浙江南部海域蓝圆鲹生长异质性及死亡特征

蓝圆鲹（Decapterus maruadsi）属暖水性中上层鱼类,是中国近海重要的渔业资源。本文根据2015-2018年浙江南部海域（120.5°E~123.5°E,27°N~29°N）底拖网季度调查数据,运用线性混合效应模型等方法,研究了蓝圆鲹的叉长-体重关系和生长异质性,并估算其自然死亡系数。结果显示,蓝圆鲹样本叉长（L）范围为45.0~247.0 mm,平均叉长为126.1 mm;体重（W）范围为0.7~206.6 g,平均体重为29.1 g;叉长-体重关系式为：W=5.01×10^-6L^3.17。线性混合效应模型结果显示,同时考虑季节、性别和年份差异的模型对蓝圆鲹叉长-体重关系的拟合效果最佳。在相同叉长条件下,体重在秋季最大,其次是春季,而夏季最小;从不同年份来看,体重在2018年最大,其次是2016年,在2017年最小;从不同性别来看,雄性和雌性的差异不明显。这说明时间因素对于浙江南部海域蓝圆鲹的生长特征具有显著影响,2018年秋季蓝圆鲹的长势最佳。依据"Pauly"、"Pauly update"、"Jensen"、"Hoenig"和"Lorenzen"等不同的经验方程估算的蓝圆鲹自然死亡系数在0.36~1.41之间。本研究通过混合效应模型分析了年份、季节、性别对蓝圆鲹叉长-体重的影响,这对蓝圆鲹生活史特征及资源评估具有重要的参考意义。

Growth heterogeneity and natural mortality of Japanese scad in offshore waters of southern Zhejiang

Japanese scad (Decapterus maruadsi), a warm water pelagic fish, is an important economic species in China. Based on a quarterly bottom trawl survey in offshore waters of southern Zhejiang from 2015 to 2018, this study explored the length-weight relationships, growth heterogeneity, and natural mortality of Japanese scad. A total of 1,134 individuals were measured, with fork length (L) ranging from 45.0 to 247.0 mm and body weight (W) ranging from 0.7 to 206.6 g. The length-weight relationship was revealed to be W=5.01×10^-6L^3.17 for Japanese scad in the inshore waters of southern Zhejiang. A linear mixed effect model considering the random effects from season, gender, and year performed the best, with the lowest AIC and RMSE values. Results from the best model indicated that 1) individuals collected in the autumn tended to gain more weight than those collected in spring and summer at the same length; 2) individuals collected in 2018 grew with better condition, whereas those in 2017 and 2018 gained less weight at the same length; 3) there was no substantial differences between female and male Japanese scad. Therefore, year and season significantly influenced Japanese scad growth in the inshore waters of southern Zhejiang with the best growth condition in autumn 2018. Based on several empirical equations including Pauly, Pauly update, Jensen, Hoenig and Lorenzen methods, this study estimated the natural mortality for Japanese scad, which ranged from 0.36 to 1.41. This study exhibited that season and year significantly influenced the length-weight relationships of Japanese scad and the results could provide important information and knowledge for further study and fishery management for this important species in the coast waters of China.