利用生命條碼分析臺灣市售魚翅種類與其在漁業管理和物種保育上之應用

Abstract

魚翅是整尾鯊魚個體中經濟價值最高的部位，長久以來在東亞以及東南亞國家中食用魚翅的風氣相當盛行，在中國更是一項流傳了數百年的珍貴菜餚；本研究基於對軟骨魚類保育的觀念，欲探討台灣市售魚翅種類之組成。自國內各大漁港與都會區採樣或購買的魚翅，包括新鮮魚翅、乾製魚翅、水發魚翅、罐頭和調理包魚翅等，由於沒有完整的個體，難以靠形態鑑定種類，故採取分子生物學的方式，利用生命條碼鑑定所收集到的樣本；選用的 DNA 片段為粒線體 COI 基因。研究結果顯示，新鮮魚翅、乾製魚翅與水發魚翅皆能以此方法成功鑑定物種；但罐頭及調理包魚翅則未能成功放大所需之 DNA 片段。種類分析方面，在 1170 個樣本中，成功鑑定了 686 個，總共發現 46 個物種，分屬 8 目 14 科 21 屬。分析的樣本當中，數量最多的物種是鋸峰齒鮫，其次依序是平滑白眼鮫、灰鯖鮫、深海狐鮫、紅肉丫髻鮫和淺海狐鮫。保育狀況方面，本研究鑑定出之物種，根據國際自然保護聯盟的評估與分類，極危的物種佔了 2.2 %，瀕危的物種佔了 4.3 %，易危的物種佔了 32.6 %，近危的物種佔了 39.1 %，無危的物種佔了 15.2 %，數據缺乏的物種佔了 4.3 %，未評估的物種佔了 2.2 %。 除了種類鑑定之外，本研究亦分析了各 COI 序列之間的演化距離，結果顯示，各物種內的演化距離分布為 0.002-0.035，平均 0.007；屬內為 0.003-0.102，平均 0.029；科內為 0.003-0.105，平均 0.054。之後將本研究所採集而來的單倍型序列用以建構親緣關係樹，發現各物種在親緣關係樹中均能被分離開，因此證實了 COI 序列對於軟骨魚類的種類鑑定具有很好的效果。 最後，在針對八個受區域漁業管理組織規範的物種之親緣關係分析結果顯示，淺海狐鮫、狐鮫、平滑白眼鮫、紅肉丫髻鮫、丫髻鮫等五個物種在不同的洋區有遺傳分化之現象；深海狐鮫、污斑白眼鮫、八鰭丫髻鮫此三個物種則無。 經由本研究可得知，利用粒線體 COI 基因當作生命條碼分析市售魚翅為一快速、有效且準確的方法；此方法將在漁業管理以及保育工作上能夠起到很好的輔助效果。

Shark fin is the most valuable part in a whole shark body, the custom of eating shark fin is very popular in East and South-East Asia, and it has been counted a traditional noble delicacy in China for centuries. This study aims to analyze constitution of species in Taiwan market fins. We collected or purchased shark fin samples from fishing ports or metropolis in Taiwan, including fresh fin, dried fin, soaked fin, canned fin, and pack fin. Because of lacking key features, it is impossible to identify species of the samples by morphological method. We used the molecular tool- DNA barcode (the gene marker is mitochondrial COI gene) to accomplish it. The results showed that this method is appropriate in species identification of fresh fin, dried fin, and soaked fin, but inappropriate in canned fin and pack fin. In the results of species analysis, we found 46 species in the 686 successfully indentified samples of the all 1170 samples. The 46 species belong to 8 orders, 14 families, and 21 genera. In all the samples we analyzed, the most plentiful species is Blue shark, subsequently are Silky shark, Shortfin mako, Bigeye thresher, Scalloped hammerhead, and Pelagic thresher. In status of conservation, according to the evaluation and classification by IUCN, critically endangered species account for 2.2 %, endangered species account for 4.3 %, vulnerable species account for 32.6 %, near threatened species account for 39.1 %, least concern species account for 15.2 %, data deficient species account for 4.3 %, not evaluated species account for 2.2 % in all the species we found in this study. In addition to species identification, we also calculated evolutionary distances of the COI sequences. The results showed that within-species distances ranged from 0.002 to 0.035, with the mean value on 0.007; within-genus distances ranged from 0.003 to 0.102, with the mean value on 0.029; and within-family distances ranged from 0.003 to 0.105, with the mean value on 0.054. Furthermore, all the species can be perfectly separated in phylogenetic trees which are constructed by the haplotypes, it indicated that capability of COI gene in species identification of chondrichthians is very good. Moreover, phylogenetic analyses showed regional genetic divergences in Pelagic thresher, Thresher, Silky shark, Scalloped hammerhead, and Smooth hammerhead; but no divergence in Bigeye thresher, Oceanic whitetip shark, and Great hammerhead. We affirmed that using mitochondrial COI gene as a DNA barcode to identify chondrichthian species is a fast, effective, and accurate method, which will be helpful for fishery management and species conservation.