臺灣鮭魚不是櫻鮭家族的一個地域族群－計數形質的證據

Formosa landlocked salmon (Oncorhynchus masou formosanus) is not a local population of cherry salmon complex-evidence from meristic characters

張詠政(Yung-Cheng Chang) ； 郭金泉(Jin-Chywan Gwo)

《國立臺灣博物館學刊》 62卷4期 (2009/12) Pp. 13-30

摘要

臺灣鮭魚(Oncorhynchus masou formosanus) (或稱櫻花鉤吻鮭、臺灣鱒、梨山鱒)是冰河平遺物種，屬太平洋鮭屬(Oncorhynchus)櫻鮭家族(Oncorhynchus masou complex)，目前全球僅分布和棲息於臺灣大甲溪上游七家灣溪少數河段。近來分子生物學証實其確為櫻鮭家族下之一亞種(Gwo et ai., 2008)，但為了確認臺灣鮭魚與其它櫻鮭家族在形態上是否有差異，並驗證早期日本文獻和臺灣先前研究者之記載，我們以更精準的X光和骨骼雙重染色兩方法，對四個櫻鮭亞種(琵琶鮭、櫻鮭山女魚、石川鮭、臺灣鮭)重新進行形態學之計數形質的研究。我們發現臺灣鮭魚與其他三個櫻鮭亞種在兩個計數形質(臀鰭與脊椎骨)有顯著差異(p≦ 0.001)，而且臺灣鮭魚均為計數形質數目最少的一亞種。根據Mayr & Ashlock (1991)於Principles of Systematic Zoology一書75 percent rule的定義，臺灣鮭魚是櫻鮭家族的一個亞種，而非日本櫻鮭的一個地理族群(cline：生態群，地域群)。此外，本研究亦發現21尾(23.1%)人工養殖的臺灣鮭魚樣本有尾端脊椎骨上下彎曲與鰭條異常的現象，究竟是族群過度近交或其他原因所致，尚待進一步調查。

並列摘要

The taxonomic status of Formosa landlocked salmon in Taiwan is debatable. In this study, three meristic characters (numbers of vertebrae, dorsal fin rays, and anal fin rays) were compared among three recognized species of cherry salmon complex (Oncorhynchus masou complex): masu (Oncorhynchus masou masou), Amago (Oncorh ynchus masou ishikawae), Biwa (Oncorhynchus masou subsp.) and specimens of Formosa landlocked salmon. A total of 196 specimens were examined. Their vertebral number, dorsal and anal fin rays were counted. Taiwan specimens, referred to as Formosa landlocked salmon, were shown to be a distinct subspecies distinguished from the masu, Amago and Biwa salmon from Japan using meristic counts. The X-ray radiography is very useful in determining meristic characters especially fin rays and vertebrae. It is simple, objective, non-invasive, and more precise than the previou sly used dissection method. In addition, it is fast and inexpensive. Vertebrae counting is proven to be an unambiguous diagnostic feature for subspecies assignment in Oncorhynchus masou specIes.