Effect of Sea Water Temperature on Variability of Batch Fecundity in Japanese Anchovy from Coastal Waters around Miura Peninsula, Central Japan

Abstract

Batch fecundity (BF) of Japanese anchovy was estimated by analysis of ovarian egg size frequency around Miura Peninsula, in April through June in 1982 (a 'warm' year) and in 1984 (a 'cold' year). Total number of yolked eggs in an ovary (NT) increased with body size, showing variability in relation to GI. In 1982, the mean of relative NT (NTR = NT/SL3 × 103) ranged from 22600 to 29400 with a maximum in May. In 1984 markedly lower values of 14500 in May and 16000 in June were observed. Estimated mean ± S.D. of relative batch fecundity (BFR = BF/SL3 × 103) in 1982 was 3400 ± 900 in April, 7700 ± 2300 in May, and 8400 ± 2000 in June. These values were lower in 1984 than the same months in 1982, as 3400 ± 1500 in May and 6500 ± 2000 in June. The mean of BFR increased with increasing sea surface temperature (SST), showing a regression of BFR = - 11200 + 910 × SST. We suggest that sea water temperature controls anchovy egg production, as large eggs in fewer numbers occur at low temperatures and higher numbers but smaller eggs at higher temperatures. Batch fecundity varied, showing high values with high NT and GI in May 1982. In 1984, batch fecundity was reduced by the enlarged size of eggs of both egg groups which was influenced by the extremely low temperatures.