Studies On The Feeding Habits Of Trichiurus Leptyrus In East China Sea

Fish feeding ecology is an important content of the fish ecology, the feeding of fishhas an important significance to maintain its growth and development. At the same time,the feeding behavior of fish will affect the composition of the prey communities. Fishfeeding habits study is essential for a rational utilization a management of fisheriesresources, it also can deepen our understanding of the ecosystem of fish and entireecosystems.Since21century, the resources of Trichiurus leptyrus has declined and the balanceability of Trichiurus leptyrus population has been upset due to the high-level fishing. Thefish catch of Trichiurus leptyrus has declined for4years and it slumped to the lowest leveluntil the year of2012. Based on the widespread sampling of Trichiurus leptyrus in EastChina Sea, stomach contents analysis were used to study the spatial and temporaldistribution of fish feeding habits of Trichiurus leptyrus and make an approach tocannibalism of Trichiurus leptyrus, to show Trichiurus leptyrus change their feeding habitswith the regional variation, seasonal variations, diurnal variation and ontogenetic. It willdeepen our understanding of the feeding intensity and the composition of food organismswhich can provide a scientific evidence and theoretical foundation for protecting the uniquefish resources and making a further study of the fish physiology, fish breeding and fishfarming. At the same time, it also can promoted our investigation and study of marine fishfeeding ecology. The main results are as follows:We found that there are at least84genus of food organisms in the food composition ofTrichiurus leptyrus by stomach contents analysis, according to the proportion of foodorganisms in the stomach contents we found that Trichiurus leptyrus is mainly feeding onfish, macrura, amphipoda, brachyura and cephalopoda, at the same time, they are alsofeeding on euphausia, ostracods and eggs. According to different ecological groups oforganisms, bait of Trichiurus leptyrus can be divided into three ecological groups whichcontain zooplankton, benthos and nekton.Trichiurus leptyru have different feeding habit in different stages of their growth anddevelopment. Their feeding intensity is the highest in the size class of251-445mm while the lowest in the size class of151-200mm; the diet composition varied in different with fishsize, the frequency of fish increased significantly with the increase of fish size, whereas thefrequency of amphipodas decreased. The feeding habit varied significantly with thevariation, the feeding intensity, as indicated by the percentage of empty stomachs(PES) andmean stomach fullness index(MSFI), varied significantly among seasons. The feedingactivity was the highest in autumn while the lowest in summer; the diet composition alsovaried among seasons, the types of diet food were the most in summer, followed by springand autumn,the least in winter. Richiurus leptyrus changed their feeding habits with diurnalvariation, the feeding intensity varied significantly with diurnal variation, the minimumvalue of MSFI occurred between22:00p.m. and02:00a.m. showed that the feedingactivity is the lowest in this period; there are37types of diet food in the period of18:00-22:00while only20types in the period of22:00-02:00.The feeding habits ofTrichiurus leptyru also varied with the regional variation. The feeding intensity was thehighest in the southern part of East China Sea, while in the northern part of East China Seawere the lowest. Compared whit historical data, the feeding habits of Trichiurus leptyruvaried significantly, the proportion of Euphausia sp. Decreased markedly while fishincreased evidently, in addition, high intensity of cannibalism was also shown.