Assessment of a data-limited, multi-species shark fishery in the Great Barrier Reef Marine Park and south-east Queensland
Journal Publication ResearchOnline@JCUAbstract
The status of five species of commercially exploited sharks within the Great Barrier Reef Marine Park (GBRMP) and south-east Queensland was assessed using a data-limited approach. Annual harvest rate, U, estimated empirically from tagging between 2011 and 2013, was compared with an analytically derived proxy for optimal equilibrium harvest rate, U-MSY(Lim). Median estimates of U for three principal retained species, Australian blacktip shark, Carcharhinus tilstoni, spot-tail shark, Carcharhinus sorrah, and spinner shark, Carcharhinus brevipinna, were 0.10, 0.06 and 0.07 year(⁻¹), respectively. Median U for two retained, non-target species, pigeye shark, Carcharhinus amboinensis and Australian sharpnose shark, Rhizoprionodon taylori, were 0.27 and 0.01 year(⁻¹), respectively. For all species except the Australian blacktip the median ratio of U/U-MSY(Lim) was <1. The high vulnerability of this species to fishing combined with life history characteristics meant U-MSY(Lim) was low (0.04-0.07 year(⁻¹)) and that U/U-MSY(Lim) was likely to be >1. Harvest of the Australian blacktip shark above U-MSY could place this species at a greater risk of localised depletion in parts of the GBRMP. Results of the study indicated that much higher catches, and presumably higher U, during the early 2000s were likely unsustainable. The unexpectedly high level of U on the pigeye shark indicated that output-based management controls may not have been effective in reducing harvest levels on all species, particularly those caught incidentally by other fishing sectors including the recreational sector.
Journal
Fisheries Research
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Volume
177
ISBN/ISSN
1872-6763
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Pages Count
12
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Publisher
Elsevier
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DOI
10.1016/j.fishres.2015.12.008