The population of the Burrunan dolphin in the Gippsland Lakes at just over 90 individuals, is very small. In winter, males move into the Gippsland Lakes increasing numbers and breeding commences. Recent freshwater conditions in the Lakes are thought to have contributed to a decline in the health of the resident dolphins, with 10 confirmed or presumed deaths and a further 26 individuals not sighted during surveys. There is some evidence that this impact of fresher conditions on dolphin health and population has occurred in the past, but we do not know if and when populations will recover.
In 2011 a new species of dolphin, the Burrunan dolphin (Tursiops australis), was described from south-eastern Australia (Charlton-Robb et al. 2011). The Gippsland Lakes is home to one of only two known resident populations of this species, with an estimated resident population size of just 94 individuals (Charlton-Robb et al. 2014). During winter, however, the numbers increase, with over 1520 individuals recorded. It is thought that this is due to migration of males between the Gippsland Lakes and Tasmania in a seasonal pattern, arriving in the Gippsland Lakes in winter to breed, then heading south to Tasmania in summer. By contrast, the female population appears to be more sedentary, remaining in the Lakes year round.
Monitoring in 2021 indicated that many of the dolphins had skin lesions and up to 10 individuals were confirmed or presumed dead, with a further 26 absent from surveys. Researchers are investigating the cause of the event, but suspect that the freshwater conditions that persisted throughout the summer of 2021 may be a contributing factor. In 2007, similar freshwater conditions in the lakes led to the deaths of several dolphins and similar skin disease. This highlights the complexity of the Gippsland Lakes system and why fresher conditions are not always desirable.
Of concern are the impacts of tourism and boating on the Burrunan dolphins in the Gippsland Lakes, with the species affected by boat strike and altered behaviour from pursuit. In particular, avoidance of boats and tour operators can detract from important activities for dolphins such as feeding and resting and can lead to a decline in their health. Managing boating and tourism in the Gippsland Lakes to maintain and improve the condition of the Burrunan dolphin is important to both maintain dolphin populations and the long term sustainability of dolphin related tourism.