Earth and Environmental Science Department, University of Milano Bicocca, Piazza Della Scienza 1, 20126, Milano, Italy; South African Shark Conservancy (SASC), Hermanus, 7200, Western Cape, South Africa.
South African Shark Conservancy (SASC), Hermanus, 7200, Western Cape, South Africa.
J Environ Manage. 2022 Oct 1;319:115691. doi: 10.1016/j.jenvman.2022.115691. Epub 2022 Jul 12.
Chondrichthyans are threatened worldwide due to their life-history traits combined with a plethora of anthropogenic impacts that are causing populations to collapse. Marine Protected Areas (MPAs) are a conservation option, but their efficacy for chondrichthyans is still unclear. Conservation efforts might be challenging especially in developing countries, due to a lack of resources and monitoring and limited data and stakeholder support. Here Baited Remote Underwater Stereo-Video systems (stereo-BRUVs) were deployed inside and outside a small partially protected MPA (Robberg MPA, Western Cape, South Africa) to assess the status of cartilaginous fishes' assemblages and to investigate the potential benefits derived from the presence of a marine reserve. Overall, 19 chondrichthyan species in 11 different families were observed. Chondrichthyans were observed in 78.5% of the sites and, of these, 89.7% of the MPA sites showed at least one chondrichthyan, while only in the 67.5% of surrounding exploited sites a cartilaginous fish was sighted. The presence of the MPA had a significant effect on the relative abundance of batoids, threatened species and local endemics, with more observations inside the MPA than outside, indicating the potential benefit of marine reserves on species that are more vulnerable to fishing pressure. Relative abundance was generally higher inside the bay than in the exposed area, and both relative abundance and species richness decreased significantly with depth. The analysis of the body length showed that the 35.5% of species had an average body length below maturity length, indicating that the area might be used as nursery ground for different species. This study provides evidence that MPAs, even though small and partially protected, can provide benefits for chondrichthyans, specifically to threatened species, endemic species and lesser-known species. Importantly, different environmental parameters must be considered to maximize the benefits an MPA can provide.
软骨鱼类在全球范围内受到威胁，这是由于它们的生活史特征以及多种人为影响导致种群数量减少。海洋保护区（MPAs）是一种保护选择，但它们对软骨鱼类的效果仍不清楚。由于资源匮乏、监测和数据有限以及利益相关者支持有限，保护工作可能具有挑战性，特别是在发展中国家。在这里，我们在一个小型部分保护区（南非西开普省罗伯格海洋保护区）内外部署了诱饵远程水下立体视频系统（立体 BRUV），以评估软骨鱼类群落的状况，并研究海洋保护区存在的潜在益处。总的来说，我们观察到了 11 个不同科的 19 种软骨鱼类。在 78.5%的地点观察到了软骨鱼类，其中 89.7%的 MPA 地点至少观察到了一种软骨鱼类，而只有在 67.5%的周边受捕捞地点观察到了软骨鱼类。保护区的存在对板鳃鱼类、受威胁物种和地方特有物种的相对丰度有显著影响，保护区内的观察结果多于保护区外，表明海洋保护区对更易受到捕捞压力影响的物种具有潜在益处。相对丰度在海湾内通常高于暴露区，相对丰度和物种丰富度随深度显著下降。体长分析表明，35.5%的物种平均体长低于成熟体长，表明该区域可能被用作不同物种的育肥场。这项研究提供了证据，表明即使是小型和部分受保护的海洋保护区也可以为软骨鱼类提供益处，特别是对受威胁物种、特有物种和鲜为人知的物种。重要的是，必须考虑不同的环境参数，以最大限度地提高海洋保护区的益处。
