June 21, 2024

Seasonal Variability of South American Fur Seals (Arctocephalus australis) and Sea Lions (Otaria flavescens) in Two Haulouts and Interactions with Small-Scale Fisheries Off the Coast of Montevideo, Uruguay


Analía Bombau and Diana Szteren


Abstract: Conflicts between marine mammals and fisheries occur worldwide. Uruguay is an important breeding area of two pinniped species: the South American fur seal (Arctocephalus australis) and the South American sea lion (Otaria flavescens). Sea lions frequently interact with small-scale fisheries as their coastal feeding area coincides with the fishing zone used by coastal fisheries. In recent years, fishers have reported the presence of pinnipeds in small rookeries, Las Pipas and Isla de Flores, off the coast of Montevideo. The aim of this study was to assess the seasonal variability of both species at these two haulouts and to monitor their interactions with the small-scale fishery. We considered interactions to be when the presence of pinnipeds or predation or damages on catches were recorded during fishing operations. Between February 2013 and April 2014, six pinniped counts were made at each haulout; and between November 2013 and May 2014, 19 fishing events were monitored aboard fishing boats. Most animals in the colonies were adult males. The maximum number was recorded at Las Pipas in winter (160 animals). Sea lions were recorded throughout the year, while fur seals were only recorded in winter. In contrast, at Isla de Flores, only between 10 and 20 sea lions were recorded. Additionally, fishery catches were low (between 3 and 92 kg per fishing event). The catches per unit of effort were significantly higher in summer and autumn than in spring. However, catches did not differ significantly in the presence or absence of interactions. Sea lion predation varied from 0 to 1.72 kg per fishing event, averaging 2.37% of the potential catches. Interactions between sea lions and fishing operations were low in spring and summer, and the animals involved were mostly subadult and adult males. The fishing events with interactions and the abundance of pinnipeds were minimal in summer and maximal in autumn. In conclusion, the abundance of pinnipeds at the two haulouts can be explained by the reproductive cycles of these species, but also as a response of some animals to an increase in local food associated with the small-scale fisheries.
Key Words: abundance, haulout, interaction with fisheries, South American fur seals, Arctocephalus australis, South American sea lions, Otaria flavescens
Document Type: Research Article
DOI: https://doi.org/10.1578/AM.43.5.2017.479
Page Numbers: 479-491

Info SKU: Vol__43__Iss__5__Bombau Category: