Marked interannual differences in reproductive parameters and daily egg production of anchovy in the northern Aegean Sea

In the present paper, an overview of the application of the Daily Egg Production Method (DEPM) to the northern Aegean Sea anchovy stock is presented, and reproductive parameters are compared in the framework of ambient oceanographic regimes. The DEPM was applied twice : in June 1993 and June 1995. Data collection was based on bongo-net ichthyoplankton surveys and concurrent adult surveys onboard the commercial fishing fleet. Revised, more precise estimates of the daily egg production are presented based on the inclusion of both eggs and yolksac stages in the estimation procedure (fit of single embryonic mortality curves). Remarkable between-years differences in the daily egg production, batch fecundity and spawning frequency were found. These parameters were significantly higher in June 1993 than in June 1995. In June 1993, waters were colder, less saline and richer in zooplankton compared to 1995. Adult somatic condition and egg size were also higher in June 1993 than in 1995. These findings emphasize the importance of adult prey availability in determining anchovy egg production.