Abstract: In order to understand the growth dynamics of Larimichthys polyactis in spring and autumn along the coast of Zhejiang Province, we used the survey data of bottom trawlers in spring (April) and autumn (November) from 2014 to 2019 along the coast of Zhejiang Province to examine the heterogeneity of L. polyactis growth by constructing a generalized linear model (GLM) and nine linear mixed effect models (LMEM). The results showed that body length of L. polyactis ranged from 15 mm to 210 mm, with an average of 124.12 mm. The dominant body length group ranged from 110 mm to 140 mm. The body weight ranged from 0.04 g to 156.2 g, with an average of 33.28 g. The dominant body weight group ranged from 30 to 50 g. According to the AIC minimum criterion, the LMEM model with the random effects of seasons and water zones on growth parameters a and b was the best. The results of cross validation also showed that the prediction of this model was the best. In the optimal model, the fixed value of growth parameter a was 0.61×10^-4, which ranged in (0.32-1.91)×10^-4 after adding season and water random effect. The fixed value of parameter b was 2.73, and ranged from 2.49 to 2.86 after adding the random effects of season and water area, indicating that small yellow croaker was under negative allometric growth. Season and water zone had significant effects on the relationship between body length and body weight of small yellow croaker. From a seasonal perspective, the growth rate of small yellow croaker in spring was higher than that in autumn. From water zone perspective, the closer the offshore distance, the faster the growth rate of small yellow croaker.

Key words: Larimichthys polyactis, linear mixed-effects model, body length-weight relationship, growth, heterogeneity