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Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation

Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation
Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation
Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0–2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation that may also be relevant to other pelagic species.
1932-6203
e32374
Queiroz, Nuno
1b1b741e-a2ee-49c2-bbcc-2864044ba8e3
Humphries, Nicolas E.
9246d06a-396a-4c05-9721-dc340e75a4d0
Noble, Leslie R.
fed9306f-3cf1-492e-a10b-7e455e08d315
Santos, António M.
e03c26c5-2042-4eb9-92d6-39332eaf38f5
Sims, David W.
7234b444-25e2-4bd5-8348-a1c142d0cf81
Queiroz, Nuno
1b1b741e-a2ee-49c2-bbcc-2864044ba8e3
Humphries, Nicolas E.
9246d06a-396a-4c05-9721-dc340e75a4d0
Noble, Leslie R.
fed9306f-3cf1-492e-a10b-7e455e08d315
Santos, António M.
e03c26c5-2042-4eb9-92d6-39332eaf38f5
Sims, David W.
7234b444-25e2-4bd5-8348-a1c142d0cf81

Queiroz, Nuno, Humphries, Nicolas E., Noble, Leslie R., Santos, António M. and Sims, David W. (2012) Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation. PLoS ONE, 7 (2), e32374. (doi:10.1371/journal.pone.0032374).

Record type: Article

Abstract

Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0–2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation that may also be relevant to other pelagic species.

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Published date: 2012
Organisations: Ocean Biochemistry & Ecosystems

Identifiers

Local EPrints ID: 347753
URI: http://eprints.soton.ac.uk/id/eprint/347753
ISSN: 1932-6203
PURE UUID: 4c2351eb-8268-4aea-98c0-35e96931bf9d
ORCID for David W. Sims: ORCID iD orcid.org/0000-0002-0916-7363

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Date deposited: 29 Jan 2013 14:43
Last modified: 19 Jun 2024 01:44

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Contributors

Author: Nuno Queiroz
Author: Nicolas E. Humphries
Author: Leslie R. Noble
Author: António M. Santos
Author: David W. Sims ORCID iD

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