沱江史家段四川华吸鳅个体生殖力研究

Individual Fecundity of Sinogastromyzon szechuanensis in Shijia Section of Tuojiang River

为了解沱江史家段四川华吸鳅(Sinogastromyzon szechuanensis)的个体生殖力,于2018年3-5月采集性腺发育到IV期的雌性个体83尾,测量所有样本的体长(L)、体重(M)、净体重(W)、卵巢重(W_(a)),并计算成熟系数(GSI)和丰满度(K);取鳞片鉴定年龄,测定卵粒直径,通过重量法计数个体绝对生殖力(F)、体长相对生殖力(F_(L))以及体重相对生殖力(F_(W)),用5种数学模型及回归方程拟合个体生殖力与形态指标的关系。结果显示,调查样本由2、3、4龄组成,分别占繁殖群体总数的26.51%、50.60%、20.89%;繁殖群体优势体长组为50.0-70.0 mm(n=59),占总数的71.08%;优势体重组为3.01-5.00 g(n=31),占总数的37.35%。F为(829.09±627.54)粒,变幅80-3790粒;F_(L)为(12.95±8.46)粒/mm,变幅1.40-48.58粒/mm;F_(W)为(206.97±114.73)粒/g,变幅25.21-614.45粒/g。F和F_(L)与体长、体重、净体重、成熟系数和年龄,F_(W)与体长、成熟系数和年龄呈二次函数相关;多元逐步回归分析发现,绝对生殖力、体长相对生殖力与成熟系数和体长呈正相关,回归方程分别为F=-163.533+82.148 GSI+78.691L(R^(2)=0.675,P<0.01),F_(L)=-1.866+1.195GSI+0.305L(R^(2)=0.646,P<0.01)。体重相对生殖力与成熟系数呈正相关,与体重呈负相关,回归方程为F_(W)=-0.590+17.177GSI-12.727W(R^(2)=0.639,P<0.01)。四川华吸鳅卵径分布只出现了一个较大的峰值,推测其为一次产卵类型。

Sinogastromyzon szechuanensis,endemic to the upper Yangtze River,is listed as an important conservation species in Sichuan Province.In this study,we explored the individual fecundity of S.szech⁃uanensis in Tuojiang River,including measurements of individual absolute fecundity(F),relative fecundity per millimeter(F_(L)),relative fecundity per gram(F_(W)),maturity coefficient(GSI)and condition factor(K).The relationship between measures of individual fecundity and morphological indices of the S.szechuanensis was also analyzed.The objective was to better understand the reproductive ability of S.szechuanensis and provide theoretical evidence for germplasm resource conservation and artificial reproduction of S.szechuanensis.From March to May of 2018,a total of 83 female S.szechuanensis in ovary stageⅣwere collected from the Shijia section of Tuojiang River.The body length(L),body weight(M),net body weight(W),ovary weight(W_(a))and egg diameter of all specimens were measured.Age was determined using scale growth rings and F,F_(L) and F_(W) were determined by gravimetry.Results show that the specimens collected were 2,3 and 4 years old,respectively accounting for 26.51%,50.60%and 20.89%of the total number collected.The body length of most fish(71.08%)fell into the range of 50.0-70.0mm(n=59),and many(37.35%)had a body weight in the range of 3.01-5.00 g(n=31).The ranges of F,F_(W) and F_(L) were,respectively,80-3790 eggs,25.21-614.45 eggs per gram,1.40-48.58 eggs per mm,with an average value of(829.09±627.54)eggs,(206.97±114.73)eggs per gram and(12.95±8.46)eggs per mm.F and F_(L) increased with body length,body weight,net body weight,maturity coefficient and age(P<0.05).These two measures of fecundity initially increased with condition factor and then decreased(P>0.05).F_(W) increased with maturity coefficient(P<0.05),decreased as body length increased(P<0.05),decreased and then increased with net body weight and age(P<0.05),and did not correlate with body weight(P>0.05).F and F_(L) presented significant quadratic correlation with body length,body weight,net body weight,maturity coefficient and age,while F_(W) presented significant quadratic correlation with body length,maturity coefficient and age.Further,multivariate stepwise regression analysis showed that individual absolute fecundity,and relative fecundity by length were positively correlated with maturation coefficient and body length.The respective regression equations were F=-163.533+82.148GSI+78.691L(R^(2)=0.675,P<0.01)and F_(L)=-1.866+1.195GSI+0.305L(R^(2)=0.646,P<0.01).The relative fecundity by weight was positively correlated with maturity coefficient and negatively correlated with body weight,and the regression equation was F_(W)=-0.590+17.177GSI-12.727W(R^(2)=0.639,P<0.01).The distribution of egg diameters indicated that S.szechuanensis spawns once a year.These results provide valuable support for conserving S.szechuanensis populations.