access the original blog post for the Save Our Seas Foundation here
The Daintree River is surrounded by lush rainforest. Photo © Barbara Wueringer | Sharks And Rays Australia
Native species of taro and freshwater mangroves fringe the shoreline. Photo © Barbara Wueringer | Sharks And Rays Australia
Our search for sawfishes in the waters of the northern parts of Queensland, Australia, certainly takes us into some very special ecosystems. Most are classified as arid bush or grassland, but recently our search took us to the Daintree, a special place that deserves its own blog post.
A bridge crosses a side arm of the Daintree. The main river can only be crossed by car ferry. Photo © Barbara Wueringer | Sharks And Rays Australia
Australia is the driest continent on earth – nearly 20% of its landscape is defined as desert – and is well known for this fact. The unique landscape of the outback and its drought-adapted fauna, such as termites, kangaroos and emus, are famous and for many people they represent the true Australia. But a large number of these species actually evolved from an ecosystem that is now restricted to the Wet Tropics in Far North Queensland – the Daintree.
The trunk of this tree is completely overgrown by a fern. Photo © Barbara Wueringer | Sharks And Rays Australia
One of six amethystine pythons that were resting in a tree above our sampling site. Photo © Barbara Wueringer | Sharks And Rays Australia
The Daintree is the oldest rainforest in the world. As the climate remained stable over millions of years in this region, many of the native plants have retained their ancestors’ ‘primitive’ characteristics. Of the 28 lineages of near-basal, or ‘primitive’, flowering plants that exist globally, 16 are found in the Daintree. The Daintree is often advertised as the place where the rainforest meets the Great Barrier Reef, so just imagine the species diversity that can be encountered within a few hundred kilometres! Saltwater crocodiles, cassowaries, tree kangaroos – these are only a few of the local flagship species.
A freshwater mangrove flowering in the Daintree, Far North Queensland. Photo © Barbara Wueringer | Sharks And Rays Australia
The name Daintree refers not only to the rainforest, but also to the river that flows through it. And this is where we went searching for sawfishes. We spent five days and nights sampling in the river, far inland where the water becomes more and more fresh. On this particular trip we did not catch any sawfishes, but we did tag and release some juvenile bull sharks. Currently, the distribution of sawfishes on the east coast of Far North Queensland and the Cape York region is considered to be patchy, but this may be because so little attention has been paid to it and sampling efforts have been incomplete.
A juvenile bull shark is carefully untangled from a gill net. Photo © Barbara Wueringer | Sharks And Rays Australia
The team from Sharks And Rays Australia works up a juvenile bull shark. © Barbara Wueringer | Sharks And Rays Australia
Locals in the tiny village of Daintree were super interested in our work and by the time we launched our boat there were 20–30 people watching us (about 20% of the population!). We also distributed our sawfish ID flyers (adapted from the Sawfish Conservation Society for Queensland; download here). Next time we come back we’ll be sure to give a public talk.
Barbara distributes our flyers in Daintree village, encouraging people to submit sawfish sightings. Photo © Amandine Bart | Sharks And Rays Australia
Read more about our recent paper in the press release by Murdoch University, which is copied below.
Murdoch researchers highlight the cruelty of amputating sawfish rostra
February 18, 2016
A Green Sawfish with its rostrum amputated (Pic: David Morgan)
The cruel act of amputating distinctive sawfish rostra for trophies should be afforded the same attention as the poaching of body parts from other endangered species like rhinos, a Murdoch University researcher has said.
Associate Professor David Morgan from the Freshwater Fish Group & Fish Health Unit said sawfish protection needed better enforcement globally and the conservation value of sawfish should be actively promoted.
Available evidence suggests sawfish die a lingering death after rostrum removal, he said in an article published in the Fisheries journal.
Their rostra – the chainsaw-shaped extension that distinguishes the fish and gives it its name – are used to sense, forage for and capture their prey of crustaceans and small fish.
“Sawfish forage on the riverbed and sense prey via the electrosensitive pores on their rostra,” explained Dr Barbara Wueringer, who co-authored the study.
“They then slash their rostrums to stun or impale their food. They also use the rostrums to protect themselves from predators.”
Professor Morgan and his team studied the behaviour of a Green Sawfish found in the Ashburton River after its rostrum had been illegally amputated. They tagged it and observed changes in movement patterns and habitat use compared to similarly sized sawfish with rostra intact.
“We found that it ranged more widely, perhaps in order to source ‘easy prey’ or avoid attacks by predators, than other tagged sawfish of a similar size with rostra intact,” he said.
“After 75 days the fish was no longer detected and may have either emigrated outside the detection range or, more likely, it will have perished because emigration occurred infrequently for other tagged sawfish of that size.”
At a later date, Professor Morgan also captured and tagged a Freshwater Sawfish with a partially severed rostrum contained in an isolated freshwater pool in the Fitzroy River.
He said it was severely emaciated and its damaged rostrum had impacted its ability to effectively forage.
“It was detected by our loggers for 10 days and not thereafter. In comparison, two other similarly sized individuals tagged in the same pool at the same time were detected for several months. This supports our assumption that the injured sawfish died in the pool.”
Professor Morgan said the decline of sawfish due to fishing pressure was exacerbated by humans removing sawfish rostra.
“This undoubtedly negatively impacts survival rates of those fish,” he added.
“Most amputations in northern Australia are from the last few decades.
“The few remaining human population centres that have sawfishes inhabiting their local waters must address this destructive phenomenon, and sawfish protection needs better enforcement globally.”
The Fisheries paper can be read here.