'Disentangling' the advantages from gillnets in freshwater small-scale fisheries in the Brazilian Amazon

Gillnets, which are frequently used in small-scale fisheries (SSF), raise concerns regarding bycatch and conservation. This study evaluates the context of use and the potential advantages of gillnets alone compared to mixed (gillnet and other gear) and other gears in multi-species freshwater SSF, based in analyses of 36,869 fishing events in four rivers in the Brazilian Amazon (Tapajos, Negro, Madeira and Xingu) and considering five indicators: catch per unit of effort (CPUE), fish value (average income per kg), diversity and composition of fish caught, and variance of catches. Gillnets were used in most (similar to 61%) of fish landings in three of the studied rivers, and the frequency of use matches the observed advantages from gillnets in each river. Overall, the probability of gillnet use was statistically (P < 0.05) lower inside protected areas and higher when fishing in group, being also influenced by season. The highest advantages of using gillnets were to reduce variance (hence unpredictability) on the biomass of fish caught in the Tapajos River (L.Ratio = 9.59, P = 0.008), to increase CPUE (t((15220)) = - 2.94, P = 0.005 and t((15230)) = - 4.73, P < 0.001, compared to mixed and other gears, respectively) and to reduce variance (L.Ratio = 29.26, P < 0.001) in the Madeira River, and to catch more valuable fishes in the Xingu River (t((13160)) = - 3.68, P < 0.001 and t((13160)) = - 3.67, P < 0.001, compared to mixed and other gears), whereas in the Negro River, both gillnets and mixed gears increased CPUE (t((1073)) = - 2.89, P = 0.004). The gillnets could also allow fishers to harvest a higher diversity of fish. However, mixed gears provided similar or better outcomes when compared to gillnets alone. These results can inform policies aiming to manage use of gillnets while considering fishers' needs in the Brazilian Amazon and other multispecies SSF.

Automated summary

This study evaluated the context and potential advantages of using gillnets alone or in combination with other gears in multi-species freshwater small-scale fisheries in the Brazilian Amazon. The results showed that gillnets allowed for a higher diversity of fish species and reduced variance in fish catches, but mixed gears provided similar or better outcomes. These findings can inform policies aimed at managing the use of gillnets in the Brazilian Amazon and other similar fisheries.