Известия ТИНРО (Dec 2017)
Reproductive cycle and the scale of gonad maturity for rock sole <i>Lepidopsetta polyxystra</i>
Abstract
The gonad maturity scale for rock sole Lepidopsetta polyxystra is presented in tabular form. Its reproductive cycle is described on the base of histological studies and analysis of seasonal occurrence of the species individuals with gonads at certain stages of maturity, in comparison with dynamics of the gonad-somatic index. Four phases are determined in the reproductive cycle. The first phase continues until the start of sexual cells maturing in the age 4-5 years (maturity stages I and II) - these juvenile fish live in the coastal shallow waters and are practically absent in trawl catches. Other three phases repeat annually. During the second phase, the rock sole gonads restore after previous spawning (stage VI) and begin the maturing for the next one (stage III, with yolked oocytes appearance in female gonads). This phase continues 8-9 months, usually from March to November-December and associates with active feeding when fish refill their energetic losses. The third phase is the time of fast maturing of gonads (stage IV, with active yolk producing and accumulation in oocytes and mass forming of spermatozoids) during wintering, when accumulated energetic resources are transformed to maintenance of the reproductive system. This phase starts from the moment of divergence between the reserve and reproductive funds of sexual cells in female gonads and continues 2-3 months. The fourth phase is the spawning (maturity stage V). It continues 1.0-1.5 months, usually with the peak of spawning in April.
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