Sawfish use Wi-Fi to find prey

THE UNIVERSITY OF WESTERN AUSTRALIA

Sawfish feed on catfish, mullet and freshwater prawns.  One strike from their saw can split a fish in half. Image: ShaunWilkinson/iStockphoto Research carried out by The University of Western Australia in an international collaboration for an aquarium fish collector based in Cairns has uncovered that, contrary to previous assumptions, a sawfish's saw can actually sense electric fields to locate and attack prey.  The discovery smashes the myth that sawfish are purely bottom feeders that use their saw to rake the sandy bottom.  It provides evidence that the fish, which develop in freshwater river systems, also feed closer to the surface. The discovery, led by UWA School of Animal Biology researcher Barbara Wueringer and published in the journal Current Biology, could help save the sawfish from extinction by providing vital information for captive breeding programs and strategies to save them from falling victim to commercial fishing nets.  Sawfish share a common ancestry with shovelnose rays and it's believed they evolved their saw-like rostrum with teeth on the outside to extend their niche in the underwater world. Once common in tropical and subtropical regions, freshwater sawfish spend their young life in river systems until they reach adulthood - about age 10 and at least three metres long - when they move into the ocean. Sawfish feed on catfish, mullet and freshwater prawns.  One strike from their saw can split a fish in half. Four species, which are protected in Australia, are found in the northern half of the country. "Despite their worldwide decline, there is an indication the population in Australia is still in good condition," Ms Wueringer said. "Officially they have never been targeted and so they are caught only as by-catch.  Unfortunately, their saws are often taken for trophies by both commercial and recreational fishers and their fins are popular in the shark fin trade." "The more we know about them the better we can protect them.  The first step might be to develop by-catch diversion strategies.  And for captive sawfish, we can make sure they get the right stimuli to survive and reproduce," Ms Wueringer said. Editor's Note: Original news release can be found here.