Ingestion of fishing items by South American sea lion in southern Brazil: Indicating a neglected problem

The conflicting interactions between pinnipeds (seals, fur seals and sea lions) and fishing activities generate economic losses to the fishing industry by depredation of catch and damage to fishing gear. The latter in turn is an underreported problem for many species of pinnipeds that interact with fisheries. In this context, the present study aims to evidence gear damage caused by the South American sea lion (Otaria flavescens) during the depredation of catch, analyzing fishing items found in the stomachs of sea lions in southern Brazil. For this purpose, 46 stomachs of male South American sea lions found stranded on the southern coast of Brazil between 1993 and 2013 were analyzed. The fishing items found in the South American sea lion stomachs were identified and categorized. In 17.4% of the stomachs analyzed, fishing items were recorded. Gillnet fishing was the most representative item, being recorded in 15.2% of stomachs, followed by fishing lines (2.3%) and fishing hook with line (2.3%). The recorded items represented 79 fragments (gillnets = 88.6%, fishing line = 10% and fishing hook with line = 1.3%). The results also demonstrate an increase in the ingestion of fishing items by South American sea lions over time. The results presented here show that this type of interaction between the South American sea lion and the fishing industry, which has never been investigated in South America before, deserves more attention from researchers and fisheries managers. In this context, for a real understanding of the magnitude of the impact that South American sea lions can cause on fisheries, studies are urgently needed to estimate the impacts of these interactions, estimate the monetary costs of repairing fishing gear, and seek alternatives to minimize these problems. Still being important to mention that ingesting fishing items can cause injuring the digestive tract of sea lions, potentially causing the death of individuals or affecting animals by slower sublethal physical and chemical effects.

Automated summary

The conflicting interactions between South American sea lions and fishing activities cause economic losses and damage to fishing gear. This study analyzes the fishing items found in the stomachs of stranded sea lions in southern Brazil to demonstrate the gear damage during the depredation of catch. The results suggest that this type of interaction deserves more attention and further research.