Foraging behavior of lactating South American sea lions (Otaria flavescens) and spatial–temporal resource overlap with the Uruguayan fisheries

• Published in: Deep-sea research. Part 2. Topical studies in oceanography 2013-04, Vol.88-89, p.106-119
• Main Authors: Riet-Sapriza, Federico G., Costa, Daniel P., Franco-Trecu, Valentina, Marín, Yamandú, Chocca, Julio, González, Bernardo, Beathyate, Gastón, Louise Chilvers, B., Hückstadt, Luis A.
• Format: Article
• Language: English
• Subjects: Artisanal fisheries; Bottom trawl; Earth sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Foraging behavior; Marine and continental quaternary; Marine geology; Otaria flavescens; Overlap index; Physics of the oceans; South American sea lions; Surficial geology
• ISSN: 0967-0645; 1879-0100
• DOI: 10.1016/j.dsr2.2012.09.005

Resource competition between fisheries and marine mammal continue to raise concern worldwide. Understanding this complex conflict requires data on spatial and dietary overlap of marine mammal and fisheries. In Uruguay the South American sea lions population has been dramatically declining over the past decade. The reasons for this population decline are unknown but may include the following: (1) direct harvesting; (2) reduced prey availability and distribution as a consequence of environmental change; or (3) biological interaction with fisheries. This study aims to determine resource overlap and competition between South American sea lions (SASL, Otaria flavescens, n=10) and the artisanal fisheries (AF), and the coastal bottom trawl fisheries (CBTF). We integrated data on sea lions diet (scat analysis), spatial and annual consumption estimates; and foraging behavior-satellite-tracking data from lactating SASL with data on fishing effort areas and fisheries landings. We found that lactating SASL are benthic divers and forage in shallow water within the continental shelf. SASL's foraging areas overlapped with CBTF and AF fisheries operational areas. Dietary analysis indicated a high degree of overlap between the diet of SASL and the AF and CBTF fisheries catch. The results of our work show differing degrees of spatial resource overlap with AF and CBTF, highlighting that there are differences in potential impact from each fishery; and that different management/conservation approaches may need to be taken to solve the fisheries-SASL conflict.