Quantitative estimates of post-release survival rates of sharks captured in Pacific tuna longline fisheries reveal handling and discard practices that improve survivorship

Hutchinson, Melanie; Siders, Zachary A.; Stahl, Jennifer; Bigelow, Keith

doi:10.25923/0m3c-2577

Cited by 4 publications

(9 citation statements)

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“…Further, the proportion of bite-offs to the number of sharks caught (23.4%) suggests that a significant number of sharks may fail to be accounted for in longline fisheries catch statistics and population assessments when monofilament leaders are used. Therefore, while switching gear types to monofilament may provide an effective mechanism to allow sharks to free themselves from fishing gear and reduce shark mortality rates [28], this could result in an underestimation of shark interaction rates which has significant implications for stock assessment and fisheries management globally [16]. U.S. Pacific observer programs are not required to include the number of bite-offs in a set.…”

Section: Discussionmentioning

confidence: 99%

“…This includes a no retention conservation and management measure in the Western and Central Pacific Fisheries Commission [25][26][27] that also requires that sharks be released in a 'manner that minimizes harm' (CMM 2019-04). Although at present, specific guidelines and/or regulations to release sharks with minimal harm do not exist (but see [28]).…”

Section: Introductionmentioning

confidence: 99%

“…In U.S. Pacific longline fisheries, it is estimated that ~ 98% of all sharks caught as bycatch are discarded at sea [25] and of those, ~85% are released by fishers cutting the branchline leaving between 0.5-25 m of trailing gear attached to the animal [27,28]. This means that discarded sharks are released with a stainless steel circle hook, braided stainless steel wire (or monofilament) leader, a 45-gram weighted swivel, and an average ~ 9 m of monofilament.…”

Section: Introductionmentioning

confidence: 99%

“…This means that discarded sharks are released with a stainless steel circle hook, braided stainless steel wire (or monofilament) leader, a 45-gram weighted swivel, and an average ~ 9 m of monofilament. The length of trailing gear left on a shark at release has been shown to affect post-release survival (PRS) rates, where leaving < 1m attached to an animal can improve PRS of sharks by approximately 40% over 360 days [28]. Large quantities of trailing gear attached to animals are not only energetically costly as a result of drag but may also introduce infection and risk of disease [29,30], increase susceptibility to predation [31,32], and cause delayed mortality associated with the retention of fishing hooks [33,34].…”

Section: Introductionmentioning

confidence: 99%

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What’s the catch? Examining optimal longline fishing gear configurations to minimize negative impacts on non-target species

et al. 2022

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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What’s the catch? Examining optimal longline fishing gear configurations to minimize negative impacts on non-target species

et al. 2022

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“…Coelho et al (2012) also reported a relationship between mortality and size, with the smaller specimens having higher mortality rates than the larger sharks. Provided that best practices for handling and release are followed (Musyl and Gilman, 2019;Hutchinson et al, 2021), it is likely that releasing live blue sharks caught by longline fisheries is a complementary viable management tool to protect biomass in blue shark populations (as has been suggested in relation to the apparent recovery of the Southwest Pacific stock, Neubauer et al, 2021). It is likely mortality could be further reduced if spatiotemporal information on core habitats of the main life-history stages could be used to minimize catches of the most vulnerable classes.…”

Section: Perspectives For Research Management and Policymentioning

confidence: 99%

Global-Scale Environmental Niche and Habitat of Blue Shark (Prionace glauca) by Size and Sex: A Pivotal Step to Improving Stock Management

et al. 2022

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Blue shark (Prionace glauca) is amongst the most abundant shark species in international trade, however this highly migratory species has little effective management and the need for spatio-temporal strategies increases, possibly involving the most vulnerable stage or sex classes. We combined 265,595 blue shark observations (capture or satellite tag) with environmental data to present the first global-scale analysis of species’ habitat preferences for five size and sex classes (small juveniles, large juvenile males and females, adult males and females). We leveraged the understanding of blue shark biotic environmental associations to develop two indicators of foraging location: productivity fronts in mesotrophic areas and mesopelagic micronekton in oligotrophic environments. Temperature (at surface and mixed layer depth plus 100 m) and sea surface height anomaly were used to exclude unsuitable abiotic environments. To capture the horizontal and vertical extent of thermal habitat for the blue shark, we defined the temperature niche relative to both sea surface temperature (SST) and the temperature 100 m below the mixed layer depth (Tmld+100). We show that the lifetime foraging niche incorporates highly diverse biotic and abiotic conditions: the blue shark tends to shift from mesotrophic and temperate surface waters during juvenile stages to more oligotrophic and warm surface waters for adults. However, low productivity limits all classes of blue shark habitat in the tropical western North Atlantic, and both low productivity and warm temperatures limit habitat in most of the equatorial Indian Ocean (except for the adult males) and tropical eastern Pacific. Large females tend to have greater habitat overlap with small juveniles than large males, more defined by temperature than productivity preferences. In particular, large juvenile females tend to extend their range into higher latitudes than large males, likely due to greater tolerance to relatively cold waters. Large juvenile and adult females also seem to avoid areas with intermediate SST (~21.7-24.0°C), resulting in separation from large males mostly in the tropical and temperate latitudes in the cold and warm seasons, respectively. The habitat requirements of sensitive size- and sex-specific stages to blue shark population dynamics are essential in management to improve conservation of this near-threatened species.

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Estimating post-release mortality of long-line caught tropical tunas in the Pacific Ocean

et al. 2022

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Quantitative estimates of post-release survival rates of sharks captured in Pacific tuna longline fisheries reveal handling and discard practices that improve survivorship

Cited by 4 publications

References 0 publications

What’s the catch? Examining optimal longline fishing gear configurations to minimize negative impacts on non-target species

What’s the catch? Examining optimal longline fishing gear configurations to minimize negative impacts on non-target species

Global-Scale Environmental Niche and Habitat of Blue Shark (Prionace glauca) by Size and Sex: A Pivotal Step to Improving Stock Management

Estimating post-release mortality of long-line caught tropical tunas in the Pacific Ocean

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