The stomachs of 183 bigeye tuna (Thunnus obesus) were collected from three Taiwanese longline vessels operating in the western Indian Ocean during the period from April to December 2006. Their fork lengths ranged from 89 cm to 198 cm. Distinguishable prey species, belonging to 28 families, consisted mostly of fishes, crustaceans, and cephalopods. Fourteen prey items were newly recorded, among them, five families (Anoplogastridae, Bothidae, Grammicolepididae, Pinguipedidae, and Sciaenidae) were firstly recorded as the diet of bigeye tuna. Two special dietary species were found for the first time. Oplophorus gracilirostris, the dominant numerical dietary species, had not been previously recorded; however, O. typus had been recorded in the past. The other special prey species found, Macrurocyttus acanthopodus (Grammicolepididae), was not only the first record in the stomach of bigeye tuna but also the first record in the Indian Ocean. The largest body length among prey species was 655 mm for an Alepisaurus ferox. The number of prey species appeared to decrease with the increasing size of the bigeye tuna, and larger Indian bigeye tuna tended to feed on larger prey species. In the stomachs of the bigeye tuna, Oplophorus gracilirostris was the most frequently found prey species (56.8%). The three numerical most dominant prey species were Oplophorus gracilirostris (38.2%), Charybdis smithii (8.8%), and Alepisaurus ferox (3.6%). In addition, the fish prey item, Alepisaurus ferox, had the highest percentage of prey weight. The total percentage of prey weight for prey fishes is similar to that reported in previous research, but the average weight of Alepisaurus ferox is heavier than the previous report. Additionally, the percentage of prey weight for Paralepididae is lower than the results of previous studies. Moreover, the occurrence and percentage of the number of Oplophorus gracilirostris are distinctly higher than the results of previous studies. These findings indicate that the percentage of mean preys number exist seasonal effect. Alepisaurus ferox was the most numerous prey in May to July; Oplophorus gracilirostris was the most numerous prey at 200 m depth in August to October 45¢XE to east; Charybdis smithii was the most numerous prey at 50 m depth in August to October 45¢XE to west. A possible reason to explain this phenomenon is that there are strong feeding migratory behavior in bigeye tuna.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0911112-230126 |
| Date | 11 September 2012 |
| Creators | Lin, Jing-siang |
| Contributors | Chih-Wei Chang, Chiee-Young Chen, Wann-Duen Chiou, Chien-Chung Hsu, Meng-Hsien Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0911112-230126 |
| Rights | user_define, Copyright information available at source archive |
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