Save Our Seas Foundation Archives - Sharks And Rays Australia

The saw-less sawfish?

by Barbara | Jun 17, 2016 | Blog | 0 comments

Access the original blog post written by Barbara for the Save Our Seas Foundation here.

SOSF PROJECT: SAWFISH SAFEHOUSE

BY BARBARA WUERINGER, 17 JUNE 2016

The first time I saw a sawfish, I was mesmerised. The question that sprang instantly to mind – and also the one that I get asked the most – is, what is the saw used for? To say that I found this question fascinating is an understatement, as I spent four years of my life trying to answer it. My PhD project, which I finished in 2011, focused on the feeding behaviour and sensory biology of sawfishes. And I can tell you already, the deeper I got into the topic, the more fascinating it became.

The saw is an elongation of the rostral cartilage. The elongated rostrum, which also bears lateral teeth, evolved at least three times independently in elasmobranchs: twice in rays and once in sharks – in the family Sclerorhynchidae (extinct sawfish), the family Pristiophoridae (sawsharks) and the family Pristidae (living sawfish). For my research I compared sawfishes with their close relatives the shovelnose rays of the family Rhinobatidae. As both taxa are likely to have evolved from a common ancestor that was similar to shovelnose rays, the comparison enabled me to provide a hypothesis about the evolutionary benefit of the saw in living sawfishes.

My research found that the freshwater sawfish Pristis pristis uses its saw both to sense prey (via electroreception and touching) and to manipulate it. Interestingly, juvenile freshwater sawfishes slash at an electric dipole, which resembles visually hidden prey, only when it is suspended in the water. Shovelnose rays hardly react to these fields. When a sawfish encounters an electric dipole field on the bottom, just like a shovelnose ray it tries to gobble up the field source with its mouth. These results clearly indicate that the evolution of the saw enabled sawfishes to expand their hunting strategy to include fast, free-swimming prey.

The saw, however, is also what gets sawfishes into trouble. Saws easily get entangled in fishing gear and the sawfishes wrap themselves up even more in nets when they try to escape from the invisible danger, sometimes becoming dangerous to handle. Saws are also sought-after trophies. Even though all species of sawfish are listed on CITES and the four species in Australia are protected locally under federal and state legislation, saws can still sometimes be found for sale at local markets or on e-bay.

I had always thought that fishermen were taking whole sawfishes and selling the fins separately from the saws. After all, sawfish fins are among the most valuable in the international shark-fin trade and can fetch a few thousand dollars each. But there is a different, even more disturbing practice. Fishermen, both commercial and recreational, are cutting off a captured sawfish’s saw before releasing the animal alive. Although I had heard rumours about this practice, it was only in November 2015, when we finally ran the first research expedition with Sharks And Rays Australia to the Norman River, that I started to realise just how much of an issue it could be.

Situated in the south-eastern corner of the Gulf of Carpentaria, the Norman River is a Mecca for commercial and recreational fishermen who are after barramundi. It is fairly accessible, being one of the few destinations in the Cape York region that can be reached by a paved road. Moreover, public concrete ramps enable boats to be launched easily at Normanton, which lies inland on the river, and at the coastal fishing port of Karumba.

During the closed season for barramundi fishing, the boats parked in the Karumba gardens overshadow the houses. Photo © Barbara Wueringer | Sharks And Rays Australia.

Setting, checking and retrieving gill nets in this river was an adventure. We were manoeuvring in waters with an average visibility of 10 centimetres (four inches). Hidden under the surface were landscapes of boulders, sunken logs and sand bars that were only visible with the aid of modern technology. The presence of large saltwater crocodiles took the required alertness and protocols to the next level. We had prepared for encounters with all kinds of creatures, from our study species to sand flies, mosquitoes, stingrays and stingers. What made the sampling even more difficult was that the river was full of jellyfish. Our net setting required fine-tuning.

After four days of sampling we managed to capture, tag and release one juvenile bull shark and one sawfish. I don’t think that this low sample number reflects the sawfish population of the Norman River, but it will take many more field trips to find out. As a result of our outreach efforts while we were at the Normanton Tourist Park, we received reports of two accidental sawfish captures that took place just days before we arrived. When the sawfishes were captured by recreational fishermen, the saws of both were already missing. The fishes were released alive, but their chances of survival are slim.

Can you see the crocodile's foot prints? The entrance to a hide out of a saltwater crocodile Crocodylus porosus. The belly slide is around 50 cm wide, indicating a large animal.

The entrance to a nesting site of a saltwater crocodile Crocodylus porosus. The belly slide is around 50 cm wide, indicating a large animal. Photo © David Nash | Sharks And Rays Australia

A group of pelicans - which is called a pod - in the southern Gulf of Carpenteria

A group of pelicans is called a pod! Photo © David Nash | Sharks And Rays Australia.

Together with the Save Our Seas Foundation Media Unit, the material submitted was turned into an educational video so that this sad occurrence could be turned into an opportunity for public education. Please share it widely.

Facts

In countries where sawfishes are protected, the removal of a sawfish’s saw is illegal.
As sawfishes are listed by CITES (the Convention on International Trade in Endangered Species), any international trade in sawfish body parts or live animals is regulated.
In Australia sawfish are protected under the EPBC Act.
When the saw of a live sawfish is removed, the brain cavity is opened, resulting in the sawfish’s slow, lingering death.
A sawfish uses its saw to find and manipulate its prey. It also uses it to defend itself.

