东海区太平洋褶柔鱼生殖群体结构特征的季节差异

依据1997~1999年东海区春、夏、秋3个季节的底拖网资料,分析了东海区太平洋褶柔鱼生殖群体的性别组成、性腺成熟度和初次性成熟胴长等群体结构特征。结果表明:在东海区春、夏、秋三季均存在太平洋褶柔鱼的生殖群体。各季节生殖群体的雌雄比例均不符合1∶1的关系(P<0.05),雌性比例小于雄性。生殖群体中性成熟个体胴长的季节性变化较为明显,雌、雄平均胴长均以秋季最大,夏季最小。雌性个体的平均胴长均显著大于雄性。各季节太平洋褶柔鱼生殖群体中胴长与体重关系的性别差异极显著(P<0.01)。此外,不同季节雌、雄太平洋褶柔鱼的初次性成熟胴长差异较大,雌性为:春季223.4 mm、夏季170.4 mm、秋季202.3 mm;雄性为:春季174.0 mm、夏季164.3 mm、秋季165.3 mm。雄性初次性成熟胴长小于雌性,夏季雌、雄初次成熟胴长均小于春、秋季。依据春季生殖群体的胴长范围、初次性成熟胴长等群体结构特征推测,在东海区可能存在着小规模的春生群。

Seasonal differences in the stock structure of mature Todarodes pacificus in the East China Sea Region

Based on the data taken from bottom trawl fishery resources survey in the East China Sea Region in spring, summer and autumn from 1997 to 1999, stock structure of mature Todarodes pacificus , including sex ratio, maturity stage and size at first maturity were analyzed. The results indicated that there were mature populations of Todarodes pacificus in all three seasons. Sex ratio of mature females to males was not kept at 1∶1 (P> 0.05). The mature females were always less than their male counterparts. The seasonal variation of mantle length of mature individuals was obvious, with the maximum in autumn and the minimum in summer (both males and females). The results showed that the average mantle length of mature males was shorter than that of the females. And sexual variations in the relationship between mantle length and body weight in mature populations were very significant in each season ( P < 0.01). Moreover, the difference of the size at first maturity between females and males was significant in all three seasons. The size at first maturity for females was 223.4 mm in spring, 170.4 mm in summer and 202.3 mm in autumn, respectively. And it was 174.0 mm in spring, 164.3 mm in summer and 165.3 mm in autumn for males. The size at first maturity for males was smaller than that for females in all three seasons, and the size at first maturity for both males and females in summer was smaller than that in spring and autumn. Based on the characteristics of mature stock structure in spring, the conclusion that there was a small-scale spring spawning group in the East China Sea Region was drawn out.