Prevalence of Skin Lesions and Injuries in Australian Humpback Dolphins (Sousa sahulensis) and Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Moreton Bay, Queensland

Abstract

Coastal dolphin populations are highly vulnerable due to their proximity to major urban centres and exposure to cumulative threats from anthropogenic activities. As bioindicators of environmental condition, it is crucial to understand and monitor the health of these coastal dolphin populations. Visual assessments of skin lesions on dolphins can provide useful insights into the health of these populations and exposure to environmental stressors. We examined the prevalence of skin lesions in Australian humpback dolphins (Sousa sahulensis) and Indo-Pacific bottlenose dolphins (Tursiops aduncus) of different age classes inhabiting the near-urban embayment of Moreton Bay, Queensland. The prevalence and extent of nontraumatic and traumatic skin lesions on individual dolphins were assessed using photographs taken during 103 boat-based surveys completed between 2014 and 2016. A total of 15 primary skin lesion categories were identified from 126 humpback and 100 bottlenose dolphins. Differences in the prevalence of skin lesions were evident between age classes and species. Nontraumatic skin lesions were prevalent in 48.4% of the humpback and 61.0% of the bottlenose dolphins. Comparatively, traumatic lesions were evident in almost all humpback (92.3%) and bottlenose (99.0%) dolphins. Anthropogenic-related injuries from entanglement in fishing gear and vessel strikes were substantial and significantly differed between species (p < 0.05). Injuries from fishing and vessel activities affected 11.0% of humpback dolphins and 30.0% of bottlenose dolphins, suggesting that these activities pose a major threat to these populations. Findings from this study provide an important baseline to inform ongoing health monitoring and conservation efforts of these vulnerable dolphin populations inhabiting a near-urban embayment.