Fishers’ knowledge on abundance and trophic interactions of the freshwater fish Plagioscion squamosissimus (Perciformes: Sciaenidae) in two Amazonian rivers

Abstract Small-scale fisheries provide income and food security to local peoples around the world. In the Brazilian Amazon, the pescada (Plagioscion squamosissimus) is among the fishes that contributes most to catches in small-scale fisheries. Our main goal was to evaluate the abundance, size, relevance to small-scale fisheries and trophic ecology of P. squamosissimus in the Tapajós and Tocantins rivers, in the Brazilian Amazon. We combined data from fishers’ local ecological knowledge (LEK) and fish sampling. We expected that fishers in the Tapajós River, less altered by anthropic changes, would cite a higher abundance, larger size and more prey and predators of P. squamosissimus. We interviewed 61 and 33 fishers and sampled fish in nine and five sites in the Tapajós and Tocantins rivers, respectively. The comparison between fishers’ citations and fish sampled indicated a higher relevance of P. squamosissimus to fishers in the Tapajós River, where this fish had an average larger size and where the fishers mentioned more food items. This pattern could be partially related to the history of anthropogenic changes in the Tocantins River. These results indicated that P. squamosissimus is a generalist fish, which could be resilient to fishing and environmental pressures.

摘要 小型渔业为全球各地的本地民众提供收入与粮食保障。在巴西亚马逊流域，锯脂鲤鲈（pescada, *Plagioscion squamosissimus*）是小型渔业捕捞量最高的鱼种之一。本研究的核心目标为评估巴西亚马逊流域塔帕若斯河（Tapajós）与托坎廷斯河（Tocantins）中锯脂鲤鲈的种群丰度、个体规格、在小型渔业中的重要性及其营养生态特征。我们整合了渔民本地生态知识（local ecological knowledge, LEK）与鱼类采样获取的数据，并提出如下假设：受人类活动干扰更少的塔帕若斯河沿岸渔民，会报告该鱼种更高的种群丰度、更大的个体规格，以及更多的猎物与天敌种类。我们分别对塔帕若斯河的61名渔民、托坎廷斯河的33名渔民开展了访谈，并在塔帕若斯河的9个采样点、托坎廷斯河的5个采样点进行了鱼类采样。对渔民访谈结果与鱼类采样数据的对比分析显示，塔帕若斯河沿岸渔民对锯脂鲤鲈的依赖程度更高；该河段的锯脂鲤鲈平均个体规格更大，且渔民提及的该鱼种食物类群也更为丰富。这一格局可能与托坎廷斯河既往的人类活动干扰历史存在部分关联。本研究结果表明，锯脂鲤鲈属于广食性鱼类，对捕捞活动与环境压力具备一定的恢复能力。