Samoilys Melita, Osuka Kennedy E, Roche Ronan, Koldewey Heather, Chabanet Pascale
CORDIO East Africa, Mombasa, Kenya.
Department of Biology, University of Oxford, Oxford, UK.
Conserv Biol. 2025 Aug;39(4):e14430. doi: 10.1111/cobi.14430. Epub 2025 Jan 24.
Predatory and large-bodied coral reef fishes have fundamental roles in the functioning and biodiversity of coral reef ecosystems, but their populations are declining, largely due to overexploitation in fisheries. These fishes include sharks, groupers, Humphead wrasse (Cheilinus undulatus), and Green Humphead parrotfish (Bolbometopon muricatum). In the western Indian Ocean, this situation is exacerbated by limited population data on these fishes, including from conventional visual census methods, which limit the surface area surveyed. We developed a rapid timed scuba swim survey approach for application over large areas for estimation of the abundance of large-bodied reef fishes and assessment of the effectiveness of marine protected areas (MPAs) in maintaining these species' populations. Using this method, we sampled 7 regions in the western central Indian Ocean and Gulf of Aden, including 2 remote reference locations where fishing is prohibited. Eight families were selected for the surveys from across 3 categories: pelagic, demersal, and large-bodied single species. Sharks (Carcharhinidae) were absent in 5 of the 7 regions, observed only in Mozambique and the Chagos Archipelago. Tunas (Scombridae) and barracudas (Sphyraenidae) were rarely observed (none in Madagascar, Djibouti, and Iles Glorieuses). The Giant grouper (Epinephelus lanceolatus) was absent in all regions, Humphead wrasse was absent in Comoros and Iles Glorieuses, and Green Humphead parrotfish was observed at only one site in Tanzania. The MPAs were not effective in protecting these single large-bodied species or the 4 pelagic families, except for sharks in the highly protected reference locations. However, MPAs with medium levels of protection were effective in maintaining the abundance of some demersal families, notably large-bodied groupers. Our results support the hypothesis of local extirpation of these large-bodied fishes on many coral reefs in the western Indian Ocean.
肉食性和大型珊瑚礁鱼类在珊瑚礁生态系统的功能和生物多样性方面发挥着重要作用，但它们的种群数量正在下降，主要原因是渔业过度捕捞。这些鱼类包括鲨鱼、石斑鱼、波纹唇鱼（苏眉鱼）和曲纹唇鱼。在西印度洋，这些鱼类的种群数据有限，包括传统目视普查方法获取的数据，这限制了调查的表面积，使得情况更加严峻。我们开发了一种快速定时水肺游泳调查方法，用于大面积区域，以估计大型珊瑚礁鱼类的数量，并评估海洋保护区（MPA）在维持这些物种数量方面的有效性。使用这种方法，我们对印度洋中西部和亚丁湾的7个区域进行了采样，包括2个禁止捕鱼的偏远参考地点。从远洋、底栖和大型单一物种这3个类别中选择了8个科进行调查。7个区域中有5个区域没有鲨鱼（真鲨科），仅在莫桑比克和查戈斯群岛观察到鲨鱼。金枪鱼（鲭科）和梭子鱼（魣科）很少被观察到（在马达加斯加、吉布提和科摩罗群岛均未观察到）。所有区域均未发现鞍带石斑鱼，科摩罗和科摩罗群岛没有波纹唇鱼，曲纹唇鱼仅在坦桑尼亚的一个地点被观察到。除了在高度保护的参考地点的鲨鱼外，海洋保护区在保护这些单一大型物种或4个远洋科方面并不有效。然而，中等保护水平的海洋保护区在维持一些底栖科的数量方面是有效的，特别是大型石斑鱼。我们的结果支持了西印度洋许多珊瑚礁上这些大型鱼类局部灭绝的假设。
