Decadal change in biological traits of Collichthys lucidus in Pearl River Estuary

Based on Collichthy lucidus samples collected in the Pearl River Estuary during January to April of 1986−1987, January to February of 2018 and March to April of 2019, we analyzed the decadal change in biological traits of C. lucidus including population structure, growth, feeding grade and so on. The results show the dominant body length group was 90−110 mm, and the average body length was (95±13) mm and (93±18) mm. There was no significant difference in the average body length between the two decades (P>0.05), but the proportion of individuals in the dominant body length group decreased (P<0.05). The body length of 50% sexual maturity was significantly shortened. From 1986 to 1987, the length of the first sexual maturity of the female population was 112 mm, but from 2018 to 2019, it was shortened to 88 mm. The fatness, feeding grade and proportion of males in the spawning population showed an upward trend. During 2018−2019, the average fatness and average feeding grade of the population, female and male were higher than those in 1986−1987 (P<0.05). From 1986 to 1987, there was a significant difference in the average feeding grade between male and female individuals (P<0.05), but no significant difference in the average feeding grade between spring and winter (P>0.05) and in the average fatness (P>0.05). From 2018 to 2019, there were significant differences in the average fatness and average feeding grade between male and female individuals (P<0.05), as well as in the average feeding grade between spring and winter, and the average feeding grade in winter was higher than that in spring (P<0.05).