Andaman Nicobar Environment Team, North Wandoor, South Andaman, Andaman and Nicobar Island, India.
Wildlife Conservation Society, Kodigehalli, Bengaluru, Karnataka, India.
PLoS One. 2020 Oct 29;15(10):e0231069. doi: 10.1371/journal.pone.0231069. eCollection 2020.
Detailed information on shark and ray fisheries in the Andaman and Nicobar Islands, India are limited, including information on the diversity and biological characteristics of these species. We carried out fish landing surveys in South Andamans from January 2017 to May 2018, a comprehensive and cost-effective way to fill this data gap. We sampled 5,742 individuals representing 57 shark and ray species landed from six types of fishing gears. Of the 36 species of sharks and 21 species of rays landed, six species of sharks (Loxodon macrorhinus, Carcharhinus amblyrhynchos, Sphyrna lewini, C. albimarginatus, C. brevipinna, and Paragaleus randalli) comprised 83.35% of shark landings, while three species of rays (Pateobatis jenkinsii, Himantura leoparda and H. tutul) comprised 48.82% of ray landings, suggesting a species dominance in the catch or fishing region. We provide insights into the biology of species with extensions in maximum size for seven shark species. Additionally, we document an increase in the known ray diversity for the islands and for India with three previously unreported ray species. We found that amongst sharks, mature individuals of small-bodied species (63.48% males of total landings of species less than 1.5 m total length when mature) and immature individuals of larger species (84.79% males of total landings of species larger than 1.5 m total length when mature) were mostly landed; whereas for rays, mature individuals were predominantly landed (80.71% males of total landings) likely reflecting differences in habitat preferences along life-history stages across species and fishing gear. The largest size range in sharks was recorded in landings from pelagic longlines and gillnets. Further, the study emphasizes the overlap between critical habitats and fishing grounds, where immature sharks and gravid females were landed in large quantities which might be unsustainable in the long-term. Landings were female-biased in C. amblyrhynchos, S. lewini and P. jenkinsii, and male-biased in L. macrorhinus and H. leoparda, indicating either spatio-temporal or gear-specific sexual segregation in these species. Understanding seasonal and biological variability in the shark and ray landings over a longer study period across different fisheries will inform future conservation and fishery management measures for these species in the Andaman and Nicobar Islands.
印度安达曼和尼科巴群岛的鲨鱼和鳐鱼渔业的详细信息有限，包括这些物种的多样性和生物学特征的信息。我们于 2017 年 1 月至 2018 年 5 月在南安达曼进行了鱼类登陆调查，这是填补这一数据空白的一种全面且具有成本效益的方法。我们从六种渔具中采集了 5742 个代表从登陆的 57 种鲨鱼和鳐鱼的个体。在登陆的 36 种鲨鱼和 21 种鳐鱼中，有 6 种鲨鱼（长吻锯鲨、湾鳄、柠檬鲨、白边真鲨、短吻真鲨和小眼真鲨）占鲨鱼登陆量的 83.35%，3 种鳐鱼（菲律宾魟、豹纹魟和长尾魟）占鳐鱼登陆量的 48.82%，这表明在渔获或捕捞区域存在物种优势。我们提供了关于七种鲨鱼物种最大尺寸扩展的生物学见解。此外，我们记录了该群岛和印度的已知鳐鱼多样性增加，有三种以前未报告过的鳐鱼物种。我们发现，在鲨鱼中，成熟个体的小体型物种（63.48%的雄性是成熟个体时体长小于 1.5 米的物种）和未成熟个体的大型物种（84.79%的雄性是成熟个体时体长大于 1.5 米的物种）主要被登陆；而对于鳐鱼，成熟个体主要被登陆（80.71%的雄性是成熟个体时的总登陆量），这可能反映了不同物种和渔具在生命史阶段对栖息地偏好的差异。在延绳钓和刺网渔获的鲨鱼中记录了最大的体型范围。此外，该研究强调了关键生境和捕捞区之间的重叠，在这些区域大量捕捞未成年鲨鱼和怀孕的雌性鲨鱼，这在长期内可能是不可持续的。在 C. amblyrhynchos、S. lewini 和 P. jenkinsii 中，雌性偏多，而在 L. macrorhinus 和 H. leoparda 中，雄性偏多，这表明这些物种在空间或时间上或渔具特定的性别分离。在不同渔业中，通过更长的研究周期了解鲨鱼和鳐鱼渔获的季节性和生物变异性，将为安达曼和尼科巴群岛这些物种的未来保护和渔业管理措施提供信息。
