Searching for sawfish in the Gulf of Carpentaria
by Barbara Wueringer, PhD Photos supplied.
In late 2015, Sharks And Rays Australia commenced a research project on the distribution and abundances of sawfish in Far North Queensland, the Cape York region and the Gulf of Carpentaria.
Sawfish were once common in coastal tropical and subtropical waters around the world, but now they are considered the most endangered family of all sharks and rays globally.
All five species of sawfish are listed on the International Union for Conservation of Nature (IUCN) Red List, three as Critically Endangered and two as Endangered, indicating that sawfish are at a high risk of extinction in the wild. Under these listings, sawfish are protected internationally to the same level as African elephants, and the trade with sawfish saws is as forbidden as the trade with ivory.
The freshwater sawfish (Pristis pristis), which is also often called the largetooth sawfish, was recently listed as one of the 100 most endangered species on the planet by the IUCN.
The best-documented decline of sawfish is the local extinction of freshwater sawfish in the waters of Lake Nicaragua in Central America. There, a commercial fishery targeting sawfish took an estimated 60,000 to 100,000 animals in five years during the 1970s.
During a scientific survey in 1992 not a single animal was caught, and in 2006 Nicaragua banned fishing for sawfish in its waters, but this move was likely decades too late.
The last assessment of the abundance and distribution patterns of sawfishes in the Gulf of Carpentaria, done by DPI’s Stirling Peverell, ended in 2008. Towards of the end of this study, sawfish received protection both under the Environmental Protection and Biodiversity Conservation (EPBC) Act and also in Queensland waters.
Scientists and managers are not clear if the protections are working, nor if sawfish are still present in sustainable numbers in the region. Because of this, Sharks And Rays Australia (SARA) has commenced its assessment in the Gulf of Carpentaria.
The Director and principal scientist of SARA, Dr Barbara Wueringer, places a high importance on working with local stakeholders including Indigenous Land and Sea Ranger groups. At this stage, SARA is in contact with four Indigenous Ranger groups along the Gulf coastline, who are helping with logistics and have received the first training on how to conduct sampling studies for sawfish.
However, the project is not possible without the help of the general public. SARA is asking people to submit information of previous sawfish captures, to better understand the distributions of the different species. Information on both tagged and untagged animals can be submitted via www.cytags.com or by calling 1800 CYTAGS (1800 298 247). Photos of sawfish are particularly welcome.
So far, SARA has received reports and video footage of live sawfish that had survived an amputation of their saw. The saw is used for feeding and enables the sawfish to sense the electric fields of its prey, allowing it to hunt in the dark and in murky waters. A saw-less sawfish will not be able to feed itself properly. Only one sawfish amputee had ever been captured by scientists and tracked for three months in Western Australia. The animal showed unusual behaviours and disappeared after three months, which likely means that it slowly starved to death.
The reproductive biology of freshwater sawfish is similar to that of sea turtles in some ways: sawfish return to the river that they were born in to give birth to their young. The pups then swim upstream and hide from predators in shallow waters. This also means that if all sawfish from one river are fished, then this river is lost to sawfish. They are very unlikely to move into a new river.
SARA’s research methods are specific by the size of animals caught, but all species of sharks and rays (which together form the group of elasmobranchs) are tagged and released. The distribution data of other species may lead to other future projects.
To find out more about SARA’s work, and how to identify sawfish, go to: http://www.sharksandraysaustralia.com
The project is currently funded by the Save Our Seas Foundation (Switzerland) and the fieldwork is made possible by the hard work and financial contributions of SARA volunteers.