长江靖江段沿岸日本鳗鲡丰度的时间格局及生物学研究

于2002—2017年在长江靖江段沿岸对日本鳗鲡资源量进行长期调查, 对其丰度的时间格局特征及环境影响因素等进行了分析。结果显示, 在近16年519次调查中, 采集到日本鳗鲡137尾, 平均年龄(1.8±1.0)龄, 平均全长和体质量分别为(31.1±9.8) cm和(57.64±91.94) g, 89.1%的个体未性成熟, 94.9%的个体处于黄鳗期。全长与体质量关系式为: W=0.0002415×L3.483 (r2=0.9537, n=137)。日本鳗鲡在靖江段渔获物中的数量百分比与重量百分比分别仅为0.08%和0.69%, 且丰度和出现率在年间均呈波动式递减趋势。同时发现靖江段日本鳗鲡丰度年际波动与长江口鳗苗群体补充无关, 其出现率受水温及水质因子氨氮和浑浊度的影响。

THE TEMPORAL DISTRIBUTION AND BIOLOGICAL CHARACTERISTICS OF ANGUILLA JAPONICA COLLECTED AT THE JINGJIANG SECTION OF THE YANGTZE RIVER

Based on long-term survey data,this study analyzed resource status and distribution pattern of Japanese eel collected at Jingjiang section of the Yangtze River using a combination set-net consisting of a 40-meter net wall(mesh size:1.8 cm)and two fyke nets(mesh size:0.9 cm)from January 2012 to December 2017.Our results indicated that a total of 137 Anguilla japonica with an average age of(1.8±1.0)years were collected from 519 samplings within 16 years,of which 89.1% individuals were sexually immature.The average total length and body weight were(31.1±9.8)cm and(57.64±91.94)g,respectively,of which 94.9% of individuals were in yellow eel stage.The relationship between total length and body weight was W=0.0002415×L^3.483,and the coefficient of determination(R²)was 0.9537.Japanese eels can migrate to the Jingjiang section of the Yangtze River with 0.08% by individuals and 0.69% by weight,respectively,and the abundance and incidence rates showed a declining trend with time.In addition,cross-correlation analysis showed that the abundance of Japanese eel collected in the Jingjiang section were not related to recruitment of Anguilla japonica glass eels in the Yangtze River estuary.The results indicated that the wild Anguilla japonica resources in the Yangtze River were extremely rare and need to be protected.The generalized additive model showed that the occurrence rate of Japanese eel was affected by water temperature,ammonia nitrogen and turbidity.Pollution of the water environment may affect the survival of glass eels successfully migrated to the Jingjiang section.