以耳石日周輪研究太平洋雙色鰻之早期生活史

Abstract

日本鰻 (Anguilla japonica) 2014年被國際自然保育聯盟 (IUCN) 列入瀕危物種，形成產業永續發展的瓶頸。為了減緩日本鰻的資源壓力，發展新的養殖物種相當重要。近幾年，東亞各國遂興起了異種鰻的養殖風潮，其中以鱸鰻 (A. marmorata) 以及太平洋雙色鰻 (A. bicolor pacifica) 之發展最受矚目。他們的鰻苗來源大多來自菲律賓。因此了解這些鰻苗的早期生活史，對於鰻鱺屬的資源管理與產業發展極有幫助。 根據前人的研究，雙色鰻可能產卵於馬里亞納海溝以西，柳葉鰻隨者洋流的漂送到菲律賓、台灣和印尼地區。本研究再利用耳石日周輪定齡之方法，來了解太平洋雙色鰻早期生活史特徵。收集了台灣、菲律賓呂宋島及民答那峨島和印尼北蘇拉維西的鰻線樣本。我們測試此假說:距離產卵場越遠，柳葉期越長，距離產卵場越近，則柳葉期越短。研究結果發現，北蘇拉維西地區的樣本平均柳葉期天數明顯小於其他地區。因此，推測太平洋雙色鰻極可能有一個以上的產卵場區域。

The Japanese eel (Anguilla japonica) was listed in the IUCN red list in 2014 as an endangered species, forming the bottle neck of sustainable eel aquaculture industry. To slow down the resource pressure of the Japanese eel, it is an important work to develop a new aquaculture species. In recent years, the culture of exotic eel species become more and more popular, especially on A. marmorata and A. bicolor pacifica. Their glass eels are mostly imported from the Philippines. Understanding the life history of these species is very helpful for the resource management as well as the industry development of the eels. According to previous studies, A. bicolor pacifica may spawn at west of the Mariana Islands and their leptocephali are transported by ocean currents to Taiwan, Philippines, and Sulawesi Island of Indonesia. Otolith microstructure of A. bicolor pacifica were examined in glass eels collected from Taiwan, Philippines, and Sulawesi Island of Indonesia. We test this hypothesis that the more away from the spawning ground for glass eel, the longer mean larval duration it would have. Our results find that Sulawesi has unusually shorter mean larval duration than other sampling sites. Hence, A. bicolor pacifica may have more than one spawning areas in the western north Pacific.