东太平洋公海大青鲨的胃含物组成研究

Composition of stomach content of blue shark( Prionace glauca) in the tropical eastern Pacific Ocean

根据2011年10月~2013年12月期间金枪鱼延绳钓渔船海上兼捕采集的样品(雌性66尾、雄性81尾,未鉴定性别1尾),首次对东太平洋公海海域(25°S^15°N,175°E^105°W)的大青鲨(Prionace glauca)胃含物组成及其多样性进行了探究。结果表明,摄食强度以1级为主(68%),雌雄间无显著差异(χ2,df=4,P>0.1);胃含物种类组成结构,硬骨鱼类占最大比例(占57.3%),其次是头足类(其中鱿占总饵料数的97.9%),雌雄间无显著差异(χ~2检验,df=15,P>0.05),但个体间差异大,重叠率低。饵料总体多样性Shannon-Weiner指数(H)为1.78,Simpson指数(C)为0.28。随大青鲨叉长增加,H略呈下降趋势,C略呈上升趋势。成熟中、排卵中、已怀孕3个阶段的雌性个体饵料组成多样性略有差异。聚类分析显示,1月~3月、8月~10月和11月~12月的饵料组成结构中,8月~10月和11月~12月的相似性较高。

Based on the samples collected by tuna long-line fishery in the tropical waters of the eastern Pacific Ocean （25°S - 15°N, 175 °E - 105 °W） during October 2011 to December 2013, we analyzed the stomach content and prey diversity of blue shark （Prionace glauca）. The feeding intensity of blue shark was dominated by level one （68%）. The composition of feeding intensity between female and male was not significantly different （ χ^2 -test, P 〉 0. 1 ）. Teleosts were major prey items （ 57.3% ）, followed by cephalopods （97. 9% were squid）. The diet composition was not significantly different between female and male, but significantly different among individuals. The Shannon-Weiner diversity index （H） and Simpson diversity index （C） for prey items were 1.78 and 0.28, respectively. The index H decreased but index C increased with increasing blue shark size. The prey diversity indices for female blue sharks in maturing, ovulating and gravid stages were slightly different. Cluster analysis shows that the diet compositions of August - October and November - December were more similar than that of January - March.