College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China; National Engineering Research Center for Oceanic Fisheries, Shanghai Ocean University, Shanghai 201306, China; Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources, Ministry of Education, Shanghai 201306, China; Key Laboratory of Oceanic Fisheries Exploitation, Ministry of Agriculture, Shanghai 201306, China; Scientific Observing and Experimental Station of Oceanic Fishery Resources, Ministry of Agriculture, Shanghai 201306, China.
College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China.
Sci Total Environ. 2022 Dec 1;850:157927. doi: 10.1016/j.scitotenv.2022.157927. Epub 2022 Aug 10.
Commercial fisheries, especially pelagic longline fisheries targeting tuna and/or swordfish, often land silky sharks (Carcharhinus falciformis), which are currently listed as vulnerable by the International Union for Conservation of Nature (IUCN). Due to increasing fishing effort and the fact that they overlap in habitat with target species, the population trend of silky sharks is declining worldwide. Understanding their relationships with environmental variables that lead to their capture by fisheries is critical for their management and conservation. Nevertheless, little is known about their size distribution in relation to environmental variables in the Pacific Ocean. Using data from the Chinese Observer Tuna Longline fishery from 2010 to 2020, this study developed a species distribution model (SDM) to analyze the relationships between silky shark size distribution patterns and environmental variables and spatio-temporal variability at fishing locations. Observed sizes ranged from 36 to 269 cm fork length (FL). The final model suggests that sea surface temperature (SST), primary production (photosynthetically available radiation, PAR), and ocean surface winds were the key environmental variables shaping size distribution patterns of silky sharks in the Pacific. A high proportion of larger silky sharks has been predicted in areas associated with productive upwelling systems. In addition, the model predicted that larger specimens (>140 cm FL) occur near the equator, and smaller specimens farther from the equator but still in tropical regions. Two regions in the eastern Pacific (the coastal upwelling area off northern Peru and the waters around the Galapagos Islands) seem to be important locations for larger specimens. The size distribution patterns of silky sharks in relation to environmental variables presented in this study illustrate how this species segregates spatially and temporally and presents potential habitat preference areas. The information obtained in the present study is critical in the quest for management and conservation of menaced species such as the silky shark.
商业渔业，特别是以金枪鱼和/或剑鱼为目标的远洋延绳钓渔业，经常捕获到灰鲭鲨（Carcharhinus falciformis），这种鲨鱼目前被国际自然保护联盟（IUCN）列为易危物种。由于捕捞努力的增加以及它们与目标物种在栖息地重叠，灰鲭鲨的种群趋势在全球范围内正在下降。了解它们与导致被捕捞到渔业的环境变量之间的关系对于它们的管理和保护至关重要。然而，人们对太平洋中灰鲭鲨的大小分布与环境变量之间的关系知之甚少。本研究利用 2010 年至 2020 年中国金枪鱼延绳钓渔业的数据，开发了物种分布模型（SDM），以分析灰鲭鲨大小分布模式与环境变量以及捕捞地点时空变化之间的关系。观察到的大小范围从 36 到 269 厘米叉长（FL）。最终模型表明，海面温度（SST）、初级生产力（光合有效辐射，PAR）和海洋表面风是塑造太平洋灰鲭鲨大小分布模式的关键环境变量。在与生产力上升流系统相关的区域，预测会有更大比例的灰鲭鲨。此外，该模型预测较大的标本（>140 厘米 FL）出现在赤道附近，而较小的标本则离赤道更远，但仍在热带地区。东太平洋的两个区域（秘鲁北部沿海上升流区和加拉帕戈斯群岛周围水域）似乎是较大标本的重要地点。本研究中提出的灰鲭鲨大小分布模式与环境变量之间的关系说明了该物种在空间和时间上的分隔方式，并呈现了潜在的栖息地偏好区域。本研究获得的信息对于灰鲭鲨等受威胁物种的管理和保护至关重要。
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