Operational interactions between South American sea lions and gillnet fishing in southern Brazil

Machado, Rodrigo; Ott, Paulo Henrique; Moreno, Ignacio B.; Danilewicz, Daniel; Tavares, Maurício; Crespo, Enrique A.; Siciliano, Salvatore; Oliveira, Larissa Rosa de

doi:10.1002/aqc.2554

Cited by 29 publications

(26 citation statements)

References 23 publications

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“…Data on captures and landings were obtained from gillnet fishing monitored during on board surveys on local fishing vessels at Passo de Torres (29 ∘ 19 ′ S; 49 ∘ 43 ′ W) and Imbé (29 ∘ 58 ′ S; 50 ∘ 07 ′ W) harbours, southern Brazil (Machado et al, 2016). Twelve specimens of R. laevis from Passo de Torres were collected, and the stomachs and gonads removed.…”

mentioning

confidence: 99%

Analysis of an astounding aggregation of Ranzania laevis (Molidae: Actinopterygii) in the tropical south‐western Atlantic

Horn

Machado

Weiss

et al. 2016

Journal of Fish Biology

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Unusual catches of more than 4200 kg of the slender sunfish Ranzania laevis are described from the south-western Atlantic, corresponding to the largest aggregation records for the species. These unexpected records were associated with unusually warm currents in the area. Males and females were physiologically able to spawn at the moment of capture, suggesting the occurrence of reproductive aggregation in this species.

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mentioning

confidence: 99%

Analysis of an astounding aggregation of Ranzania laevis (Molidae: Actinopterygii) in the tropical south‐western Atlantic

Horn

Machado

Weiss

et al. 2016

Journal of Fish Biology

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“…Although the reasons for this population decline are still unknown, the interactions with fishing activities have been identified as a major cause of threat to the conservation of South American sea lions (IUCN, 2013;Crespo et al, 2012). Records of catches of South American sea lions by fishing activities are reported for gillnet fisheries in Peru (Majluf et al, 2002), Chile (Sepúlveda et al, 2007) and Uruguay (Franco-Trecu et al, 2009), for purse seine fisheries in Chile (Hückstädt and An-tezana, 2003) and Argentina (Seco Pon et al, 2013); and for trawling fisheries in Argentina (Crespo et al, 1997;Dans et al, 2003) and Chile (Reyes et al, 2013). Thus, this paper presents the first record of incidental catch of the South American sea lions in Brazilian waters and by a pair trawl fishery.…”

Section: Short Communicationmentioning

confidence: 80%

“…However, there is no information about the proportion of mortality caused by fishery interactions. Machado et al (2015) monitored 484 gillnet fishing operations in this area, between 1991 and 2012, and did not record any single incidental capture of sea lions, although fishermen stated that incidental catches may eventually occur. On the other hand, in this region it is common to find animals stranded with evidence of aggressions that may have caused the death.…”

Section: Short Communicationmentioning

confidence: 99%

Captura incidental de um leão-marinho-sul-americano na pesca de arrasto de parelha no sul do Brasil

Machado

Oliveira

Montealegre‐Quijano

2014

Neotropical Biology and Conservation

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The population of the South American sea lion, Otaria flavescens (Shaw, 1800), in Uruguay is declining at an annual rate of 1.6 to 2.0%. Although the reasons are still unknown, interactions with fishing activities have been identified as a major cause. The individuals that arrive along the coast of Brazil come from the breeding colonies off Uruguay after their breeding period. We report here the first record of incidental catch of South American sea lions in Brazilian waters by a pair trawl. On July 17 th , 2008 a young male of South American sea lion was incidentally caught during a commercial pair trawl fishing trip along the southern Brazilian coast (32º57'S, 52º31'W), in a depth ranging from 15 to 20 m. Despite being punctual, this record is an evidence of a potential major threat to South American sea lions in southern Brazil and Uruguay, since trawl industrial fishing is a very important economic activity in South Brazil.

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“…Intensive use of gillnets, especially those with smaller mesh sizes, can threaten biodiversity through by‐catch of juvenile commercial fish or endangered species of megafauna, such as cetaceans, caimans, turtles or seals (Stewart et al , ; Shester and Micheli, ). Increasing fishing effort with fixed gillnets can also increase the conflicts and negative interactions between fishers and aquatic predators, such as sea lions or dolphins (Gonzalvo et al ., ; Machado et al ., ). Gear restrictions, including those on the mesh sizes of fishing nets, can reduce fishing impacts in an ecosystem‐based management framework, especially when spatial closures are socially unacceptable (McClanahan and Cinner, ; Cinner et al ., ; Hicks and McClanahan, ).…”

Section: Introductionmentioning

confidence: 97%

Assessment of efficiency and impacts of gillnets on fish conservation in a tropical freshwater fishery

Silvano

Hallwass

Juras

et al. 2016

Aquatic Conservation

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1. Gillnets are commonly used in tropical multi-species fisheries and there is a need to investigate the comparative efficiency and impacts of this gear on fish populations and diversity. The efficiency and the impact of gillnets of distinct mesh sizes were compared in the Lower Tocantins River (Brazilian Amazon).2. Fish sampling was conducted in 12 floodplain lakes using gillnets of distinct mesh sizes and 345 fish landings were recorded. Indicators of gillnet efficiency were: (1) catch per unit of effort (CPUE) of total fish sampled; (2) CPUE of fish caught by fishers; (3) CPUE of commercial fish sampled; and (4) proportion of biomass of commercial fish sampled. Indicators of impact were: (1) the number of non-commercial fish (by-catch); (2) the proportion of fish above the length at first maturity; (3) mean fish size (length); (4) total number of fish species and of rare fish species caught.3. Gillnets of 8 cm mesh size showed a higher CPUE in fish samples and fish landings. This mesh size also showed reduced impacts (lower numbers of non-commercial fish caught and higher proportion of adult fish).4. Gillnets of 6 cm mesh size caught a smaller proportion of adult fish, smaller fish, more species and more rare species. Therefore, intensive use of these gillnets could increase the risk of regional species extinctions and impair the provision of ecosystem services by target fish.5. Gillnets of 8 cm mesh size could improve fish catches while minimizing adverse effects of gillnet fishing. The practical management recommendation would be to replace the more damaging small mesh gillnets by gillnets with intermediate mesh size. This recommendation could simultaneously protect small-sized rare species and larger fish, being broadly applicable to other small-scale and multi-species fisheries that use gillnets intensively in tropical countries with high fish diversity.

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Operational interactions between South American sea lions and gillnet fishing in southern Brazil

Cited by 29 publications

References 23 publications

Analysis of an astounding aggregation of Ranzania laevis (Molidae: Actinopterygii) in the tropical south‐western Atlantic

Analysis of an astounding aggregation of Ranzania laevis (Molidae: Actinopterygii) in the tropical south‐western Atlantic

Captura incidental de um leão-marinho-sul-americano na pesca de arrasto de parelha no sul do Brasil

Assessment of efficiency and impacts of gillnets on fish conservation in a tropical freshwater fishery

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