Heterogeneity of fork length-weight relationship for juvenile Engraulis japonius based on linear mixed-effects models

Abstract

In order to examine the growth heterogeneity of juvenile Engraulis japonicus, we conducted heterogeneity analysis of fork length-weight relationships of the species based on the samples of juvenile E. japonius from April to June 2019 collected from the coastal waters of Zhejiang Province by using the generalized linear model and 9 linear mixed-effect models. The results showed that the fork length of juvenile E. japonius was between 14-74 mm, with an average of 33 mm. The dominant fork length group was 21-50 mm. The weight range was 0.01-2.96 g, with an average of 0.28 g, and the dominant body weight group was 0.01-0.50 g. According to Akaike information criterion (AIC), the growth-fitting model with both months and regions random effects on the growth parameters a and b of juvenile E. japonius fitted best.The reliable prediction results was testified by the cross-validation. In the best model, the fixed value of growth parameter a was 0.24×10-5 and its estimated value did not fluctuate significantly, while the fixed value of b was 3.246 and the estimated value ranged from 3.206 to 3.272, indicating that juvenile E. japonius was under positive allometric growth. Our results suggested that month and region significantly affected the fork length-weight relationships of juvenile E. japonius.