Abstract
The annual reproductive cycle of a small flounder (aramegarei), Tarphops oligolepis, was examined in Wakasa Bay from the appearance of recently settled juveniles in the field and the female maturity during a year. Seasonal changes in the distribution of standard length indicated the presence of two spawning periods, July and October, when small juveniles appeared in the nursery ground. In females, gonadsomatic index (GSI) showed a peak (10.8) in spring, decreased to a low level in September (1.1), increased again to form another peak in November (8.3), and declined during winter (2.5). According to the histological observation on ovaries, matured oocytes were also found in two seasons in a year; from April to June and from October to December. From those results, it is concluded that aramegarei of Wakasa Bay has semi-annual reproductive cycle with two spawning seasons in a year; spring and autumn. Moreover, it takes only half a year to spawn at the first time, especially for the fish born in spring. This small flounder, lives in coastal areas and is easily caught, with unique characteristics of maturation, can be a good model for reproductive physiology and ecology of fishes.
