Ichthyofauna bycatch associated with Amazonian shrimp fishing Macrobrachium amazonicum (Heller, 1862) (Decapoda, Palaeomonidae): subsidies for environmental management and fishery planning

Abstract

The traditional communities of the Lower Amazon in Pará have several fishing activities that generate jobs and income for fishers. These activities include fishing for the Amazonian shrimp Macrobrachium amazonicum practiced on the riverside of the Amazon River, around the city of Santarém (PA). The main objective of this work is to register information the ichthyofauna accompanying the Amazonian shrimp fishery, as well as its relationship with the total biomass, richness, catch per unit  effort (CPUE) and the ratio of fish to shrimp. Data were collected through the monthly monitoring in three semi-fixed traps in the fishing area from February/2018 to January/2019. The data were annotated and organized in a database to facilitate analysis. A total of 2,136 fish belonging to 24 families and 69 species were caught. The species Colomesus asellus was the most abundant, and Hypoptopoma elongatum occurring in all sampling months. The total length was low and varied between 32 mm to 275 mm, indicating the participation of many small-size species and juvenile individuals, of minor or no commercial interest. The proportion of fish-shrimp was of 0.02:35.24 kg, which demonstrates that 97% of the shrimp’s fishery production consists of the target species. However, young fish are usually discarded dead, negatively impacting their life cycle. The indexes of diversity and equitability varied along the months. This variation indicates a seasonal distribution pattern regarding the region’s hydrological regime.