Sections

Services

Information

UK United Kingdom

Dugongs are safer in Torres Strait than Townsville

“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 when it comes…

It’s rough out there: the waters off Townsville present many more threats to dugongs than do the hunters of the Torres Strait. Francisco Martins

“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 when it comes to the dugong.

What we do know is that dugongs are generally safer in remote areas, where traditional hunting is the major pressure, than they are around coastal urban areas where they are affected 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 our northern coastline to Moreton Bay near Brisbane. Our genetically healthy dugongs are the most abundant marine mammals in our 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. Shark Bay supports a large dugong population with minimal human pressures, making it the most secure dugong population in the world. On the other hand, the urban coast of the Great Barrier Reef (GBR) region between Cairns and Bundaberg poses many threats to dugongs.

Torres Strait is the world’s largest dugong habitat. Surveys conducted by my group at James Cook University show that the region contains a remarkable 58% of the habitat supporting high densities of dugongs in Queensland, as illustrated by the map below.

Relative density of dugongs along the coast of Queensland and adjacent Northern Territory waters based on 25 years of JCU aerial surveys. Dr Alana Grech

Archaeological research by Ian McNiven’s group at Monash 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 sanctioned by 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, I was co-author of two modelling papers using different techniques that suggested that the current dugong catch in Torres Strait was not sustainable. I now question this conclusion for several reasons:

Dugong cow and calf killed by collision with a ferry in Moreton Bay, Queensland. Rachel Groom

  • Dugong habitat in Torres Strait is much more extensive than we thought. In 2010, the Torres Strait Regional Authority partnered with scientists at Fisheries Queensland to conduct the first seagrass survey of far western Torres Strait. This survey discovered that this very remote region supported the largest continuous seagrass bed in Australia. My group subsequently extended our aerial survey of Torres Strait to cover this area and established that it also supports a sizable dugong population.

  • Our time series of aerial surveys conducted since the mid-1980s has not demonstrated a significant decline in dugong density in Torres Strait.

  • 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.

  • Studies of hunter behaviour indicate that about two-thirds of the high density dugong habitat in Torres Strait is never hunted.

James Cook University research is being used by the Torres Strait Regional Authority in negotiations with the PNG 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 GBR region north of Cooktown the dugong situation is similar to Torres Strait. However, dugongs along the urban coast of the GBR, including around Townsville, 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.

The university’s aerial surveys since the mid-1980s indicated that the population had stabilised as a result of significant management interventions by the Commonwealth and Queensland governments.

But the 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 our 2011 survey.

Dugong mortalities recorded by the Queensland government’s StrandNet program in 2011 were the highest since 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 in the urban GBR are habitat loss, gill netting, and vessel-strikes, rather than hunting. All these impacts have associated animal welfare concerns.

If you were a dugong, where would you rather live: Torres Strait or Townsville?

Sign in to Favourite

Join the conversation

7 Comments sorted by

  1. Blake Blake

    Professional

    Thank you for this article.

    Good to see someone just letting the fact speak for themselves.

    I hope this provides some perspective to the moral panic some people have tried to engender to slander Aboriginal and Torres Strait Islander hunting, including some from James Cook University I believe.

    While there are issues of animal welfare in such hunting practices, they can be addressed through respecting these people and their lifestyles and working with their communities to properly manage hunting. And a little perspective on the extent to which we cause as much harm through boat strikes, netting, pollution and habitat destruction would also be nice.

    report
  2. Jon Altman

    Research Professor in Anthropology at Australian National University

    Helene Marsh's excellent intervention in this debate makes several things quite clear. First we need a diversity of disciplinary perspectives, and especially indigenous and local and regional knowledge, to get a sensible handle on what is actually happening with dugong populations. It is to The Conservation's credit that it has sought views from a diversity of perspectives including now from a world-renown conservation biologist. Second Helene who has spent her career researching dugong is refreshingly…

    Read more
  3. Tony Simons
    Tony Simons is a Friend of The Conversation.

    Dodgy Director

    How much work has been done by pollution, dredging, seagrass loss, fertiliser and soil runoff?

    report
  4. Greg North

    Retired Engineer

    That's so good Helene to have a qualified person able to acknowledge that new information may sometimes show that what was once thought to be is not necessarily so.

    Certainly humans and associated developments will always have many impacts on nature and those living within it and it can only be hoped that more dugongs down around Townsville and other less habitat friendly neighbourhoods get the dugong tom tom message to emigrate to the Torres Strait.

    Hopefully the increased numbers will not have us next seeing dugong on broader menus.
    There was a television feature not too long back re indigenous hunting of turtles and some rather cruel callous footage shown.
    And then there was also indication of something like a booming export market developing, even some government ( possibly national parks ) aircraft being used to ship packaged turtle down to Cairns.

    report
  5. Jon Altman

    Research Professor in Anthropology at Australian National University

    Greg you got the very impression from that inflammatory 730 story about marine turtle and dugong that was the film maker's intention. It is 100% illegal for there to be any commercial trade in dugongunder Australian law. The native title rights of Aboriginal and Torres Strait Islander peoples to harvest as legally recognised under s211 of the Native Title Act is quite expicitly for 'satisfying their personal, domestic or non-commercial communal needs'. It is really important that legal harvesting for livelihood and special ceremonial occasions in the Torres Strait is not obfuscated with illegal trade. If the latter occurs no-one is suggesting that perpetrators should not be prosecuted. But to suggest that larger more robust populations of dugong will somehow provide incentive for commercial trade to occur is in the context of this debate a non sequitor.

    report
  6. Sean Lamb

    Science Denier

    If you were a dugong, where would you rather live: Torres Strait or Townsville?

    When you are young Townsville is more exciting, but Torres Strait is a better place to bring up the calves.

    report