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，犬齿仿石鲈（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与托坎廷斯河中该鱼种的种群丰度、个体规格、在小型渔业中的重要性及其营养生态特征。本研究整合了渔民本地生态知识（local ecological knowledge，LEK）与鱼类采样数据。我们预设：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，以及更多的捕食对象与天敌种类。本研究分别对塔帕若斯河与托坎廷斯河沿岸的61名和33名渔民进行了访谈，并在两条河流的9个与5个采样点开展了鱼类采样工作。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该鱼种的依赖程度更高；该河段内的该鱼种平均个体规格更大，且渔民提及的食物类群也更为丰富。该分布格局或与托坎廷斯河的人类活动干扰历史存在部分关联。本研究结果表明，该鱼种为广食性鱼类，对捕捞活动与环境压力具备一定的抗干扰能力。