Fisher's local ecological knowledge improves understanding of temporal changes on fishing resources in tropical rivers

Small-scale fisheries are important in developing countries, but fishing pressure and other impacts have changed the composition and decreased the abundance of fishing resources. We analyze fishers’ knowledge on temporal... [ view full abstract ]

Small-scale fisheries are important in developing countries, but fishing pressure and other impacts have changed the composition and decreased the abundance of fishing resources. We analyze fishers’ knowledge on temporal trends of composition and abundance of fish catches, comparing trends perceived by fishers located inside and outside protected areas in the Tapajos and Negro rivers, in the Brazilian Amazon. We interviewed 161 fishers in the Tapajos in four communities inside the Extractive Reserve (RESEX) of Tapajos-Arapiuns (n= 88 fishers) established in 1998 and four outside (n= 73), plus 120 fishers in Negro in four communities inside the RESEX of Unini River (n= 74) established in 2006 and four outside (n= 46). The interviews included questions about the most caught fish now (2016) and 20 years ago (hereafter, in the past), besides perceived trends in the abundance of fish caught. We considered answers regarding increase and same abundance as positive, decrease as negative and neutral when half of interviewees cited each trend. We compared the composition of fish names, which correspond to fish species (or groups of species) through the percentage similarity index. Fishers in the Tapajos cited a total of 43 fish species (names), 36 in the RESEX and 31 outside in the past; 29 in the RESEX and 28 outside now. Fishers in the Negro cited a total of 32 fish species, 28 in the RESEX and 13 outside in the past; 15 in the RESEX and 16 outside now. The composition of the catch based on fishers’ citations was similar between now and the past inside and outside the RESEX in Tapajos and Negro (all comparisons > 50 % similarity). Considering the abundance trends of fish species according to fishers, in Tapajos inside the RESEX (n= 16 species), 7 were negative, 5 neutral and 4 positive, while outside (n= 14), 8 were negative, 2 neutral and 4 positive. In the Negro River inside the RESEX all 9 species were positive, while outside (n= 9), 1 were negative, 2 neutral and 6 positive. Fishers’ knowledge indicated that composition of fish catches had not changed much along the last 20 years in the Tapajos and Negro rivers, either inside or outside the RESEXs. The scenario of trends on abundance of fish species caught now (2016) according to fishers was better in Negro (especially inside the RESEX) than in the Tapajos, where fishers indicated declines in the populations of commercial fish.