DNA Barcoding of Shark Meats Identify Species Composition and CITES-Listed Species from the Markets in Taiwan

BackgroundAn increasing awareness of the vulnerability of sharks to exploitation by shark finning has contributed to a growing concern about an unsustainable shark fishery. Taiwan’s fleet has the 4th largest shark catch in the world, accounting for almost 6% of the global figures. Revealing the diversity of sharks consumed by Taiwanese is important in designing conservation plans. However, fins make up less than 5% of the total body weight of a shark, and their bodies are sold as filets in the market, making it difficult or impossible to identify species using morphological traits.MethodsIn the present study, we adopted a DNA barcoding technique using a 391-bp fragment of the mitochondrial cytochrome oxidase I (COI) gene to examine the diversity of shark filets and fins collected from markets and restaurants island-wide in Taiwan.ResultsAmongst the 548 tissue samples collected and sequenced, 20 major clusters were apparent by phylogenetic analyses, each of them containing individuals belonging to the same species (most with more than 95% bootstrap values), corresponding to 20 species of sharks. Additionally, Alopias pelagicus, Carcharhinus falciformis, Isurus oxyrinchus, and Prionace glauca consisted of 80% of the samples we collected, indicating that these species might be heavily consumed in Taiwan. Approximately 5% of the tissue samples used in this study were identified as species listed in CITES Appendix II, including two species of Sphyrna, C. longimanus and Carcharodon carcharias.ConclusionDNA barcoding provides an alternative method for understanding shark species composition when species-specific data is unavailable. Considering the global population decline, stock assessments of Appendix II species and highly consumed species are needed to accomplish the ultimate goal of shark conservation.

研究背景：鲨鱼鳍捕捞（shark finning）对鲨鱼的伤害性日益受到学界重视，这也引发了全球范围内对不可持续鲨鱼捕捞产业的愈发担忧。中国台湾地区的捕捞船队鲨鱼捕获量位列全球第四，约占全球总捕获量的6%。厘清台湾地区民众消费的鲨鱼物种多样性，对于制定科学的鲨鱼保护方案至关重要。然而，鲨鱼鳍仅占其总体重的5%以下，其余躯体多以鱼柳（filets）的形式在市场流通售卖，这使得通过形态学特征鉴定鲨鱼物种变得困难甚至无法实现。
研究方法：本研究采用DNA条形码技术（DNA barcoding），以线粒体细胞色素氧化酶I（mitochondrial cytochrome oxidase I, COI）基因的391bp片段为分子标记，对中国台湾地区全岛范围内市场及餐厅采集的鲨鱼鱼柳与鱼翅样本开展物种多样性分析。
研究结果：本次研究共采集并完成测序548份组织样本，经系统发育分析可划分为20个主要聚类簇，每个聚类簇均包含同一物种的个体（多数自展支持值（bootstrap values）高于95%），对应20种鲨鱼。此外，浅海长尾鲨（Alopias pelagicus）、丝鲨（Carcharhinus falciformis）、尖吻鲭鲨（Isurus oxyrinchus）及大青鲨（Prionace glauca）的样本占总样本量的80%，表明这四类物种可能是台湾地区消费的主要鲨鱼种类。本研究中约5%的组织样本被鉴定为《濒危野生动植物种国际贸易公约（Convention on International Trade in Endangered Species of Wild Fauna and Flora, CITES）》附录II所列物种，包括双髻鲨属（Sphyrna）的2个物种、长鳍真鲨（C. longimanus）及大白鲨（Carcharodon carcharias）。
研究结论：当缺乏物种特异性检测数据时，DNA条形码技术可为解析鲨鱼物种组成提供可行的替代方案。鉴于全球鲨鱼种群数量持续下降，对CITES附录II物种及高消费量鲨鱼物种开展种群评估，是实现鲨鱼保护终极目标的必要举措。