Feeding ecology and trophic dynamics of skipjack tuna (Katsuwonus pelamis) in eastern Taiwan.

• Main Authors: Chiang, Ching-Lung, 江慶龍
• Other Authors: Wang, Sheng-Ping
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/jja2gr

碩士 === 國立臺灣海洋大學 === 環境生物與漁業科學學系 === 102 === Skipjack (Katsuwonus pelamis) tuna are highly migratory fish which play a major role in the pelagic marine ecosystem as predators of epipelagic and mesopelagic organisms. The objective of this study was to investigate the food habits and trophic niche of skipjack tuna in eastern Taiwan waters. We analyzed stomach contents and stable isotopes analysis of 347 specimens collected from the Shinkang fish market in Taitung during September 2012 to February 2014. Fork length and body weight of the specimens ranged from 34.5 to 79.5 cm and 0.6 to 10 kg, respectively. The indices of individual prey including percentage of number, mass and frequency of occurrence, and index of relative importance (IRI) were calculated. Based on non-empty stomachs (48.5%), cephalopods, epipelagic fishes and crustaceans were predominantly preys. IRI of inshore squids (Loligo sp.) was highest followed by sand lances (Ammodytidae sp.) and linxia (Euphausiidae sp.). In aspects of stable isotopes, males and females showed similar diet preferences with a high diet overlap and similar values ofδ13C andδ15N. The stable isotope values in different oceans indicate different productivity, and in the study, the stable isotope values of top predators reveal the different primary productivity in different oceans. The mean trophic level estimated in this study by the two methods was around 3.3(SD=0.59), indicating that this species is a high-ranking predator in the eastern Taiwan waters. Stomach contents analysis and stable isotopes analysis will be performed for skipjack and their prey and the results will provide longer-term behavior of skipjack diet in the northwestern Pacific Ocean.