Life cycle of the pelagic goby Aphia minuta (Pisces : Gobiidae)

Reproductive aspects of the transparent goby Aphia minuta (n=2977, 14-45 mm total length (TL)) were studied in Majorcan waters, western Mediterranean, during the fishing season (December to April) from 1985 to 1993. Male:fema le sex ratio was 1:1. Size at first maturity was 38 nun TL for females and 34 nun TL for ma-les. Oocyte size-frequency distribution indicated that A. minuta is a single spawner. Fecundity of A. minuta ranged from 935 to 2648 oocytes. The breeding season extended from December to April with a peak in March. After a single reproduction at 5-6 months of age, most of the speci mens disappeared from the fishing areas. Recruitment to the fishing area oc curred in late December and early January (14-24 mm TL, age 2-3 months). On the other hand, the hatch date back-calculated from the age in days and th e date of capture of individuals of A. minuta during the fishing season, in dicated a spawning peak in autumn (September-October), six months after the peak of observed spawning. Schools of A. minuta were detected by acoustic methods, during the fishing season (winter-spring) in fishing areas (5-40 m depth), principally inside bays, and during the rest of the year (summer a nd autumn) in deeper areas (40-90 m), outside bays, with water temperatures between 13 and 16 degreesC and a high seasonal productivity in each depth range. Therefore, we propose that A. minuta has two annual cohorts in the w estern Mediterranean, corresponding to two main spawning in spring and autu mn, respectively. Life history pattern indicated that we only know the wint er cohort resulting from the autumn spawning. Meanwhile the summer cohort ( spring spawning) grows and reproduces in deeper areas not being targeted by the fishery. Indirect validation is provided from information from other a reas. The relevance of the life cycle is discussed in relation to fishery m anagement.