印度洋中西部水域黄鳍金枪鱼的食性及其季节性变化

根据2003年12月至2004年6月及2005年9月至12月在印度洋中西部水域调查所获得的数据,利用两因子列联表及单因子方差分析等统计分析方法,对印度洋中西部水域黄鳍金枪鱼的食物组成及其随月份和体长的变化、摄食强度及食物组成的生态位宽度进行了初步研究.结果表明,印度洋中西部水域黄鳍金枪鱼食物组成包括帆蜥、鲣、鳞鲍、沙丁鱼、鲐鱼、虾、蟹、鱿鱼、章鱼、竹笑鱼及未辨认甲壳类等饵料类群,其中主要食物为鱿鱼、鲐鱼以及蟹.大部分月份黄鳍金枪鱼摄食率相对较高,基本上维持在70%以上;除2月和6月外,其余月份黄鳍金枪鱼饵料种类数更替率均低于50%.各叉长组黄鳍金枪鱼摄食率基本维持在70%以上;当叉长在106～155 cm之间,饵料种类数更替率低于40%.黄鳍金枪鱼摄食强度各月差异显著,但各叉长组摄食强度并不存在显著性差异.各月饱满指数存在显著性差异.黄鳍金枪鱼的食物组成随月份和叉长有明显变化.鱿鱼、鲐鱼和蟹基本上为不同叉长组黄鳍金枪鱼所摄食.黄鳍金枪鱼食物组成各月Shannon-Weiner多样性指数H'波动较大,且存在显著性差异;Pielou均匀度指数J'基本上维持在0.80～1.00之间,但各月间存在显著性差异.印度洋中西部水域黄鳍金枪鱼各叉长组食物组成Shannon-Weiner多样性指数H'变化较大,但在106～145 cm期间相对保持稳定,而Pielou均匀度指数J'波动较大.印度洋中西部黄鳍金枪鱼食物组成各月和各叉长组均存在显著性差异.

Feeding habits of Thunnus albacares in the west-central Indian Ocean

Based on the data collected by National Tuna Scientific Observer's Program in the west-central Indian Ocean during December 2003 to June 2004 and September to December 2005, the paper preliminarily analyzed diet composition and its variation over months and fork length, feeding intensity and food items'niche breadth of yellowfin tuna Thunnus albacares by using the two-way contingency table test and one-way Analysis of Variance. The results indicated that diet compositions of T. albacares included Alepisaurus, Scomber, Nautilus, Katsuwonus pelamis, Sardinaa, Octopus, Trachurus, shrimp, crab, squid and other fishes, with squid, Scomber and crab as the main diet item according to the percentage of occurrence. Over 70% of ingestion rates for all fork length classes of T. albacares sampled were found during most months of a year. Food item replacement rates of T. albacares were below 50% year round excluding February and June and below 40% for 106-155 cm fork length class. Significant difference in feeding intensity of T. albacares appeared between months, but non-significant difference occurred among the fork length classes. Significant difference also indicated between monthly stomach fullness indexes. Significant changes in diet compositions of T. albacares were found among both months and fork length classes. Squid, Scomber, and Mautilus were fed as the main food by all fork length classes T. albacares. Monthly Shannon-Weiner diversity index of diet composition of T. albacares varied greatly and significant T. albacares maintained at the level of 0.80-1.00 and asignificant difference between the indexes appeared. Big variation of Shannon-Weiner diversity index of diet composition of T. albacares occurred to all fork length classes. Significant differences can be found in Shannon-Weiner diversity index and Pielou's evenness index of diet composition of T. albacares among both months and fork length classes. It is the first time for our Chinese scientists to attempt the feeding habits analysis of T. albacares in the western and central Indian Ocean due to the limitation of sample size, sampling period (less than one year) and lack of experience in identifying food items, the authors only focused on the feeding habits analysis of T. albacares in the western and central Indian Ocean in preliminary way, further research should be carried out on the position of T. albacares in the marine ecosystem and the food relations between T. albacares and other tuna species and pelagic species.