呂宋鰻在台灣及菲律賓的生物地理分佈

Abstract

鰻魚為東亞國家重要的養殖魚種之一，但近年鰻魚的資源量都在急速的下降，不論是鰻苗或是成鰻，數量都比以往來的少，而鰻魚養殖所需的鰻苗，完全都是從漁民捕撈而來，在資源量減少的情況下，物種復育、新養殖鰻種的興起甚至取代，都成為研究的目標之一，而呂宋鰻(A.luzonensis，又名黃氏鰻A.huangi)於2009年被公布為第19種鰻魚，然而此新鰻種雖然已被公布，但對於它的生物地理分布、資源量、生物特徵等相關的研究資料是少之又少，因此本篇想針對呂宋鰻的生物地理分布與生物形態特徵，建立完整的資料庫。 本篇的樣本來源分成兩個部分，以呂宋鰻被發現的時間(2008)做為分界點，第一部分是2008年至2011年，採自菲律賓、台灣、印尼採集之鰻苗，第二部分是1984年至2008年採自台灣之鰻苗。利用型態與DNA鑑定方法，鑑定出各採樣點之鰻苗組成，由此建立出呂宋鰻的生物特徵及生物地理分布。結果指出，呂宋鰻的高捕獲量主要出現在菲律賓呂宋島的7、8、9三個月，而在這三個月中，其數量甚至超過鱸鰻，而在台灣方面，呂宋鰻非常稀少，捕捉量8、9、10月較其他月份為高，印尼地區則無發現。生物形態特徵方面，鱸鰻及呂宋鰻的鰭差比分布圖之比較，可看出有少部分重疊的情況發生，而導致有可能誤判。呂宋鰻色素與體長的相關變化，從VA時期至VIA3時期呈現緩慢下降或是停滯，趨勢與日本鰻類似；月份與體長之比較，趨勢並不明顯且無規律。呂宋鰻的生物地理分布於本篇中確立出以菲律賓為主。

Eels have been an important category in aquaculture in East Asian countries. But in recent years the stock size of eels has been in rapid decline. No matter it is eel fry or adult eels, their quantities are much less than the past. All the eel fry needed in eel farming come totally from the catches by fishermen. Under the circumstance of reduced stock size, things like species rehabilitation, emergence of newly farmed eel species or replacement by new species have become one of the targets of the researchers. A. luzonensis, also known as A. huangi, has been announced as the 19th species in 2009. Although this new species has been announced, the relevant research information on its biogeographic distributions, stock size, and biological features is quite meager. As such, this paper aims at exploring the biogeographic distributions and early life history of A. luzonensis. Samples used in this paper are from two parts. The first part is collections of A. luzonensis from 2008 to 2010. The second part is collections of A. marmorata from 1984 to 2008. The demarcation is the time (2008) when A. luzonensis was discovered. Collections made after 2008 are mostly in places in the Philippines, Taiwan, and Indonesia. Prior to 2008, they were mainly collected in Taiwan. After that, pattern identification is employed to establish the biological features and biogeographic distributions of A. luzonensis. The results indicate that high catches of A. luzonensis are mainly in the three months of July, August, and September in the Philippines. In the three months the amount of A. luzonensis caught is even more than that of A. marmorata. In Taiwan, A. luzonensis is extremely rare and from September to January more catches are seen. As to Indonesia, there is no finding yet. In terms of biological patterns and features, we can see that there is an overlap that leads to possible misidentifications from the comparison of fin difference ratio in A. marmorata and A. luzonensis. The associated change of pigmentation of A. luzonensis and its total length shows resemblance in the run chart compared to that of A. japonica in that there is a slow downward slope or even a standstill from VA to VIA3 stages. The comparisons of months with total lengths showed no obvious upward or downward trend. In this paper we have established the biogeographic distributions of A. luzonensis in the Philippines primarily.