Hooking mortality of scalloped hammerhead<i>Sphyrna lewini</i>and great hammerhead<i>Sphyrna mokarran</i>sharks caught on bottom longlines

Gulak, Simon J. B.; Santiago, A.J. de Ron; Carlson, John K.

doi:10.2989/1814232x.2015.1026842

Cited by 45 publications

(42 citation statements)

References 17 publications

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“…Over a thirty-day period, GH 3 used waters 6 m or less during 93% of the time at liberty. This finding is similar to the results presented by Hueter and Manire [17], who noted that great hammerheads along the southwest coast of Florida were only seen at depths shallower than ~ 6 m. In the US bottom longline fishery, great hammerheads are most commonly captured in waters less than 20 m [6]. Roemer et al [18] described six instances of extreme shallow water habitat use by great hammerheads, five of which involved prey capture.…”

Section: Discussionsupporting

confidence: 86%

“…Great hammerheads are listed on the International Union for the Conservation of Nature (IUCN) red list as Endangered [3] and thought to be functionally extinct throughout parts of their historical range (e.g., Gulf of California, [4]). Despite a lack of a directed fishery in the northwest Atlantic Ocean, great hammerheads are caught incidentally in longline fisheries, where they suffer high at-vessel [5,6] and post-release [7,8] mortality. Given…”

Section: Introductionmentioning

confidence: 99%

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Double tagging clarifies post-release fate of great hammerheads (Sphyrna mokarran)

Drymon

Wells

2017

Anim Biotelemetry

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Background: Biotelemetry applications have advanced our understanding of many highly migratory species, but present a challenge for species that suffer high capture and/or post-release stress. Failing to accurately characterize post-release fate can obfuscate our understanding of animal movement patterns and complicate the development of effective conservation and management plans. The great hammerhead (Sphyrna mokarran) is a long-lived, highly migratory shark listed by the International Union for the Conservation of Nature as Endangered. Accordingly, we used a combination of tags designed to report horizontal position estimates and verify post-release fate, to examine movements of great hammerheads in the northern Gulf of Mexico.Results: Between May and September 2016, three individuals (one male and two females) were equipped with both fin-mounted smart position and temperature transmitting (SPOT) tags and survivorship pop-off archival tags (sPAT) to provide information on post-release fate. Tagged sharks measured 187 (F), 203 (M), and 250 (M) cm total length. All three sharks surfaced daily, yet individuals showed variability in vertical habitat use, with maximum daily depths ranging from 5 to 98 m. A single fin-mounted SPOT tag, attached to the smallest of the three sharks, reported position estimates over an 81-day period and moved a straight-line distance of approximately 400 km; however, the other two fin-mounted SPOT tags failed to generate position estimates. All three sPAT tags indicated post-release survival. Final positions of the sPAT tags from the two largest sharks suggested restricted horizontal movements (< 35 km). Conclusions:Despite their demonstrated utility on other shark species that frequent the surface, fin-mounted SPOT tags may not be the best option for tracking great hammerheads. In addition, our findings illustrate the value of double-tagging animals under certain conditions; notably, over the short monitoring period of this study, one of the three sharks tagged may have been incorrectly presumed dead had only a fin-mounted SPOT tag been used.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Double tagging clarifies post-release fate of great hammerheads (Sphyrna mokarran)

Drymon

Wells

2017

Anim Biotelemetry

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“…For example, the predictable, seasonal, return-use of specific locations, areas or migratory routes enhances vulnerability to spatially focused fishing (Chapman et al, 2015;Queiroz et al, 2016). For great hammerheads, this is particularly concerning given their declining global populations, low and diffuse abundance, sensitivity to capture mortality and demand in the fin trade (Miller et al, 2014;Gulak et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

“…Gulak et al (2015) noted that reducing soak times to avoid capture was not economically viable, thus time-area closures were discussed as a possible option to improve management. The above analysis would enable the identification of potential time-area closures that could be most effective on reducing great hammerhead catches, while minimizing lost catches of other species and effort displacement.…”

