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Marine Ecology Progress Series

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MEPS 639:215-232 (2020)  -  DOI:

Trophic overlap between marine mammals and fisheries in subtropical waters in the western South Atlantic

Rodrigo Machado1,2,3,*, Larissa Rosa de Oliveira1,4, Paulo Henrique Ott1,5, Manuel Haimovici6, Luis Gustavo Cardoso6, Lucas Milmann1,7, Maria Alejandra Romero8,9, Roberta Aguiar dos Santos10, Márcio Borges-Martins1,2

1Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul, Torres, RS, 95560-000, Brazil
2Universidade Federal do Rio Grande do Sul, Programa de Pós-Graduação em Biologia Animal (PPGBAN), Porto Alegre, RS, 91501-970, Brazil
3Universidade do Extremo Sul Catarinense (UNESC), Programa de Pós-Graduação em Desenvolvimento Socioeconômico (PPGDS), Criciúma, SC, 88.806-000, Brazil
4Laboratório de Ecologia de Mamíferos, Universidade do Vale do Rio dos Sinos, São Leopoldo, RS, 93022-000, Brazil
5Laboratório Biodiversidade e Conservação, Universidade Estadual do Rio Grande do Sul, Unidade do Litoral Norte, Osório, RS, 95520-000, Brazil
6Universidade Federal do Rio Grande, Instituto de Oceanografia, Laboratório de Recursos Pesqueiros Demersais e Cefalópodes, Rio Grande, RS, 96201-900, Brazil
7Universidade Estadual de Santa Cruz, Programa de Pós-Graduação em Ecologia e Conservação da Biodiversidade, Ilhéus, BA, 45662-900, Brazil
8Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos ‘Almirante Storni’, Güemes 1030 (8520) San Antonio Oeste (RN), Argentina
9Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, C1425FQB, Argentina
10Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio), Centro Nacional de Pesquisa e Conservação da Biodiversidade Marinha do Sudeste e Sul (CEPSUL), Itajaí, SC, 88301-445, Brazil
*Corresponding author:

ABSTRACT: Marine mammals and humans are apex predators and both may compete for fish in ecosystems under continuous fishing pressure. We assessed the degree of trophic overlap between prey species found in the diet of 5 marine mammals (39 specimens of sea lion Otaria flavescens, 61 fur seals Arctocephalus australis, 76 franciscana dolphins Pontoporia blainvillei, 25 bottlenose dolphins Tursiops truncatus and 28 Lahille’s bottlenose dolphins T. gephyreus) and the catches of the 6 main commercial fishing gears used in southern Brazil (coastal gillnets, oceanic gillnets, purse seine, demersal pair trawling, bottom [single] trawl and double-rig trawling) between 1993 and 2016. An adjusted general overlap index indicated an overall moderate to high overlap. Specific overlap analysis showed that O. flavescens and T. truncatus presented high trophic relationships with fisheries, followed by T. gephyreus. Smaller interactions were observed for A. australis and P. blainvillei, even though they also exploit commercial fishing resources. Coastal gillnet and pair bottom trawling are the fisheries that most target the fish species favoured by O. flavescens, T. gephyreus and T. truncatus. The information presented in this study on trophic interactions may assist decision making for both fishery management and conservation measures for these apex predators. Commercial fishing activities are a major threat to marine mammals both regionally and globally. Current levels of fishing or its intensification may lead to dramatic changes in the coastal marine food web, including additional threats to coastal marine mammal populations in southern Brazil.

KEY WORDS: Trophic interactions · Feeding ecology · Marine mammals · Fisheries · Marine conservation

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Cite this article as: Machado R, de Oliveira LR, Ott PH, Haimovici M and others (2020) Trophic overlap between marine mammals and fisheries in subtropical waters in the western South Atlantic. Mar Ecol Prog Ser 639:215-232.

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