Elston Chantel, Murray Taryn S, Rogers Toby, Parkinson Matthew C, Mann Bruce Q, Daly Ryan, Filmalter John D, Cowley Paul D
South African Institute for Aquatic Biodiversity, Makhanda, South Africa.
Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa.
J Fish Biol. 2025 May;106(5):1344-1359. doi: 10.1111/jfb.15728. Epub 2024 Mar 27.
Migration is a critical aspect of ocean ecosystems, and understanding this phenomenon answers ecological and management questions. Given the difficulty in tracking ocean animals across large distances, the extent to which different ray species perform long-distance movements, such as migrations, remains unknown. This study used passive acoustic telemetry to track the movements of endemic diamond Gymnura natalensis and critically endangered duckbill Aetomylaeus bovinus rays along the South African coastline using a collaborative nationwide network of coastal acoustic receivers for up to 7 years. Duckbill rays were detected significantly more frequently than diamond rays, but both species moved between the south and east coasts of South Africa (traveling up to 1167 km). Tagged individuals were detected significantly more often in their tagging locations during summer months but traveled significantly further distances during winter months. Furthermore, movement models fitted to individual duckbill rays' annual net-squared displacement identified most individual annual movements as migratory. This evidence suggests that both diamond and duckbill rays make eastward winter migrations and return to specific areas along the coastline during the summer months. The exceptions to this were diamond rays tagged on the east coast that were not found to migrate seasonally, which supports previous research that there is intraspecific variability in migrations for ray species. These findings have implications for understanding ray migration not only on a global scale but also locally for spatial management interventions and population delineation.
洄游是海洋生态系统的一个关键方面，了解这一现象有助于解答生态和管理方面的问题。鉴于追踪海洋动物远距离活动存在困难，不同鳐类物种进行长距离移动（如洄游）的程度仍然未知。本研究利用被动声学遥测技术，通过一个覆盖全国的沿海声学接收器协作网络，对南非海岸线上的本土纳塔尔吉氏鳐和极度濒危的牛鼻鲼进行了长达7年的追踪。牛鼻鲼被探测到的频率明显高于吉氏鳐，但这两个物种都在南非的南部和东部海岸之间移动（移动距离达1167公里）。在夏季，被标记的个体在其标记地点被探测到的频率明显更高，但在冬季移动的距离明显更远。此外，根据牛鼻鲼个体的年度净平方位移拟合的移动模型表明，大多数个体的年度移动属于洄游。这一证据表明，吉氏鳐和牛鼻鲼在冬季都进行向东的洄游，并在夏季返回海岸线的特定区域。例外情况是在东海岸标记的吉氏鳐未发现有季节性洄游，这支持了之前的研究，即鳐类物种在洄游方面存在种内变异性。这些发现不仅对在全球范围内理解鳐类洄游有意义，而且对当地的空间管理干预和种群划分也有意义。
