[Population characteristics of Collichthys lucidus in the Pearl River Estuary during 2017 and 2020]. / 2017­2020å¹´ç æ±Ÿå£æ£˜å¤´æ¢ ç«¥é±¼çš„ç§ç¾¤ç‰¹å¾.

ABSTRACT

To understand the population characteristics of Collichthys lucidus, an important economic fish in the Pearl River Estuary, the biological characteristics and resource density distribution characteristics of C. lucidus were preliminarily analyzed using bottom trawling by cruises conducted in each spring and autumn during 2017 and 2020. The results showed that the body length and weight of C. lucidus ranged between 22-168 mm and 0.23-103.11 g, respectively. Female individuals were larger than the male ones. The length of sexually mature individuals intensively ranged between 90 mm and 140 mm. Neither of them evidenced the earlier of sexually maturity nor the minimizer of dominant group. The population of C. lucidus in Pearl River estuary still developed in safe status in all, but its habitat downgraded than in 1988, as indicated by the fact that the allometric growth factor (b=2.9057) of the body length to body weight had no significant annual variations, but the conditional factor (a=3.029×10-5) was drama-tically decreased than in 1988. The population was at a state of overexploitation due to the estimated exploitation rate of 0.67. The resource density averaged 77.73 kg·km-2, showing a pattern of higher in the middle and west than in the east and relatively uniform of latitudinal distribution. The four high densities of sampling zones suggested that the zone around Nansha Port was probably the core of spawning ground of C. lucidus. Considering the annual average resource density in 2017-2020 sharply decreased by 93.5% than in 1980 to 1982, it was pressing to establish the protection zone in spawning ground in spring to protect the recruiting and spawning stocks of C. lucidus population.