Variation in patterns of fish assemblage and their environmental correlates in a tropical river basin from the Gulf of Mexico slope

Abstract Understanding patterns of freshwater fish assemblage structure is key to protect them from ongoing human-induced threats to aquatic biodiversity. Yet, studies on associations between fish assemblages and habitat are lacking from many areas of high diversity in Middle America. We assessed fish assemblage structure and environmental associations from a portion of the Lacantún River sub-basin (Usumacinta River, Chiapas, Mexico). Based on environmental data and 17,462 individuals (56 species, 46 genera, and 22 families) captured from 13 sites sampled between 2017–2019, we found that stream order, distance to the Usumacinta, forest cover, temperature, and dissolved oxygen are key to explaining assemblage composition. Four clusters were found via multivariate regression tree analysis, with stream order and dissolved oxygen as defining variables. Our findings suggest that fish communities remain spatially structured even at small scales, in association to environmental gradients among habitats.

摘要 解析淡水鱼类群落的结构格局，是保护鱼类免受当前人类活动对水生生物多样性造成的持续威胁的核心前提。然而，中美洲诸多生物多样性极高的区域中，有关鱼类群落与栖息地间关联的研究仍较为匮乏。本研究以墨西哥恰帕斯州乌苏马辛塔河（Usumacinta River）流域的拉坎通河（Lacantún River）子流域部分区段为研究对象，评估了该区域的鱼类群落结构及其与环境因子的关联。基于2017至2019年间对13个采样点的调查数据，研究共捕获17462尾鱼类个体，隶属于22科、46属、56种；结合同期采集的环境数据，分析发现河流级序、距乌苏马辛塔河的距离、森林覆盖率、水温以及溶解氧是解释群落组成的关键环境因子。通过多元回归树（multivariate regression tree）分析，本研究共划分出4个鱼类群落集群，其划分依据为河流级序与溶解氧两个变量。本研究结果表明，即使在小尺度范围内，鱼类群落仍会随着不同栖息地间的环境梯度呈现出空间结构特征。