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The efficacy of management interventions in response to decline in relative abundance of bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia

Bejder, L., Mann, J., Heithaus, M., Rendell, L., Hunt, H., Kobryn, H.ORCID: 0000-0003-1004-7593, Connor, R. and Whitehead, H. (2013) The efficacy of management interventions in response to decline in relative abundance of bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia. In: 20th Biennial Conference on the Biology of Marine Mammals, 9 - 13 December, Dunedin, New Zealand.


When evaluating impacts of human activities on cetaceans, adequate research design, spatio-temporal scale, and baseline data for comparative analysis are generally lacking. The current study examines changes in bottlenose dolphin abundance in Shark Bay, Australia (8855 dolphin group encounters, 1988-2011) across five consecutive ~4.5-year time periods: no dolphin-watch tourism (T0), one tour boat (T1), two periods with two tour boats (T2;T3) and lastly back to one tour boat (T4). Previously we documented a significant decline (14.9% per km2) in dolphin abundance within the tourism site compared with adjacent 36-km2 control sites when tour operations increased from one (T1) to two boats (T2) (Cons Bio 2006, Bejder et al.). Subsequently, a ministerial decision allowed both licensed operators to continue their tours, but with two primary conditions: 1) only one operator was licensed to interact with dolphins within the tourism site; the second was permitted to transit through the site to interact with dolphins outside the area; and 2) GPS “black boxes” were installed on both tour-boats, which download GPS coordinates every minute to track movements. Here, we examine dolphin abundance during T3 and T4. Using the same modelling techniques as in the original study, and 2847 additional group encounters, analyses indicate no significant change in dolphin abundance within the tourism site before (T3; +4.6% per km2; 95% CI=−5.7 to 22.2) and after (T4; -6.8% per km2; 95% CI=−27.1 to 27.3) management intervention. Four years of black box data (2007-2011; 650,000 GPS coordinates) showed a reduction in the total amount of time tour operators spent within the tourism site after management intervention (T4). Results suggest that the declining trajectory in dolphin abundance previously reported had halted during T3 (prior to management) but that the original number of dolphins present prior to tourism (T0) has not been re-established.

Item Type: Conference Item
Murdoch Affiliation(s): Centre for Fish and Fisheries Research
School of Veterinary and Life Sciences
Notes: Oral presentation
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