Dolphins, as apex predators which routinely appear at the water’s surface, are a good candidate species to serve as a bioindicator of ocean ecosystem health. In this study, we analysed black spot disease (BSD), a poxvirus-like skin disease in Tursiops aduncus, using the 30-year longitudinal data set gathered in Shark Bay, Australia. Using photographic observations, we characterised Shark Bay dolphins as being infected with BSD if at least one photograph showed a BSD skin lesion. We analysed this incidence data to determine general characteristics and demographics of the disease. We found that the average age of a BSD-infected individual is 26.6 ± 34.8 months with the average symptomatic period lasting 134 ± 35.6 days. The overall prevalence of BSD in the entire Shark Bay population is 19.26%. Upon demographic analysis, no sex difference was observed in the disease but there was a large age effect, with dolphins aged 1-2 years (yearlings) getting the disease significantly more than both younger and older calves. BSD was rare among juvenile and adult dolphins (N = 68 calves, 4 juveniles and 3 adults). We hypothesise that the lower prevalence in youngest calves (< 1 year) is due to maternal immunity, while older individuals (> 2 years) have infection-acquired immunity. The low prevalence overall in Shark Bay compared to other populations with poxvirus present is a positive indicator that environmental protections and controls are functioning well to keep the bottlenose dolphins healthy although the potential for zoonotic transmission warrants further investigation in this population.