Reproductive biology of Coilia nasus in the Oujiang River Estuary
To understand the reproductive biology of Coilia nasus in the Oujiang River Estuary,311 samples of C.nasus were collected from May to August 2021,and biological characteristics such as body length,body weight,sex ratio,gonadal maturity,relative condition factor(Kn),gonadal index(GSI),and fecundity were analyzed.The results showed that the body length of C.nasus ranged from 121 mm to 330 mm,and the dominant body length group ranged from 220 mm to 300 mm,accounting for 61.74％of the total,and the average body length was(235.0±47.8)mm.The body weight of C.nasus ranged from 6.0 g to 197.0 g,and the dominant body weight group ranged from 6.0 to 120.0 g,accounting for about 92.28％,and the average body weight was(63.6±38.7)g.The relationship between body length and body weight was W=5.77×10-7L3.362 5(R2=0.973 2),b＞3,indicating that C.nasus was growing at an anisotropic rate,and the growth index of different sexes showed bfemale＞bmale.The ratio of females to males among all sexes identified was 2.5∶1,and females were dominant in different months.There were differences in the composition of gonadal maturity of females in different months,with stage Ⅱ ovarian development predominating in May and August,stages Ⅴ and Ⅲ in June,and stages Ⅱ and Ⅲ in July.The absolute fecundity F of the reproductive population of C.nasus ranged from 11 890 to 57 843 grains,with a mean value of(31 388±9750)grains;the relative fecundity FL of body length ranged from 47 grains·mm-1 to 192 grains·mm-1,with an average value of(109±31)grains·mm-1;the relative fecundity FW of body weight ranged from 158 grains·g-1 to 456 grains·g-1,with an average of(281±68)grains·g-1.The oocyte diameter of C.nasus ranged from 0.40 mm to 0.98 mm,with an average value of(0.73±0.08)mm,and the dominant group was 0.60-0.80 mm,accounting for 91.8％of the total.The values of relative condition factor(Kn)in different body length groups and different months were close to or greater than 1,indicating that the physiological condition of C.nasus in the Oujiang River Estuary was in a stable state during the breeding period.The size of C.nasus differed in different months,among which the body length in May was larger than that in June,July and August,probably because larger size individuals had more abundant energy reserves and were the first to conduct reproductive migration.The GSI reached the maximum value in June and began to decline in July,indicating that June was the peak reproductive period.The absolute fecundity of C.nasus was correlated with body length,body weight and ovarian weight in a power function,and the correlation with ovarian weight was the highest.The body length of female Coilia nasus at first sexual maturation(L50)was estimated to be 236.8 mm by fitting of logistic equation.The study enriches the biological materials on Coilia nasus in the Oujiang River Estuany,and can provide basic data support for the further evalution of fishing ban,and policy-making for the conservation and management of Coilia nasus resources.
Coilia nasusOujiang River Estuaryfecunditybiological characteristicssize at first maturity
万方数据
维普
