| 英文摘要 |
Japanese eel is an important aquaculture species in Asia. Due to the unavailable commercial production of the glass eel by artificial propagation, abundant glass eels thus are caught in the estuary for aquaculture need, causing a serious problem of overfishing. In the shortage of eel resource, the competition for the glass eel is expected to become more and more serious in the future. Thus, monitor and manage the eel resource will be the key for the sustainability of eel aquaculture industry. In this study, we investigated the glass eel resource in Taiwan by monthly collecting them in the estuary of Danshui, Hualiang and Pingtong for 3 days during the new moon period. Samples are then species identified by morphometric and molecular methods. Besides, we collect the catch data of the Japanese glass eel from eel traders of Taiwan, Taiwan Fisheries Year Book, and a statistic department of the Japan Aquaculture News to analyze inter-annual patterns of glass eel catch, and try to establish the glass eel production model as well. For the catch and management study of the glass eel, we will interview eel fishermen, eel farmers and eel traders to establish a reasonable regulation for glass eels in Taiwan. The results indicate that there are four species Anguilla japonica, A. marmorata, A. bicolor pacifica and the newly reported species A. luzonensis in Taiwan. The recruitment of Japanese eel mainly in winter, A. marmorata have two peak recruitment in spring and summer, the number of A. bicolor pacifica increased slightly during the fall season, A. luzonensis has no clear recruitment season and is very rare in Taiwan. Danshui and Pingtong have a similar seasonal composition of glass eel, but the pattern in Hualiang is quite different and mainly A. marmorata. An analysis of data of the catch of glass eel indicated that the glass eel catch mainly fluctuates in a cycle of 5- 6 yr and have burst catches every 11 yr. The fluctuations may be related with the eel reproductive cycle and impact of the environment variation. In the catch and management study, the catch glass eel is mainly by boat net, and the fishing pressure is very high and no limitation of fishing area is performed. We suggest that the government should guide regulations for fishing boats by issuance the glass eel fishing license and ask them reporting the true catch amount. Catch season is suggested during November and February. In this way, eel conservation and resource monitoring can be looked after both sides. |