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A scientific foundation for informed management decisions: Quantifying the abundance, important habitat and cumulative exposure of the Hawaii Island spinner dolphin (Stenella longirostris) stock to human activities

Tyne, Julian (2015) A scientific foundation for informed management decisions: Quantifying the abundance, important habitat and cumulative exposure of the Hawaii Island spinner dolphin (Stenella longirostris) stock to human activities. PhD thesis, Murdoch University.

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Abstract

Coastal dolphin populations are exposed to non-consumptive human activities that can pose conservation challenges. Consequently, effective management strategies, using rigorous scientific assessments of exposed populations, are needed to mitigate any potential negative impacts of these activities. To inform management decisions for the conservation of the Hawaii Island spinner dolphin (Stenella longirostris) stock, I: (i) estimated abundance and survival rates; (ii) measured the effectiveness of various sampling scenarios to detect changes in abundance; (iii) identified important spinner dolphin resting habitats; and (iv) measured cumulative exposure to human activities. Between September 2010 and March 2013, boat-based and land-based sampling was undertaken to collect dolphin photo-identification, group behaviour and acoustic data from both inside and outside four important spinner dolphin resting bays on the Kona Coast of Hawaii Island. Between years, independent survival rate estimates were similar (0.97 ± 0.05 SE), and abundance estimates of 631 (95% CI 524-761) and 668 (95% CI 556-801; CV =0.09) were very consistent. At this precision, and with 95% power and a monitoring interval of three years, a 5% change in abundance would not be detected for 12 years. I documented that should resting spinner dolphins be displaced from resting bays, they are unlikely to engage in rest behaviour elsewhere. When resting inside bays, dolphins were most likely to rest between 10:00-14:00, and over sandy substrates. Individual spinner dolphins spent between 49.5% and 69.4% of daytime resting (mean = 61.7%). Dolphins were chronically and repeatedly exposed to human activities during daytime hours (> 82% of time), with a median duration of only ten min between interactions. The short interval between interactions may prevent recovery from disturbance and deprive individuals of rest and change their sleep state from “deep” to “light”. Rest deprivation and the disruption of sleep can lead to impaired cognitive abilities and ultimately effect population viability. These data provide a firm baseline for urgent consideration by managers to evaluate the risks to the spinner dolphins of Hawaii Island, potential pathways for mitigating human interactions and ways to measure the success of management interventions.

Publication Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary and Life Sciences
Supervisor: Bejder, Lars, Loneragan, Neil, Pollock, Ken and Johnston, David
URI: http://researchrepository.murdoch.edu.au/id/eprint/27843
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