雅鲁藏布江异齿裂腹鱼生活史对策和种群资源利用现状

LIFE HISTORY PATTERN AND EXPLOITATION STATUS OF A POPULATION OF SCHIZOTHORAX O'CONNORI IN THE YARLUNG ZANGBO RIVER

2008年8月至2009年8月在西藏雅鲁藏布江中游采集到异齿裂腹鱼(Schizothorax oconnori)1 126尾,对其生活史对策和种群资源利用现状进行了研究。结果显示:异齿裂腹鱼的总死亡系数(Z)雌性为0.090/a,雄性为0.112/a;自然死亡系数(M)雌雄分别为0.053/a和0.064/a;捕捞死亡系数(F)雌雄分别为0.037/a和0.048/a;开发率(E)雌雄分别为0.415/a和0.428/a。以达氏鳇(Huso dauncus)和尖头塘鳢(Eleotris oxycephaoa)作为参照物,运用模糊聚类进行分析,表明异齿裂腹鱼属于比较典型的K-选择类型鱼类。在现捕捞死亡系数、现起捕年龄和现自然死亡系数下,异齿裂腹鱼的繁殖潜力比雌雄分别为52.80%和51.64%,都大于目标参考点40%。通过单位补充量亲鱼生物量模型分析,显示目前雅鲁藏布江中游异齿裂腹鱼种群资源的开发水平较为合理。

Schizothorax o′connori （Cyprinidae：Schizothoracinae） is an endemic and commercial fish in the Tibetan Plateau,and only distributes in the middle and upper reaches of the Yarlung Zangbo River and its tributaries at elevations above 3000 m.This work estimated the life-history pattern and exploitation status of S.o′connori in the middle Yarlung Zangbo River,also evaluated the influences of fishing intensity and the age of first capture on spawning potential of the fish.The life history pattern and exploitation status of the fish were studied by examining 1126 individuals collected from August 2008 to August 2009 in the middle Yarlung Zangbo River,Tibet.The total mortality （Z）,natural mortality （M）,fishing mortality （F） and exploitation ratio （E） of S.o′connori were estimated with some classical formulae.A typical K-selected species Huso dauncus and a typical r-selected species Eleotris oxycephaoa were taken as references using a fuzzy cluster analysis,to evaluate the life-history pattern of S.o′connori by seven lifehistory parameters.The exploitation status of S.o′connori in the middle Yarlung Zangbo River was assessed using the spawning stock biomass per recruit model.Due to the uncertainty of natural mortality,we simulated the population dynamic variation under different M （female：0.053 ＆#177; 0.020/a; male：0.064 ＆#177; 0.020/a） in this study.The influences of fishing intensity and the age of first capture （tc） on spawning potential of the fish were also evaluated.The total mortality of S.o′connori was 0.090/a for females and 0.112/a for males.The natural mortality was 0.053/a for females and 0.064/ a for males,and fishing mortality was 0.037/a for females and 0.048/a for males.The exploitation level of S.o′connori was 0.415/a for females and 0.428/a for males.The fuzzy cluster analysis indicated that the life-history pattern of S.o′connori belonged to K-selection.At the current F,M and tc,the spawning potential ratio was 52.80% for females,and 51.64% for males,both higher than the target reference point 40%.Under three different M,the fishing mortalities of females and males were all lower than the target reference point 40%.It was concluded that the resource of S.o′connori in the middle Yarlung Zangbo River had been exploited reasonably,the population recruitment was sufficient,and this population could provide optimal yield under a stable status.However,if the fishing intensity increased continuously,once exceeded the threshold reference point F25% （0.091/a for females and 0.113/a for males）,the population might face with over-exploitation,and the recruitment pattern could not maintain the population equilibrium,and finally would be very easily depleted.High level of F beginning at late age could have the same effect on spawning stock biomass per recruit as lower F level applied at earlier age.Therefore,the catch per unit effort could be enlarged by rising tc in the long run.In addition,the small-size fish nets （especially trap nets） should be banned to prevent fishing of the young,and the highly destructive electrofishing must be resolutely banned.