黄海中南部小黄鱼种群生物学特征的季节变化和年际变化

Seasonal and annual variations in biological characteristics of small yellow croaker Larimichthys polyactis in the central and southern Yellow Sea

根据2000～2010年"北斗"号调查船在黄海中南部水域8个航次的渔业生物底拖网调查数据,结合1985～1986年的历史资料,对该水域小黄鱼种群的生长、摄食、繁殖及资源量变动等生物学特征的季节变化和年际变化进行研究。结果表明,小黄鱼春季平均体长和优势体长范围要高于其他季节,从2000～2010年在同一季节小黄鱼的平均体长和优势体长降低,并且优势体长更为集中。小黄鱼食物组成从1985～1986年到2000年发生了显著的变化,2000～2010年小黄鱼食物组成变化不大。1985～1986年小黄鱼食物主要是以鳀Engraulis japonicus(重量百分比为45.18%)为主,其次是小型底栖虾类。2000年和2010年小黄鱼食物组成主要以太平洋磷虾Euphausia pacifica为主,占食物总量的47.28%,其次是细螯虾Leptochela gracilis和脊腹褐虾Crangon affinis,但是鳀在食物组成中从4.67%增加至10.64%。小黄鱼各个季节性腺发育Ⅱ期所占的比例较高。2000年小黄鱼平均渔获量最高(夏季除外),2000年以后其平均渔获量降低,其分布开始向北偏移。由上可知,黄海小黄鱼的种群属性及其生活史类型已经发生变化。因此,建议小黄鱼的渔业管理和资源养护要充分考虑其生物学特征的变化。

Based on the data collected from bottom trawl in eight cruises by R/V ＂Beidou＂ in the central and southern Yellow Sea from 2000 to 2010 and historical data from 1985 to 1986, seasonal and annual variations in the growth, feeding habits, reproductive characteristics of small yellow croaker Larimichthys polyactis and the dynamics of its resource were analyzed. The results were as follows, the average body length and the dominant body length range in spring were higher than those in the other seasons, and showed a decreasing trend from 2000 to 2010 with narrower dominant body length spectra. The food composition of small yellow croak- er greatly changed from 1985~1986 to 2000, but no significant changes were found from 2000 to 2010. Japanese anchovy EngrauZis japonicus was the predominant diet in 1985~1986, ac- counting for 45.18G of the total weight of the diets, then was the small-sized shrimps. In 2000 and 2010, Euphausia pacifica was the main diet, accounting for 47.28% and 37.20%, respec- tively, then were Crangon a f finis and Leptochela gracilis. In addition, the proportion of Japa- nese anchovy in food composition increased from 4.67% in 2000 to 10.64G in 2010. The pro- portions of individuals with gonad development at stage II in 2000s were less than those during 2007---2010. The mean catch of small yellow croaker was the highest in the 2000s （excluding summer）, but the relative abundance gradually decreased since the 2000s. In addition, the dis- tribution of small yellow croaker gradually migrated northward. The impacts of human activities and environment changes on fishery resource become more and more serious, thus the attribute of small yellow croaker population and its life history characteristics in the Yellow Sea greatly changed. So, variations in biological characteristics of small yellow croaker should be fully con- sidered in fishery resource management and conservation.