Department of Ecology and Evolutionary Biology, University of Science, Ho Chi Minh City, Vietnam.
Vietnam National University, Ho Chi Minh City, Vietnam.
PLoS One. 2021 Jun 10;16(6):e0252769. doi: 10.1371/journal.pone.0252769. eCollection 2021.
To improve our knowledge of the migration pathway of a highly threatened fish species along the Mekong River, strontium isotope ratios (87Sr/86Sr) and 18 trace element concentrations were measured in the water and in the otoliths of an anadromous catfish, Pangasius krempfi, to infer its natal origin and potential migration pathways. Water was sampled at 18 locations along the mainstream, tributaries and distributaries of the Mekong River. To check for accuracy and precision, measurements of the 87Sr/86Sr ratios and trace element concentrations were then compared in two laboratories that use different analytical methods. Differences in trace element concentrations between locations were not significant and could not, therefore, be used to discriminate between migration pathways. However, the Mekong mainstream, tributaries and distributaries could all be discriminated using Sr isotopes. The 87Sr/86Sr profiles recorded in P. krempfi otoliths showed that there were three contingents with obligate freshwater hatching and variable spawning sites along the Mekong mainstream, from Phnom Penh (Cambodia) to Nong Khai (Thailand) or further. After hatching, the fish migrated more or less rapidly to the Mekong Delta and then settled for most of their lifetime in brackish water. Spawning habitats and migration routes may be threatened by habitat shifts and the increasing number of hydropower dams along the river, especially the contingents born above Khone Falls (Laos). The conservation of P. krempfi, as well as other migratory fish in the Mekong River, requires agreements, common actions and management by all countries along the Mekong River. This study highlighted the importance of using both Sr/Ca and 87Sr/86Sr ratios to understand life history of anadromous fishes as the 87Sr/86Sr ratio in the water was shown to be less effective than the Sr/Ca ratio in identifying movements between different saline areas.
为了提高我们对湄公河流域高度濒危鱼类洄游路径的认识，本研究测定了洄游性湄公河鲶（Pangasius krempfi）的耳石和水体中锶同位素比值（87Sr/86Sr）和 18 种微量元素浓度，以推断其出生地和潜在洄游路径。在湄公河干流、支流和分流的 18 个地点采集了水样。为了检查准确性和精密度，然后在使用不同分析方法的两个实验室中比较了 87Sr/86Sr 比值和微量元素浓度的测量值。位置之间的微量元素浓度差异不显著，因此不能用于区分洄游路径。然而，使用锶同位素可以区分湄公河干流、支流和分流。在 P. krempfi 耳石中记录的 87Sr/86Sr 剖面表明，有三个群体具有沿湄公河干流从金边（柬埔寨）到廊开（泰国）或更远的地方进行淡水孵化和可变产卵地的强制性要求。孵化后，鱼类或多或少迅速迁移到湄公河三角洲，然后在半咸水中定居大部分生命。产卵栖息地和迁徙路线可能受到栖息地变化和河流上越来越多的水电大坝的威胁，特别是在孔瀑布（老挝）以上出生的群体。保护湄公河鲶以及湄公河中的其他洄游鱼类需要所有湄公河流域国家达成协议、采取共同行动和进行管理。本研究强调了使用 Sr/Ca 和 87Sr/86Sr 比值来了解洄游鱼类生活史的重要性，因为水 87Sr/86Sr 比值在识别不同咸水区之间的运动方面不如 Sr/Ca 比值有效。
