importance of the temp regime during embryonic development. It has been found that poor year classes are formed in years when temps optimal for the development of eggs (15-l8{degree}C) continue for 10 days, while there is a sharp increase in year-class strength when these favourable temps continue for an average of 20 days