Effects of Hook and Bait on Targeted and Bycatch Fishes in an Equatorial Atlantic Pelagic Longline Fishery

Coelho, Rui; Santos, Miguel N.; Amorim, Sérgio

doi:10.5343/bms.2011.1064

Cited by 45 publications

(76 citation statements)

References 4 publications

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“…to avoid visual clutter, revealed that it fit well, with only two significant outliers: Coelho et al . () (significantly lower relative risk of capture on circle hooks than expected from the other studies) and Ariz et al . () (significantly high relative risk of capture on circle hooks than expected from the other studies) and three additional influential studies were Gilman et al .…”

Section: Resultsmentioning

confidence: 67%

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A cross‐taxa assessment of pelagic longline by‐catch mitigation measures: conflicts and mutual benefits to elasmobranchs

et al. 2016

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Elasmobranch mortality in pelagic longline fisheries poses a risk to some populations, alters the distribution of abundance between sympatric competitors, changing ecosystem structure, processes and stability. Individual and synergistic effects on elasmobranch catch and survival from pelagic longline gear factors, including methods prescribed to mitigate bycatch of other vulnerable taxa, were determined. Overall relative risk of higher circle vs. J-shaped hook shark catch rates conditioned on potentially informative moderators, from 30 studies, was estimated using an inverse-precision weighted mixed-effects meta-regression modelling approach. Sharks had a 1.20 times (95% CI: 1.03-1.39) significantly higher pooled relative risk of capture on circle hooks, with two significant moderators. The pooled relative risk estimate of ray circle hook catch from 15 studies was not significant (RR = 1.22, 95% CI: 0.89-1.66) with no significant moderators. From a literature review, wire leaders had higher shark catch and haulback mortality than monofilament. Interacting effects of hook, bait and leader affect shark catch rates: hook shape and width and bait type determine hooking position and ability to sever monofilament leaders. Circle hooks increased elasmobranch catch, but reduced haulback mortality and deep hooking relative to J-shaped hooks of the same or narrower width. Using fish vs. squid for bait increased shark catch and deep hooking. Pelagic stingray (Pteroplatytrygon violacea) catch and mortality were lower on wider hooks. Using circle instead of J-shaped hooks and fish instead of squid for bait, while benefitting sea turtles, odontocetes and possibly seabirds, exacerbates elasmobranch catch and injury, therefore warranting fishery-specific assessments to determine relative risks.

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Section: Resultsmentioning

confidence: 67%

“…() (crocodile shark, Pseudocarcharias kamoharai ) and Coelho et al . () (bigeye thresher, Alopias superciliosus ) were atypical. Pelagic shark species found in either just oceanic habitats or both oceanic and coastal habitats other than blue shark were the main caught shark species for 9 of the 30 studies.…”

Section: Discussionmentioning

confidence: 99%

A cross‐taxa assessment of pelagic longline by‐catch mitigation measures: conflicts and mutual benefits to elasmobranchs

et al. 2016

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“…Other fisheries may use other types of hooks (e.g., circle hooks, tuna hooks, or a combination of different types). For some species, including the blue shark, J-style hooks have already been shown to cause higher hooking mortality rates than circle hooks (Carruthers et al 2009); however, for the elasmobranch species that are most frequently discarded (e.g., bigeye thresher, crocodile shark, pelagic stingray and manta rays) Coelho et al (2012) showed that the hook style (J-style vs. circle hooks) was unrelated to hooking mortality. The logistic models used in our study seem to be adequate for evaluating the contribution of potential explanatory variables (e.g., sex, region and specimen size) to the mortality odds-ratio estimates, even though the explanatory abilities of the final models are relatively low.…”

Section: Discussionmentioning

confidence: 96%

An overview of the hooking mortality of elasmobranchs caught in a swordfish pelagic longline fishery in the Atlantic Ocean

Coelho

Fernandez‐Carvalho

Lino

et al. 2012

Aquat. Living Resour.

