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How robust are estimates of coral reef shark depletion?

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dc.contributor Sch Marine & Trop Biol
dc.contributor Ctr Excellence Coral Reef Studies
dc.contributor Australian Institute Of Marine Science
dc.contributor Australian Inst Marine Sci
dc.contributor Aims Jcu
dc.contributor James Cook University
dc.contributor James Cook Univ
dc.contributor Australian Res Council CONNOLLY, SEAN R. RIZZARI, JUSTIN R. FRISCH, ASHLEY J. 2017-03-22T07:29:13Z 2017-03-22T07:29:13Z 2020-09-02T04:13:33Z 2017-03-22T07:29:13Z 2017-03-22T07:29:13Z 2020-09-02T04:13:33Z 2014-08-01
dc.identifier.citation Rizzari JR, Frisch AJ, Connolly SR (2014) How robust are estimates of coral reef shark depletion?. Biological Conservation 176: 39-47
dc.identifier.issn 0006-3207
dc.description.abstract On coral reefs, diver-surveys of shark abundance indicate that populations are severely depleted, even in no-take zones with low-levels of illegal fishing, but are protected by strictly enforced no-entry zones. These findings have been questioned, on the grounds that diver-surveys overestimate shark abundance. We evaluated whether divers encounter sharks at higher rates when they first enter the water, and whether these effects vary among reefs that are subject to different levels of human interaction due to management zoning. We also examined the consistency of abundance estimates derived from multiple survey methods. For timed-swim, towed-diver, and baited-remote-underwater-video (BRUV) surveys, encounter rates were constant over time. For audible-stationary-count (ASC) surveys, encounter rates were elevated initially, then decreased rapidly, but the extent of upward bias did not differ between management zones. Timed-swim, BRUV, and ASC surveys produced comparable estimates of shark density, however, towed-diver-surveys produced significantly lower estimates of shark density. Our findings provide no evidence for biases in diver-surveys: encounter rates with sharks were not elevated when divers first entered the water; behavioural responses of sharks were consistent across management zones; and diver-surveys yielded abundance estimates comparable to other stationary methods. Previous studies using underwater counts have concluded that sharks are vulnerable to low levels of illegal fishing in no-take management zones, and that additional measures are needed to protect species, which, like sharks, have demographic characteristics that make them vulnerable to low levels of exploitation. Our results support the robustness of the abundance estimates on which those conclusions have been based. (C) 2014 Elsevier Ltd. All rights reserved.
dc.description.sponsorship We thank M. Cappo and M. Stowar of the Australian Institute of Marine Science for loan of BRUV equipment, B. Bergseth, M. Rocker, S. Sandin and one anonymous reviewer for useful comments on the manuscript and M. Hisano for help with data analysis. This research was undertaken with permission from the Great Barrier Reef Marine Park Authority (permit no. G11/34529.1). Funding was provided by the Australian Research Council Centre of Excellence for Coral Reef Studies and the School of Marine and Tropical Biology at James Cook University. Support was also provided by a Churchill Fellowship from the Winston Churchill Memorial Trust (AJF).
dc.language English
dc.relation.ispartof Null
dc.subject Marine Reserve
dc.subject Great-barrier-reef
dc.subject Islands
dc.subject Visual Census
dc.subject Trophic Ecology
dc.subject Underwater Video Stations
dc.subject Biodiversity & Conservation
dc.subject Northern Line Islands
dc.subject Movement
dc.subject Apex Predator
dc.subject Community
dc.subject Population Assessment
dc.subject Environmental Sciences
dc.subject Density
dc.subject Populations
dc.subject Marine Park
dc.subject Environmental Sciences & Ecology
dc.subject Abundance
dc.subject Fishes
dc.subject Underwater-visual-census
dc.subject Biodiversity Conservation
dc.subject Baited-remote-underwater-video
dc.subject Ecology
dc.subject Base-lines
dc.title How robust are estimates of coral reef shark depletion?
dc.type journal article
dc.identifier.doi 10.1016/j.biocon.2014.05.003
dc.identifier.wos WOS:000340223500005

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