Further reading
Morgan DL, Wueringer BE, Allen MG, Ebner BC, Whitty JM et al. 2016. What is the fate of amputee sawfish? Fisheries 41(2): 71–73.
Seitz JC, Poulakis GR. 2006. Anthropogenic effects on the smalltooth sawfish (Pristis pectinata) in the United States. Marine Pollution Bulletin 52: 1533–1540.
Wueringer BE, Squire LJ, Kajiura SM, Tibbetts IR, Hart NS et al. 2012. Electric field detection in sawfishes and shovelnose rays. PLOS ONE 7: e41605.
Wueringer BE, Squire LJ, Kajiura SM, Hart NS, Collin SP. 2012. The function of the sawfish’s saw. Current Biology 22: R150–R151.

The sawfish's gills are flushed with water during the work up.

Teagan Marzullo and Barbara Wueringer tag the first juvenile freshwater sawfish, Pristis pristis, captured for this study. Photo © David Nash | Sharks And Rays Australia.

SARA’s field team posing in front of a croc statue in Normanton, Queensland © David Nash | Sharks And Rays Australia.

Humble beginnings

by Barbara | Feb 23, 2016 | Blog | 0 comments

Access the original blog post written by Barbara for the Save Our Seas Foundation here

BY BARBARA WUERINGER, 23 FEBRUARY 2016

‘So what do you do?’
‘I’m a biologist. I work with sawfish.’
‘Starfish, really? How exciting!’
‘No, no, SAWFISH! You know, its body looks like a shark’s, but it also has a long saw with teeth down the sides! Do you know what I mean?’

This is a conversation I have had many times. Although I could blame this little misunderstanding on the fact that my native tongue is German, over the 12 years that I have lived in Queensland and worked with sawfish, I have come to realise that there is also another, more important reason.

Many Queenslanders have never heard of sawfish. Even fewer people are aware of the fact that northern Australia, including Far North Queensland and the Cape York Peninsula, is probably the last global stronghold for four species of sawfish. This phenomenon may be explained by the low population density and little tourism of the Cape York region. Another reason could be that the rivers and coastal regions of Cape York, which sawfish inhabit, have very poor visibility and are a prime habitat of saltwater crocodiles. Unless you accidentally catch a sawfish in your recreational fishing gear, these creatures are likely to remain hidden from you during your visit to Cape York.

For these reasons, I started thinking about setting up an organisation here in Cairns that would actively engage the public in research on the elasmobranch fauna of Far North Queensland and the Cape York region. In 2014 I embarked on a long, unmapped and rocky road through bureaucracy that greatly resembled the unsealed roads leading to our remote research sites. At the beginning of 2015, Sharks and Rays Australia (SARA) was finally incorporated and early in that year we signed a partial sponsorship deal with Polycraft Australia and Mercury for a small research vessel.

During the set-up phase, it became clear that the involvement of Indigenous Rangers in the ecological surveys run by SARA would be crucial. Over the past decade, the strong connection of Indigenous groups to their country has been formally recognised under the Native Title system, which provides Indigenous groups with exclusive or non-exclusive rights over their land. Most of the Cape York territory is now covered by a patchwork of Native Title rights. There, many Aboriginal Land Councils now run Indigenous Ranger programmes to manage their country. Indigenous Ranger groups also run Junior Ranger programmes to pass both ecological and traditional knowledge on to the next generation.

In September 2015, while SARA’s research vessel was still caught up in the process of commercial registration and therefore not yet launched, we decided to embark on our first trip to Cape York – without a boat. But even though I was impatient to begin the actual research – from a boat – Cape York did not disappoint.

Kicking up the dust on the way to Kowanyama, Cape York Peninsula. Most roads on the Cape York Peninsula are unsealed.

We were heading to Kowanyama, the largest Indigenous Community on Cape York. The community is located on the west coast of the cape, on the eastern side of the Gulf of Carpentaria, and is home to five different Indigenous language groups. The Indigenous Rangers of the Kowanyama Aboriginal Land Council are actively conducting ecological surveys and habitat restoration programmes. The drive to Kowanyama from Cairns takes about 12 hours, as most of the 600 kilometres of roads are unsealed. Along the way, we encountered lots of the unique wildlife of the Australian outback.

Termite mounds cover the dry grass landscapes of Cape York.

The yellow spotted monitor Varanus panoptes is widely distributed across northern Australia. It can attain a total length of 1.4 metres.

The first night, we camped along the Mitchell River, about 250 kilometres inland of the Coral Sea in the east and the Gulf of Carpentaria in the west. Even here, at this dry campsite in the middle of the bush, we were reminded of the presence of sharks and rays in the rivers of Cape York. Next to our camping spot, we found the carcass of what was probably a juvenile bull shark hanging in a tree. With the fillets missing, it looked as if it had been left behind by recreational fishermen. Its presence in such a dry region made us marvel at the ecological adaptations of sharks and rays.

The mummified, incomplete carcass of what was probably a juvenile bull shark hangs from a tree. In the background can be seen the small waterholes that are all that remains of the Mitchell River during the dry season.

In Kowanyama, we received a warm welcome from the local Indigenous Rangers. They provided us with first insights into their ongoing habitat restoration and ecological survey programmes and we discussed the potential of future collaborations for sawfish surveys. Now, while we are working out the details of this collaboration, we eagerly await our return to this beautiful part of the Cape York region and hope to put Kowanyama on the map with sawfish encounters for our research.

Barbara Wueringer of Sharks and Rays Australia meets Garreth Forrester, the senior ranger of the Kowanyama Indigenous Rangers to discuss collaborative work to tag and release sawfish on the western side of Cape York, Queensland, Australia.

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