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-Hooking (or "at-haulback") fishing mortality was analysed in elasmobranchs captured by Portuguese longliners targeting swordfish in the Atlantic Ocean. Information was collected by on-board fishery observers who monitored 834 longline fishing sets between August 2008 and December 2011, and recorded information on 36 067 elasmobranch specimens from 21 different taxa. The hooking mortality proportions were species-specific, with some species having relatively high percentages of live specimens at time of haulback (e.g., blue shark, crocodile shark, pelagic stingray, manta, devil and eagle rays), while others had higher percentages of dead specimens (e.g., smooth hammerhead, silky shark, bigeye thresher). For the most captured species (Prionace glauca, Pseudocarcharias kamoharai, Isurus oxyrinchus and Alopias superciliosus), logistic generalized linear models (GLMs) were carried out to compare the mortality rates between sexes, specimen sizes and the regions of operation of the fleet. The sex-specific proportions of hooking mortality were significantly different for blue and crocodile sharks, with the males of both species having higher proportions of hooking mortality than the females. Specimen size was significant for predicting the hooking mortality for blue and shortfin mako sharks: in both cases, the larger specimens had lower odds of dying due to the fishing process. There were differences in the hooking mortality depending on the region of operation of the fleet, but those differences were also species-specific. For blue and crocodile sharks, the hooking mortality was higher in the Equatorial and southern Atlantic areas (when compared to the NE Atlantic region), while the opposite was observed for the shortfin mako, with lower mortality rates in the NE tropical area compared with the other regions. The results presented in this paper can be integrated into future ecological risk assessment analysis for pelagic elasmobranchs. Furthermore, the new information can be used to evaluate the impact of recent recommendations prohibiting the retention of some vulnerable elasmobranch species.

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“…Our results suggest that circle hooks would reduce at‐vessel mortality in three ram‐ventilating sharks—oceanic whitetip, scalloped hammerhead and shortfin mako. This result is particularly promising for their management because these species are commonly caught in pelagic longline fisheries (Coelho, Santos, & Amorim, ), and their conservation status is a matter of international concern. A decrease in at‐vessel mortality for bycatch of these shark species does not necessarily translate to a decrease in post‐release mortality of released individuals, however, some proportion of post‐release mortality is related to physiological stress and injuries experienced during capture (Skomal, ).…”

Section: Discussionmentioning

confidence: 99%

Catch rate and at‐vessel mortality of circle hooks versus J‐hooks in pelagic longline fisheries: A global meta‐analysis

Reinhardt¹,

Weaver²,

Latham³

et al. 2017

Fish and Fisheries

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We conducted a meta‐analysis of literature reporting on the use of circle hooks and J‐hooks in pelagic longline fisheries. Our study included more data than previous meta‐analyses of the effects of hook type, due to both a larger number of relevant studies available in recent years and a more general modelling approach. Data from 42 empirical studies were analysed using a random effects model to compare the effects of circle hooks and J‐hooks on catch rate (43 species) and at‐vessel mortality (31 species) of target and bycatch species. Catch rates with circle hooks were greater for 11 species, including four tuna species, six shark species and one Istiophorid billfish. Catch rates on circle hooks were lower for seven species, including two Istiophorid billfishes and two species of sea turtle. At‐vessel mortality was significantly lower with circle hooks in 12 species, including three tuna species, three Istiophorid billfishes, swordfish (Xiphias gladius) and three shark species. No species had significantly greater at‐vessel mortality when captured with a circle hook rather than a J‐hook. While our general approach increased model variability compared to more detailed studies, results were consistent with trends identified in previous studies that compared the catch rates and at‐vessel mortality (between hook types) for a number of species. Our results suggest that circle hooks can be a promising tool to reduce mortality of some bycatch species in pelagic longline fisheries, although the effects depend on the species and the metric (catch rate or at‐vessel mortality), emphasizing the need for fishery‐specific data in conservation and management decisions.

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Effects of Hook and Bait on Targeted and Bycatch Fishes in an Equatorial Atlantic Pelagic Longline Fishery

Cited by 45 publications

References 4 publications

A cross‐taxa assessment of pelagic longline by‐catch mitigation measures: conflicts and mutual benefits to elasmobranchs

A cross‐taxa assessment of pelagic longline by‐catch mitigation measures: conflicts and mutual benefits to elasmobranchs

An overview of the hooking mortality of elasmobranchs caught in a swordfish pelagic longline fishery in the Atlantic Ocean

Catch rate and at‐vessel mortality of circle hooks versus J‐hooks in pelagic longline fisheries: A global meta‐analysis

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