长江口及浙江沿海花鲈的繁殖生物学

THE REPRODUCTIVE BIOLOGY OF LATEOLABRAX JAPONICUS IN THE YANGTZE RIVER ESTUARY AND ZHEJIANG OFFSHORE WATERS

本文研究了花鲈卵巢的发育、产卵类型、产卵期、繁殖水域及雌雄同体现象等．根据长江口及浙江沿海花鲈卵巢的周年组织学切片，将卵巢划分为Ⅵ期，还有重复发育的Ⅵ－Ⅳ＇期（或Ⅳ＇期）和Ⅴ＇期，属分批非同步型产卵类型。在繁殖季节，短期内可以产两次卵，产卵期为１１月至翌年１月，盛产期约为１１月中至１２月中的一个月内。性成熟年龄，雌鱼为Ⅳ龄，雄鱼为Ⅱ龄，有雌雄同体现象。在邻近沿海和长江口盐度较高水域产卵，盐度为２２—２６‰。

A study has been conducted on the maturation of ovary,spawningtype,ages of maturity, spawning waters and hermaphroditism of Lateolabrax japonicus (Cuvier et Valoncinnes).The course of ovarian maturation is divided into sixstages and a recovered stage VI-IV' or IV'. Stage 1-Juveniles; stage Ⅱ-includingimmature and recovered ovaries; stage Ⅲ-ripening ovaries; stage Ⅳ-nearly ripovaries; stage V-ripe ovaries; stage Ⅵ-spent ovaries. After the fish released thefirst batch of eggs,the ovaries regenerate into stage Ⅵ-Ⅳ' (or Ⅳ'),which continue to develop rapidly into stage Ⅴ'. About half a month later the ovaries developinto stage Ⅴ'. If enviromental conditions are appropriate, then the another spawnmay take place. This fish are released two batches in a breeding season. The ovaries develop to stage Ⅲ in October as the age at first maturity, stage Ⅳ in Novemiber. The mature fish spawn at the middle of November and continue to Januaryof the next year. The fish spawn in the waters of the Yangtze River estuary andits adjacency with higher salinity nearby marine water. The salinity is about 2226%. The female and male reach the first maturity at 4 ages and 2 ages in yearold respectively. The individual absolute fecundity ranges from 312928-2211000eggs, averaging 1282327 eggs, and the individual relative fecundity ranges from185. 27-847. 71 eggs, averaging 408. 03 eggs.