| Summary: | 碩士 === 國立臺灣大學 === 漁業科學研究所 === 106 === Regarding the collapsing aquaculture industry of eel resulted from the shortage of Japanese eel (Anguilla japonica), tropical eel (Anguilla bicolor pacifica) becomes an alternative species for aquaculture. However, few studies have been investigated in the early life history of A. bicolor pacifica. Therefore, the aim of this study is to further expand the knowledge about the early life trait of A. bicolor pacifica.
In literature, if the glass eels are captured along the route of ocean currents, the farther from the spawning site, the longer the larval duration (LD) will be. In this study, the otolith microstructure of A. bicolor pacifica glass eels collected in Yilan (Taiwan), General Santos and Cotabato (Mindanao Island) was investigated to elucidate the early life history of A. bicolor pacifica in the Philippines by analyzing their total length (TL), LD, age at capture and growth rate. To contribute integral information and in-depth research in the analysis of otolith, previous data collected by other researchers in Yilan (Taiwan), Mati (Mindanao Island), Cagayan and Baler (Luzon Island) and Dumoga (Sulaweisi) are included.
Here, we found that the TL of the glass eels did not significantly differ among 6 estuaries, and that the relationship between the TL and the LD of glass eels was not significantly related, suggesting that larvae undergo metamorphosis when reaching a certain body length. Meanwhile, the age at capture and the LD presented significant positive relationship, indicating that the larvae with earlier metamorphosis recruit to their freshwater habitats faster than those which enter the metamorphosis afterwards. The captured glass eels along the routes of ocean currents exhibited a geographical cline in summer, with a longer LD farther from the spawning site, except for samples collected in Cotabato, while samples collected in Cotabato, Dumoga and General Santos in winter had a significant shorter LD and a faster growth rate. Considering the current speed, the distance and the growth rate, glass eels recruiting to General Santos are more likely to originate from two spawning sites: the NEC in summer and the Celebes Sea in winter, wherein the Celebes Sea may also be the spawning sites of glass eels collected in Cotabato and Dumoga.
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