Reproductive characteristics of Japanese anchovy, Engraulis japonicus, in two bays of Japan

The reproductive characteristics of Japanese anchovy, Engraulis japonicus, were studied in Osaka Bay and Wakasa Bay, which are located on each side of Japan. The length of spawning season varied between two bays: 8 months (between April and November) in Osaka Bay and 4 months (between May and August) in Wakasa Bay. The seasonal temperature profiles suggested that not only the onset of spawning in both bays but also the end of spawning in Osaka Bay are highly temperature-dependent, and that the critical temperature is about 15 degreesC. On the other hand, Osaka Bay anchovy collected after July were composed of only small ones (smaller than 10.5 cm body length). A comparison of length-weight relationships revealed a better body condition of small Osaka Bay fish than Wakasa Bay fish. It is likely that the Japanese anchovy in Wakasa Bay ceases spawning as early as September in spite of a high temperature, due to their poor nutritional condition. Estimated spawning frequency ranged from 0.40 to 0.88 for Osaka Bay females and from 0.22 to 0.62 for Wakasa Bay females. These values indicate that the Japanese anchovy from two bays spawn at similar intervals of 1.13-2.50 and 1.61-4.55 days. The sizes at first maturity in Osaka Bay and Wakasa Bay were estimated as 7.38 and 8.53 cm, respectively. These reproductive characteristics are compared and contrasted with those described for the Japanese anchovy in Sagami Bay. (C) 2004 Elsevier B.V. All rights reserved.