チチブTridentiger obscurusの生殖年周期〔英文〕

概要

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To clarify the whole aspect of the annual reproductive cycle of the chichibu-goby Tridentiger obscurus, we examined the seasonal gonadal changes of adult fish caught from its natural habitat, and the participation of underyearling fish in repoduction under laboratory conditions.Seasonal changes in GSI and gonadal histology of adult fish indicate that the annual reproductive cycle can be divided into four phases: the resting period in September and October (phase 1), the period from November to February when yolk vesicles appear in ovaries and testes are in moderately active spermatogenesis (phase 2), the period in March and April when yolk globules are accumulated and spermatogenesis is further activated (phase 3), and the spawning period from May to August (phase 4).The underyearling fish come to mature within the spawning period in which they have been born, only if they grow to a critical size in time. The critical total length is estimated to be 35mm in females and 45mm in males.