Movements and mortality of two commercially exploited carcharhinid sharks following longline capture and release off eastern Australia

Christopher J. Barnes; Paul A. Butcher; William G. Macbeth; John W. Mandelman; Stephen D. A. Smith; Victor M. Peddemors

doi:10.3354/esr00730

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ESR 30:193-208 (2016) - DOI: https://doi.org/10.3354/esr00730

Movements and mortality of two commercially exploited carcharhinid sharks following longline capture and release off eastern Australia

Christopher J. Barnes¹, Paul A. Butcher^1,2,*, William G. Macbeth³, John W. Mandelman⁴, Stephen D. A. Smith¹, Victor M. Peddemors⁵

¹National Marine Science Centre, Southern Cross University, PO Box 4321, Coffs Harbour, New South Wales 2450, Australia
²Fisheries NSW, NSW Department of Primary Industries, National Marine Science Centre, PO Box 4321, Coffs Harbour, New South Wales 2450, Australia
³FERM Services (Fisheries and environmental consultant), PO Box 337, Sheffield, Tasmania 7306, Australia
⁴John H. Prescott Marine Laboratory, New England Aquarium, Boston, Massachusetts 02110, USA
⁵Fisheries NSW, Department of Primary Industries, Sydney Institute of Marine Science, Mosman, New South Wales 2088, Australia

*Corresponding author: paul.butcher@dpi.nsw.gov.au

ABSTRACT: Carcharhinus plumbeus (sandbar shark) and C. obscurus (dusky shark) occur in many global fisheries as targeted species and/or bycatch. However, little is known about their movement and the possible fate of discards. We redressed this lack of knowledge using pop-up satellite archival tags (PSAT) and acoustic tagging technologies off the eastern coast of Australia. Eight sharks of each species were caught by demersal longline, fitted with both types of tag and then released. PSATs indicated that 2 C. plumbeus and 1 C. obscurus died within 8 h of release, while tracks over periods of 1 to 60 d were obtained for 13 sharks. All surviving sharks first swam in an easterly, offshore direction to outer-shelf waters during the first 24 h. All C. plumbeus then moved approximately south (i.e. increasing latitude) by distances of up to ~350 km. In contrast, most C. obscurus moved approximately north by distances between 212 and 606 km. Over an 18 mo period following release, acoustic tag detections occurred for 4 C. plumbeus (mostly within 30 km of release, suggesting some philopatry) and 6 C. obscurus (~515 km south and ~310 km north). Both species spent ~85% of their time in waters <100 m deep. Diel patterns in vertical movements of C. plumbeus were detected, with a preference for deeper water during daylight hours. Both species mainly utilised water temperatures between 22 and 26°C. Information from this study can be used for the effective management of commercially exploited stocks of both species.

KEY WORDS: Carcharhinid · Satellite tag · Acoustic tag · Hook timer · Hooking mortality

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Cite this article as: Barnes CJ, Butcher PA, Macbeth WG, Mandelman JW, Smith SDA, Peddemors VM (2016) Movements and mortality of two commercially exploited carcharhinid sharks following longline capture and release off eastern Australia. Endang Species Res 30:193-208. https://doi.org/10.3354/esr00730

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ESR 30:193-208 (2016) - DOI: https://doi.org/10.3354/esr00730

Movements and mortality of two commercially exploited carcharhinid sharks following longline capture and release off eastern Australia

Christopher J. Barnes1, Paul A. Butcher1,2,*, William G. Macbeth3, John W. Mandelman4, Stephen D. A. Smith1, Victor M. Peddemors5

Christopher J. Barnes¹, Paul A. Butcher^1,2,*, William G. Macbeth³, John W. Mandelman⁴, Stephen D. A. Smith¹, Victor M. Peddemors⁵