Influence of electric fishing lights on sink rates of baited hooks in Brazilian pelagic longline fisheries: implications for seabird bycatch

Gianuca, Dimas; Sant’Ana, Rodrigo; Neves, Tatiana

doi:10.1590/s1679-87592016092306401

Cited by 3 publications

(4 citation statements)

References 12 publications

(14 reference statements)

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“…One bird was caught during a full moon, four were caught during a waning gibbous moon, two birds were caught during the last quarter, and four birds were caught during a waning crescent moon. This high bycatch rate reinforces the need for the simultaneous utilization of three seabird bycatch mitigation measures in pelagic longline fisheries, especially in areas like the south‐west Atlantic with a high density of albatrosses and medium‐size diving petrels (Gianuca et al, ; Jiménez, Domingo, Abreu, & Brazeiro, ).…”

Section: Discussionmentioning

confidence: 70%

“…The two Lumo Lead treatments reached the relatively safe 10 m depth benchmark (Melvin, Guy, & Read, ; Petersen, Honig, et al, ) within 30 s of deployment, whereas the lead swivel placed at 3.5 m did not. The time benchmark of 30 s corresponds to the period hooks would be protected by a toriline with a 100 m aerial extent, assuming a setting speed of 6 kn and the use of 60 g weights at 3.5 m from the hook, which is typical of the Brazilian fleet (Gianuca et al, ). However, in the absence of a toriline, birds can access baited hooks immediately astern of the vessel irrespective of the line weighting regime.…”

Section: Discussionmentioning

confidence: 99%

“…The mean depths of baited hooks 30 s after deployment were compared using a one‐way ANOVA. This time was chosen as a benchmark as it represents the approximate time baited hooks would be protected by a 100 m toriline, assuming a vessel speed of 6 kn (the average speed in the Brazilian fleet) and the use of a 60 g lead swivel placed at 3.5 m from the hook (Gianuca, Sant'Ana, & Neves, ). For all tests, a significance level of 95% ( α = 0.05) was used.…”

Section: Methodsmentioning

confidence: 99%

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Improved line weighting reduces seabird bycatch without affecting fish catch in the Brazilian pelagic longline fishery

Santos

Silva-Costa

Sant’Ana

et al. 2019

Aquatic Conservation

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1. Increasing the sink rate of baited hooks by adding weights in close proximity to the hook is crucial to reduce seabird mortality in pelagic longline fisheries. However, weights placed next to the hook are a cause for concern for fishing crew because they can fly back in the event of a line break, injuring deck crew.2. Lumo Leads, an alternative weight system designed to slide in the event of a line break, and therefore prevent accidents, were trialled in pelagic longline fisheries off southern Brazil. Four fishing trips were conducted and 26,377 hooks sampled to compare sink rates, seabird bycatch rates and catch rates of target species between three treatments: (1) 60 g Lumo Lead attached at 1.0 m from the hook;(2) 60 g Lumo Lead at 3.5 m; and (3) 60 g leaded swivels at 3.5 m from the hook. A LumoLead placed at 1.0 m from the hook resulted in a faster sink rate and caught fewer seabirds (0.11 birds per unit of effort [BPUE]) when compared with a Lumo Lead (0.33 BPUE) or weighted swivel (0.85 BPUE) placed at 3.5 m. The bycatch with Lumo Lead placed at 1.0 m from the hook was 90% lower than the bycatch of Lumo Lead or weighted swivel placed at 3.5 m combined. There was no difference in the catch rates of target species between the three treatments.4. These findings support a growing body of evidence that placing weights close to the hook reduces seabird bycatch without affecting the catchability of the target species. The high seabird bycatch rates recorded despite night setting and recommended line weighting regimes reinforces the need of simultaneous deployment of a toriline with these other two mitigation measures to reduce seabird bycatch to negligible levels in the south-west Atlantic.

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Improved line weighting reduces seabird bycatch without affecting fish catch in the Brazilian pelagic longline fishery

Santos

Silva-Costa

Sant’Ana

et al. 2019

Aquatic Conservation

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“…Lightstick wavelength and flicker rate can affect species‐ and ontogenetic stage‐specific catch rates of fishes and marine turtles (Afonso et al, 2021; Crognale et al, 2008; Wang et al, 2007). Battery‐powered fishing lights can increase the sink rate of baited hooks, reducing seabird catch risk (Gianuca et al, 2016)—primarily problematic at higher latitudes, seabird bycatch is not documented to occur in the Palau fishery.…”

Section: Discussionmentioning

confidence: 99%

Evidence from interpretable machine learning to inform spatial management of Palau's tuna fisheries

Gilman,

Chaloupka

2024

Ecosphere

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Static and dynamic area‐based management tools hold substantial potential to balance socioeconomic benefits derived from fisheries and costs from bycatch mortality of at‐risk species. Palau longline fisheries have high bycatch of at‐risk species including the olive ridley marine turtle and silky and blue sharks. This study analyzed a two decades‐long time series of observer and electronic monitoring datasets from the Palau distant‐water and locally‐based pelagic longline fisheries. An interpretable or explainable machine learning‐based modeling approach was used to derive spatially resolved species‐specific catch rate predictions. These models were conditioned on a suite of potentially informative environmental, bathymetric, ocean‐climate metric, vessel, monitoring system, and set‐specific operational predictors. Overall, there would be limited ecological tradeoffs from focusing fishing effort within primary catch rate hotspots for target bigeye and yellowfin tunas. Mean field prediction surfaces also defined catch rate hotspots for at‐risk species of silky and blue sharks, olive ridley turtle, and pelagic stingray, which did not overlap the hotspots for target species. The predicted target species hotspots, however, overlap olive ridley and pelagic stingray warmspots. Results also identify opportunities for temporally dynamic spatial management to control catch rates of target and bycatch species. Management of fishery operational predictors of fishing depth and soak duration present additional opportunities to balance catch rates of at‐risk bycatch and target species. A transition to employing fleetwide or vessel‐based output controls that effectively constrain the fishery would alter the spatial management strategy to focus on zones with the lowest ratio of at‐risk bycatch to commercial catch. Our findings support evidence‐informed evaluation of spatial management strategies and complementary measures to meet objectives for balancing socioeconomic benefits derived from target species catch with costs to threatened species.

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Guidelines for Evaluating Artificial Light to Mitigate Unwanted Fisheries Bycatch

Yochum,

Karlsen,

Senko

et al. 2024

Reviews in Fisheries Science & Aquaculture

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Influence of electric fishing lights on sink rates of baited hooks in Brazilian pelagic longline fisheries: implications for seabird bycatch

Cited by 3 publications

References 12 publications

Improved line weighting reduces seabird bycatch without affecting fish catch in the Brazilian pelagic longline fishery

Improved line weighting reduces seabird bycatch without affecting fish catch in the Brazilian pelagic longline fishery

Evidence from interpretable machine learning to inform spatial management of Palau's tuna fisheries

Guidelines for Evaluating Artificial Light to Mitigate Unwanted Fisheries Bycatch

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