Contrasting patterns of residency and space use of coastal sharks within a communal shark nursery
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Young blacktip reef sharks are often in the shallows at low tide.
Photo: Manu San Felix.
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Beverly Oh
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Predicting occurrence of juvenile shark habitat to improve conservation planning
Despite the rapid expansion of marine protected areas (MPAs) globally, the paucity of shark-monitoring data ...read more
CITATION
Oh BZL, Thums M, Babcock RC, Meeuwig JJ, Pillans RD, Speed C, Meekan MG. 2017. Contrasting patterns of residency and space use of coastal sharks within a communal shark nursery. Marine & Freshwater Research.
ABSTRACT
The benefits of marine protected areas are difficult to estimate for mobile species, but their effectiveness can be increased if essential habitats, such as nursery areas, are protected. In the present study we examined movements of juvenile blacktip reef (Carcharhinus melanopterus) and sicklefin lemon (Negaprion acutidens) sharks in a coastal nursery in northern Australia. Telemetry-derived data were modelled using Brownian bridges and overlaid with maps of habitats and no-take zones. Juvenile N. acutidens were typically residents (≥30 days) of the nursery with small areas of core space use (<1.9 km2), whereas juvenile C. melanopterus were non-residents (<30 days) and used larger areas (<5.6 km2). Both species exhibited positive selection for sandflats and mangroves, and avoidance of deeper lagoonal and slope habitats. Monthly patterns were examined only for resident N. acutidens, and residency decreased with increasing shark length and varied seasonally for males but not females. Space use showed weak declines with increasing tidal range, and slight increases with mean air pressure, rainfall and shark length. Protecting sandflat and vegetated habitats may increase the efficacy of no-take zones for juvenile N. acutidens, because they exhibit residency and affinity to these features. Conversely, such protection will be of limited benefit for juvenile C. melanopterus, because they exhibit low residency and broader movements.
FUNDING & ACKNOWLEDGEMENTS
Receiver data were sourced as part of the Integrated Marine Observing System (IMOS), supported by the Australian Government through the National Collaborative Research Infrastructure Strategy and the Super Science Initiative. The authors thank the Australian Institute of Marine Science for environmental data and S. Wijeratne (University of Western Australia, UWA) for tidal height predictions. The authors also thank numerous volunteers who supported shark tagging efforts and extend special thanks to Peter Barnes and Frazer McGregor for logistical support. Beverly Z. L. Oh was supported by a UWA postgraduate scholarship and a Holsworth Wildlife Research Endowment grant (RA/1/411/59). Funding for field work was also provided by the Save our Seas Foundation. The authors thank R. Fisher and other group members for their valuable advice on analysis.