Reproductive biology and strategy of Megalobrama terminalis of Xijiang River

Abstract

Knowing fish reproductive strategy is essential for understanding population dynamics. This study intends to investigate the reproductive cycle, the timing of spawning, length at first maturity, fecundity type and fecundity of Megalobrama terminalis, one of the important commercial fishes in Xijiang River in order to illuminate adaptation of reproductive strategies of M. terminalis with human activity intensifies. The results indicated that the average body length of M. terminalis was 245 mm, dominated body length of fishes concentrated in the 260-280 mm range, while the average body weight of M. terminalis was 347 g, dominated body weight of fishes concentrated in the 320-480 g range. Length at first maturity was estimated as 244.5 and 232.2 mm for females and males, respectively. The ratio of females to males was 1.105 to 1, and with the increase of body length, the ratio of females to males showed a trend of decreasing first and then increasing. The spawning season was from April to August, and the spawning peak was from early June to early July, and the density of M. terminalis larvae had a close relationship with discharge. The average absolute fecundity of M. terminalis was 73069 oocytes, and the average relative fecundity was 118.7 oocytes/g gutted weight. The absolute fecundity was positively correlated with body length and body weight, while gonadosomatic index was closely related to gonadal weight, fatness and body weight. Under the influence of intensified human activities, the adaptive changes of the reproductive strategy of M. terminalis: primary sexual maturity length and the absolute fecundity decreased.