Distribution and movement of scalloped hammerhead<i>Sphryna lewini</i>and smooth hammerhead<i>Sphyrna zygaena</i>sharks along the east coast of southern Africa

Diemer, KM; Mann, BQ; Hussey, NE

doi:10.2989/1814232x.2011.600291

Cited by 38 publications

(30 citation statements)

References 23 publications

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“…With known spatial latitudinal and inshore v. offshore gradients in δ 13 C values (Hill et al , 2006, 2008), the authors identified a degree of sexual separation in sub‐adult S. lewini and a movement to shelf‐edge foraging in large C. obscurus . These isotopic reconstructed movements were supported by previous tag‐recapture and observation data for these species (Klimley, 1987; Hussey et al , 2009; Diemer et al , 2011). Juvenile C. obscurus also showed variable δ 13 C values compared to small S. lewini , reflecting a known migration along the South African coastline (Hussey et al , 2009).…”

Section: Ecological Applicationssupporting

confidence: 82%

Stable isotopes and elasmobranchs: tissue types, methods, applications and assumptions

Hussey

MacNeil

Olin

et al. 2012

Journal of Fish Biology

215

212

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Stable-isotope analysis (SIA) can act as a powerful ecological tracer with which to examine diet, trophic position and movement, as well as more complex questions pertaining to community dynamics and feeding strategies or behaviour among aquatic organisms. With major advances in the understanding of the methodological approaches and assumptions of SIA through dedicated experimental work in the broader literature coupled with the inherent difficulty of studying typically large, highly mobile marine predators, SIA is increasingly being used to investigate the ecology of elasmobranchs (sharks, skates and rays). Here, the current state of SIA in elasmobranchs is reviewed, focusing on available tissues for analysis, methodological issues relating to the effects of lipid extraction and urea, the experimental dynamics of isotopic incorporation, diet-tissue discrimination factors, estimating trophic position, diet and mixing models and individual specialization and niche-width analyses. These areas are discussed in terms of assumptions made when applying SIA to the study of elasmobranch ecology and the requirement that investigators standardize analytical approaches. Recommendations are made for future SIA experimental work that would improve understanding of stable-isotope dynamics and advance their application in the study of sharks, skates and rays.

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Section: Ecological Applicationssupporting

confidence: 82%

Stable isotopes and elasmobranchs: tissue types, methods, applications and assumptions

Hussey

MacNeil

Olin

et al. 2012

Journal of Fish Biology

215

212

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“…This information is summarised below.

Size and sex structure data indicate that few adult females (and especially pregnant females) occur in northern Australia, but are regularly caught in Indonesia and PNG. Considering that hammerheads sharks in other regions move to shallow nursery areas to give birth314445, this population structure suggests that a proportion adult females may migrate from Australia to Indonesia and PNG, but return to give birth to their young in nursery areas in coastal areas of northern Australia4647.

There is genetic evidence of mixing between Australian and Indonesian animals48. Current genetic analysis only provides evidence of a connection on evolutionary time scales (although it does not discount connections at shorter time scales).…”

Section: Resultsmentioning

confidence: 99%

“…Considering that hammerheads sharks in other regions move to shallow nursery areas to give birth314445, this population structure suggests that a proportion adult females may migrate from Australia to Indonesia and PNG, but return to give birth to their young in nursery areas in coastal areas of northern Australia4647.…”

Section: Resultsmentioning

confidence: 99%

Crossing lines: a multidisciplinary framework for assessing connectivity of hammerhead sharks across jurisdictional boundaries

Chin

Simpfendorfer

White

et al. 2017

Sci Rep

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Conservation and management of migratory species can be complex and challenging. International agreements such as the Convention on Migratory Species (CMS) provide policy frameworks, but assessments and management can be hampered by lack of data and tractable mechanisms to integrate disparate datasets. An assessment of scalloped (Sphyrna lewini) and great (Sphyrna mokarran) hammerhead population structure and connectivity across northern Australia, Indonesia and Papua New Guinea (PNG) was conducted to inform management responses to CMS and Convention on International Trade in Endangered Species listings of these species. An Integrated Assessment Framework (IAF) was devised to systematically incorporate data across jurisdictions and create a regional synopsis, and amalgamated a suite of data from the Australasian region. Scalloped hammerhead populations are segregated by sex and size, with Australian populations dominated by juveniles and small adult males, while Indonesian and PNG populations included large adult females. The IAF process introduced genetic and tagging data to produce conceptual models of stock structure and movement. Several hypotheses were produced to explain stock structure and movement patterns, but more data are needed to identify the most likely hypothesis. This study demonstrates a process for assessing migratory species connectivity and highlights priority areas for hammerhead management and research.

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“…5). Both species are also known to conduct long-distance migrations [32][33][34][35][36]. These species, when cruising, swim at a rolled angle, utilizing the dorsal fin and high pectoral fin as lift-generating surfaces and thus increase their effective lift span compared to normal upright swimming.…”

Section: Discussionmentioning

confidence: 99%

Scalloped hammerhead sharks swim on their side with diel shifts in roll magnitude and periodicity

et al. 2020

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Background: Great hammerhead sharks (Sphyrna mokarran) routinely swim on their sides and periodically roll from side to side. A previous study used wind tunnel tests with a rigid model hammerhead shark to demonstrate that the rolling behavior could improve swimming efficiency using the tall first dorsal fin as a lift-generating surface. Scalloped hammerhead sharks (Sphyrna lewini) also have proportionally taller dorsal fins compared to pectoral fins than most shark species and similar to that of great hammerhead sharks, and thus might exhibit similar rolling behavior. This was assessed by deploying multi-sensor accelerometer instrument packages on free-swimming adult scalloped hammerhead sharks to directly measure swimming depth, body orientation and swimming performance. Specific objectives were to (1) determine whether scalloped hammerhead sharks exhibit side swimming and rolling behavior, (2) characterize the patterns of these behaviors, and (3) evaluate the purpose of these behaviors. Results: We obtained 196.7 total days (4720 h) of data from 9 free-swimming adult scalloped hammerhead sharks equipped with multi-instrument biologgers with deployment durations ranging from 7 to 29 days. All sharks exhibited rolling behavior throughout the entire period of observation. The roll angle magnitude and periodicity of rolling showed a clear diel pattern. During daytime, the sharks spent an average of 48% of the time swimming at a roll angle > 30°, with an average roll angle of 41° and rolling periodicity of around 4 min. At night, the sharks spent an average 82% of their time at an angle > 30°, with an average roll angle of 60° and rolling periodicity of around 13 min. In addition to an increase in degree of roll and roll duration, overall dynamic body acceleration (ODBA) also increased at night, and tailbeat frequency was more regular and consistent than during daytime. Conclusion: We observed rolling behavior in scalloped hammerhead sharks similar to that observed in great hammerhead sharks. The diel changes in roll angle and periodicity were accompanied by other changes in swimming behavior. These changes are possibly due to interplay between reducing cost of transport and social interactions with conspecifics.

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Distribution and movement of scalloped hammerheadSphryna lewiniand smooth hammerheadSphyrna zygaenasharks along the east coast of southern Africa

Cited by 38 publications

References 23 publications

Stable isotopes and elasmobranchs: tissue types, methods, applications and assumptions

Stable isotopes and elasmobranchs: tissue types, methods, applications and assumptions

Crossing lines: a multidisciplinary framework for assessing connectivity of hammerhead sharks across jurisdictional boundaries

Scalloped hammerhead sharks swim on their side with diel shifts in roll magnitude and periodicity

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