Fishers' knowledge indicates temporal changes in composition and abundance of fishing resources in Amazon protected areas

The local ecological knowledge (LEK) of fishermen has been applied to reconstruct temporal patterns of resource abundance and to assess resource exploitation, especially in tropical ecosystems. Protected areas (PAs) are the main conservation measure in the Amazon, but their efficacy to improve fisheries is poorly known. The main goal of this study was to apply fishermen' LEK to evaluate temporal changes in composition and abundance of exploited fish species among three different categories of PAs in the Tapajos River, Brazilian Amazon. We interviewed 203 fishers about their highest fish catches, and the main fish caught at two time periods: the beginning of their fishing careers and currently. Fishers' LEK indicated decreases in citations of larger-bodied fishes and in reported catches over time, evidencing a gradient of conservation according to PA's time of establishment and management rules. We noticed higher changes (reduced catches and smaller fish exploited) in the Environmental PA, established 10 years ago and lacking management plan and buffer zone. In National Forest, which was created 40 years ago with more restrictive management rules, fish composition and catches included larger commercial fish. The Extractive Reserve, which was created 15 years ago and lacks specific fishing rules, may be in an intermediate stage, as large fish and highest catches decreased over time, but medium and large fish are still exploited. Fishers' LEK can be an invaluable but neglected source of data on temporal patterns of fishing pressure and conservation needs, especially in tropical megadiverse, poorly known and threatened rivers.