Ecological Impacts of Artisanal Shrimp Trawling on Macroinvertebrate Bycatch in the Southwestern Atlantic, Brazil.

Abstract

Artisanal shrimp trawling represents an activity of considerable socioeconomic relevance, particularly in coastal communities. However, it is a non-selective fishing method known for capturing large amounts of bycatch, which negatively impacts benthic ecosystems, especially marine invertebrates. This study aimed to analyze the influence of depth, temperature, and fishing season on the distribution patterns, abundance, and biomass of macroinvertebrates captured as bycatch. Samples were collected during open and closed fishing seasons at depths ranging from 13 to 35 meters in commercial shrimp trawling operations in the Santana Archipelago, Macaé, Rio de Janeiro, Brazil. Generalized Linear Models (GLMs) were used to evaluate the effects of these environmental factors on macroinvertebrate biomass and density. The total biomass recorded was 236 kg, comprising 144 kg (61%) of macroinvertebrates and 92 kg (39%) of commercial shrimp. The shrimp-to-bycatch ratio was 1:1.6, with Crustacea accounting for the largest share of the total biomass. A total of 7,134 macroinvertebrate individuals were recorded, distributed among Crustacea (2,965 individuals; 41.56%), Mollusca (2,361; 33.10%), Cnidaria (1,709; 23.96%), Echinodermata (98; 1.37%), and Annelida (1; 0.01%). Capture rates of shrimp and macroinvertebrates varied between open and closed seasons. The high volume of bycatch highlights the need for improved management strategies in artisanal shrimp fisheries to mitigate environmental impacts in Macaé's marine ecosystems.