金沙江中下游细鳞裂腹鱼的年龄生长及种群动态

探究金沙江中下游细鳞裂腹鱼(Schizothorax chong)的年龄、生长及种群动态,可为其资源保护提供理论依据。2013-2017年在金沙江中下游干流攀枝花、巧家及其支流雅砻江、黑水河下游江段采集细鳞裂腹鱼170尾,逐尾测量全长、体长、体重,取臀鳞与微耳石为年龄鉴定材料,研究细鳞裂腹鱼的年龄结构、生长特征与种群动态。结果表明,金沙江中下游细鳞裂腹鱼以低龄个体(1~3龄)为主,臀鳞及耳石均能够作为其低龄个体的年龄鉴定材料;细鳞裂腹鱼体重(W)和体长(L)关系式为W=7.00×10^-6L^3.1885(R²=0.9867,n=170),雌雄个体间体长-体重关系无显著性差异(P>0.05);渐进体长(L_∞)为774.74 mm,生长系数(k)为0.13,理论生长起点年龄(t 0)为-0.13龄;渐进体重(W∞)为11407.01 g,体长生长方程为L_t=774.741-e^-0.13(t+0.13)],体重生长方程为W_t=11407.011-e^-0.13(t+0.13)^]3.1885,拐点年龄为8.79龄;种群总死亡系数(Z)为0.82,自然死亡系数(M)为0.26,当前开发率(E)为0.68,高于理论最大开发率(E_max)0.388;相对单位补充渔获量和生物量的结果也表现为过度捕捞特征,种群已处于过度利用状况。针对细鳞裂腹鱼的生态习性特征及其资源现状,建议采取生态调度、支流栖息地恢复及控制非法电捕等措施以保护其资源。

Age Structure, Growth Characteristics and Population Dynamic of Schizothorax chongi in Middle and Lower Jinsha River

Schizothorax chongi,belonging to Cyprinidae,Subfamily Schizothoracinae,Genus Schizothorax,is one of the important fish species endemic to the upper reaches of the Yangtze River.In this study,the age structure,growth characteristics and population dynamics of S.chongi were analyzed,based on the field investigation in Panzhihua and Qiaojia sections and two tributaries(Yalong River and Heishui River)of the middle and lower Jinsha River from 2013 to 2017.The objective was to understand the status of fishery resources in the district,and provide basic biological data and a theoretical basis for resource conservation.The field investigation was carried out in summer(June-August)and winter(November-December)during 2013-2017,with each survey lasting 15-20 d.The total length,body length and weight of each specimen were measured,and anal scales and otolith of each specimen were sampled for age determination.A total of 170 S.chongi specimens were collected during the investigation,with a body length range of 74-434 mm and body weight range of 8.2-1628.2 g.Using anal scales and otoliths as age identification materials,the S.Chongi sample population ranged in age from 1 to 5 years and was dominated by individuals of 1-3 years.The relationship between body length and weight was described as W=7.00×10^-6 L^3.1885(R²=0.9867,n=170)and there was no significant difference in the relationship between males and females.The asymptotic body length was L_∞=774.74 mm,the growth coefficient k was 0.13,the theoretical growth starting at age t0 was-0.13,and the progressive body weight W∞was 11407.01 g.The growth equations for body length and body weight were as follows:L_t=774.741-e^-0.13(t+0.13)]and W_t=11407.011-e^-0.13(t+0.13)^]3.1885,and the growth inflection point was 8.79 years.The total mortality coefficient Z was 0.82,and the natural mortality coefficient M was 0.26.The current exploitation rate(E)of this population was 0.68,higher than the theoretical maximum exploitation rate(E_max=0.38).The results of relative unit catch and biomass supplementation were characterized by overfishing,indicating a status of over-exploitation for S.chongi in the study area.In view of the ecological characteristics and resource status of S.chongi,we recommend that steps be taken to protect the species,including ecological regulation,restoration of tributary habitats and control of illegal electric fishing.