Many SULiNews readers will be aware of a recent article in Australia’s The Conversation, arguing that harvesting dugongs is cruel and that Aboriginal hunting is unsustainable (1). This article is aimed at widening the context of the debate.
‘How many are there?’ and ‘How are they doing?’ are the first questions people usually ask about species of conservation concern. These seemingly straightforward questions are tough to answer for the dugong. What we do know is that despite widespread community concerns to the contrary, dugongs are generally safer in Australia’s remote areas, where traditional hunting is the major pressure, than they are around coastal urban areas where they are impacted by habitat loss, gill netting, and vessel-strikes rather than hunting.
We don’t know how many dugongs there are globally or in Australian waters. Estimating dugong numbers is difficult because the animals mostly live in turbid water and tend to surface discreetly, often with only their nostrils breaking the surface. Our best estimates mostly come from aerial surveys combined with sophisticated statistical models. About one-fifth of the dugong’s range is in Australia. Dugong habitat extends from Shark Bay in Western Australia along 24,000 km of the northern coastline to Moreton Bay near Brisbane. Dugongs are the most abundant marine mammals in Australia’s northern coastal waters. While aerial survey data indicate more than 70,000 dugongs, the number is certainly higher. Large parts of the remote coasts of Western Australia and the Northern Territory have not been surveyed recently, or at all. The status of Australian dugongs varies greatly. Torres Strait is the world’s largest dugong habitat. Surveys conducted by researchers at James Cook University in Queensland show that the region contains a remarkable 58 per cent of the habitat, supporting high densities of dugongs in Queensland (see map).
Archaeological research indicates that dugongs have been hunted in Torres Strait for at least 4,000 years and that the harvest has been substantial since well before European settlement. Today dugong hunting is permitted under the Torres Strait Treaty between Australia and Papua New Guinea (PNG) and in Australia by the Commonwealth Torres Strait Fisheries Act and the Native Title Act. The data to compare contemporary and past catch rates are not available. The current total regional dugong catch is unknown although the Torres Strait Regional Authority is attempting to correct this deficiency for Australian communities. In 2004, our modelling suggested that the current dugong catch in Torres Strait was not sustainable. This conclusion is now questioned for several reasons:
1. Dugong habitat in Torres Strait is much more extensive than previously thought. In 2010 the first seagrass survey of far western Torres Strait discovered that this very remote region supported the largest continuous seagrass bed in Australia. A subsequent extended aerial survey established that it also supports a sizable dugong population.
2. The time series of aerial surveys conducted since the mid-1980s has not demonstrated a significant decline in dugong density in Torres Strait.
3. Studies of the diving behaviour of wild dugongs fitted with timed-depth recorders and GPS-satellite transmitters indicate that the aerial survey population estimates used in the modelling are significant underestimates.
4. Studies of hunter behaviour indicate that about two-thirds of the high density dugong habitat in Torres Strait is never hunted.
This research is being used by the Torres Strait Regional Authority in negotiations with the Papua New Guinea Government and Islander leaders regarding the management of hunting. The Authority is also working with a veterinarian to address animal welfare concerns.
In the remote Great Barrier Reef region, the dugong situation is similar to Torres Strait. However, dugongs along the urban coast have to cope with additional challenges. Analysis of the records of dugongs caught in shark nets indicated a precipitous decline in catch rates between the 1960s and 1980s. Aerial surveys since the mid-1980s indicated that the population had stabilised as a result of government management interventions. But the massive 2011 floods and cyclones reduced the dugong population to the lowest level since surveys began. Worse, the dugongs stopped breeding because of a shortage of food - no calves were seen in the region during the 2011 survey. Dugong mortalities recorded by the Queensland government’s stranding program in 2011 were the highest since comprehensive reporting began in 1998. Some dugongs migrated from the region and are now returning, but the high level of coastal development is cause for grave concern.
The most serious human impacts on dugongs along the urban coast are habitat loss, gill netting, and vessel-strikes, rather than hunting. All these impacts have associated animal welfare concerns. Concerns relating to Aboriginal hunting are accordingly misplaced. Dugong management in Australia needs to focus on much more than Indigenous hunting.
Helene Marsh is Dean of Graduate Research Studies and Professor of Environmental Science at James Cook University, Queensland.
(1) “In the name of culture: dugong hunting is simply cruel” Thiriet and Smith, The Conversation 7 April 2013, online at http://theconversation.com/in-the-name-of-culture-dugong-hunting-is-simply-cruel-12463
Photos: Below - relative density of dugongs along the coast of Queensland and adjacent Northern Territory waters based on 25 years of aerial surveys. Credit: Dr Alana Grech . Top right of page - Dugong cow and calf killed by ferry in Moreton Bay near Brisbane. Credit: Rachel Groom