Section: Conservation and Management Implicationsmentioning

confidence: 99%

Philopatry and Regional Connectivity of the Great Hammerhead Shark, Sphyrna mokarran in the U.S. and Bahamas

et al. 2017

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A thorough understanding of movement patterns of a species is critical for designing effective conservation and management initiatives. However, generating such information for large marine vertebrates is challenging, as they typically move over long distances, live in concealing environments, are logistically difficult to capture and, as uppertrophic predators, are naturally low in abundance. Large-bodied, broadly distributed tropical shark typically restricted to coastal and shelf habitats, the great hammerhead shark Sphyrna mokarran epitomizes such challenges. Highly valued for its fins (in target and incidental fisheries), it suffers high bycatch mortality coupled with fecundity conservative life history, and as a result, is vulnerable to over-exploitation and population depletion. Although there are very little species-specific data available, the absence of recent catch records give cause to suspect substantial declines across its range. Here, we used biotelemetry techniques (acoustic and satellite), conventional tagging, laser-photogrammetry, and photo-identification to investigate the level of site fidelity/residency for great hammerheads to coastal areas in the Bahamas and U.S., and the extent of movements and connectivity of great hammerheads between the U.S. and Bahamas. Results revealed large-scale return migrations (3030 km), seasonal residency to local areas (some for 5 months), site fidelity (annual return to Bimini and Jupiter for many individuals) and numerous international movements. These findings enhance the understanding of movement ecology in great hammerhead sharks and have potential to contribute to improved conservation and management.

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“…Changes in diving behavior of other shark species have previously been attributed to stress reactions in response to the capture and handling process [e.g., 36]. Sphyrnids in particular were shown to be inherently vulnerable to capture stress [e.g., 37,38]. However, our tagging operation (from the shark being hooked to its' release) took less than 6 min; we thus consider it unlikely that the observed increase in mesopelagic excursions 2 months into the tracking period was related to a possible capture trauma.…”

Section: Discussionmentioning

confidence: 99%

Extensive use of mesopelagic waters by a Scalloped hammerhead shark (Sphyrna lewini) in the Red Sea

et al. 2017

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Background: Despite being frequently landed in fish markets along the Saudi Arabian Red Sea coast, information regarding fundamental biology of the Scalloped hammerhead shark (Sphyrna lewini) in this region is scarce. Satellite telemetry studies can generate important data on life history, describe critical habitats, and ultimately redefine management strategies for sharks. To better understand the horizontal and vertical habitat use of S. lewini in the Red Sea and to aid with potential future development of zoning and management plans for key habitats, we deployed a pop-up satellite archival transmitting tag to track a single female specimen (240 cm total length) for a tracking period of 182 days. Results:The tag was physically recovered after a deployment period of 6 months, thus providing the complete archived dataset of more than one million depth and temperature records. Based on a reconstructed, most probable track, the shark travelled a circular distance of approximately 1000 km from the central Saudi Arabian Red Sea southeastward into Sudanese waters, returning to the tagging location toward the end of the tracking period. Mesopelagic excursions to depths between 650 and 971 m occurred on 174 of the 182 days of the tracking period. Intervals between such excursions were characterized by constant oscillatory diving in the upper 100 m of the water column. Conclusions:This study provides evidence that mesopelagic habitats might be more commonly used by S. lewini than previously suggested. We identified deep diving behavior throughout the 24-h cycle over the entire 6-month tracking period. In addition to expected nightly vertical habitat use, the shark exhibited frequent mesopelagic excursions during daytime. Deep diving throughout the diel cycle has not been reported before and, while dive functionality remains unconfirmed, our study suggests that mesopelagic excursions may represent foraging events within and below deep scattering layers. Additional research aimed at resolving potential ecological, physiological and behavioral mechanisms underpinning vertical movement patterns of S. lewini will help to determine if the single individual reported here is representative of S. lewini populations in the Red Sea.

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Hooking mortality of scalloped hammerheadSphyrna lewiniand great hammerheadSphyrna mokarransharks caught on bottom longlines

Cited by 45 publications

References 17 publications

Double tagging clarifies post-release fate of great hammerheads (Sphyrna mokarran)

Double tagging clarifies post-release fate of great hammerheads (Sphyrna mokarran)

Philopatry and Regional Connectivity of the Great Hammerhead Shark, Sphyrna mokarran in the U.S. and Bahamas

Extensive use of mesopelagic waters by a Scalloped hammerhead shark (Sphyrna lewini) in the Red Sea

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