黄海大头鳕幼鱼的生长和分布特征

作为黄海的代表性冷温性鱼类,大头鳕(Gadus macrocephalus)的资源量近年逐渐上升趋势,其中幼鱼所占比重较大,种群丰度及补充都受到黄海冷水团的影响,作为2龄性成熟鱼种,探究其当年生和非当年生幼鱼分布和生长的季节变化及与黄海冷水团的关系对了解大头鳕的资源变动有重要意义。本研究基于2016年10月、2017年5和8月的调查结果,分析了黄海冷水团存在时期的海洋环境特征与大头鳕幼鱼分布及生长特征的关系。研究显示,春季,幼鱼主要分布于青海渔场、石岛渔场和连青石渔场,非当年生幼鱼和当年生幼鱼随栖息地水深分别呈东西两区块分布。夏季,幼鱼主要位于122.00°E以东、底温低于10℃的黄海中部较深海域,有少部分分布于黄海北部,这与黄海冷水团强盛时期南北低温中心的位置有关。秋季,黄海北部大头鳕幼鱼的渔获量明显减少,仅在石岛渔场和连青石渔场大头鳕的种群密度仍较高。广义相加模型(Generalized Additive Models,GAM)分析结果显示,温度和盐度对大头鳕幼鱼的资源丰度指数(单位捕捞努力量渔获量(Catch Per Unit Effort,CPUE))有显著影响,当栖息地水域盐度在31.90和32.80附近,底温在8.5℃左右时,大头鳕幼鱼的CPUE较高。体长-体重关系显示,春季,幼鱼呈负异速生长,夏秋季呈正异速生长,黄海冷水团强盛时期较高的有机质含量及初级生产力造成的丰富饵料可能是导致大头鳕夏秋季b值较高的原因,因此黄海冷水团的季节变化对大头鳕的分布和生长均有显著影响。

Growth and Distribution of Young Pacific Cod in Yellow Sea

As a typical cold-temperate fish species in Yellow Sea,the catch of Pacific cod(Gadus microcephalus)showed a rising trend in recent years,among the caught,the young individuals accounted for a large proportion.The abundance and recruitment of this species are affected by Yellow Sea Cold Water Mass(YSCWM).G.microcephalus matures at age two.Exploring the influence of YSCWM on the seasonal variation of the distribution and growth of young cod is important for understanding the population dynamics.Based on the surveys in October 2016,May and August 2017,we analyzed the relationship between the marine environment and the distribution and growth of young cod during the appearance of YSCWM.The results showed that young cod distributed mainly in Qinghai,Shidao and Lianqingshi fishing grounds in spring.One-year-old and young-of-the-year individuals distributed in the east and west areas of the Yellow Sea,respectively,with the increasing habitat depth.In summer,young cod were found mainly in the east of 122.00°E areas of the central Yellow Sea where bottom water temperature was below 10℃.Beyond that,a small part distributed in the northern part of the Yellow Sea,which was related to the low-temperature centers of the YSCWM.The catch of G.microcephalus in the northern Yellow Sea was significantly decreased in autumn,and its density was high only in Shidao and Lianqingshi fishing grounds.Generalized Additive Model(GAM)showed that bottom water temperature and bottom salinity had significant effects on the resource abundance index(catch per unit effort,CPUE)of the young cod.The highest CPUE area was in the region where the bottom salinity was about 31.90 and 32.80 and the bottom temperature was 8.5℃.The length-weight relationship showed that young cod were in a positive allometric growth in spring and negative allometric growth in summer and autumn.The high content of organic matter and primary productivity were the main reasons leading to the highest allometric factor b in summer.