渤海小黄鱼生长特征的变化

根据1960年、1982年、1993年和2003年各年春季对渤海进行的底拖网调查获得的小黄鱼（Pseudosciaena polyactis Bleeker）生物学数据，对4个不同年代间渤海小黄鱼的群体组成、生长状况等生物学特征的年代间变化进行分析，结果表明，渤海小黄鱼的生物学特征在这4个年代间发生了明显变化。自1982年以来，渤海小黄鱼群体结构呈现个体小型化、低龄化、生长加快、渐近体长和渐近体质量减小、体质量生长拐点提前等现象。小黄鱼生物学特征因子的年代间变化，可能与渔业资源不断衰退以及小黄鱼自身对外界环境因素变化的适应有关。

Growth variations of small yellow croaker (Pseudosciaena polyactis Bleeker) in the Bohai Sea

Small yellow croaker(Pseudosciaena polyatics bleeker) is a warm-temperate species and one of the most important commercially exploited fish in China,which is distributed in the Bohai Sea, the Yellow Sea and the East China Sea.Previous authors have described an increase in growth parameters of small yellow croaker from 1958 to 1964,the characteristics of growth for Spanish mackerel underyearing in the Yellow Sea and the Bohai Sea,and individual absolute fecundity of Anchovy during 2002-2004 and the relationships between individual absolute fecundity and its fork length,net body weight and age which varied significantly as compared with those during 1985-1986.These phenomena possibly have been related to long-term over-fishing pressure and the changed habitat environment.Based on the bottom trawl surveys in the Bohai Sea during the spawning season of springs in 1960,1982,1993 and 2003,the growth characteristics and its decadal changes in the population structure of the species were analyzed in this study.The results show that the growth characteristics of small yellow croaker in the Bohai Sea have obviously changed during four decades,including miniaturization and simplifying of age and length composition.The mean body length reduced from 205.8mm in 1960 to 143.3mm in 1982,136.6mm in 1993,and 130.3mm in 2003,respectively;the mean body weight reduced from 161g in 1960 to 48g in 1993,and 34g in 2003,respectively;the mean age reduced from 3.8a in 1960 to 2.1a in 1982,1.6a in 1993 and 1.3a in 2003,respectively.The exponent b of the length-weight relationship function decreased significantly (P<0.01) with time,and the growth coefficient increased from 0.281 in 1960 to 0.325 in 1982,0.460 in 1993 and 0.495 in 2003,respectively.The above results indicated that the growth rate increased.Studies on age composition,body length composition,growth and their derived growth parameters are indispensable in determining stock dynamics.The variations in population structure and growth characteristics of small yellow croaker in the Bohai Sea in the past four decades were possibly caused by long-term over-fishing pressure,stocks are adaptively response to the habitat environment changed.