March 6, 2012
Sawfish Behavior Leading To Species Own Decline
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A team of researchers led by Barbara Wueringer of the University of Queensland, Australia have been studying the feeding habits of the freshwater-dwelling sawfish Pristis microdon.The researchers found that when the sawfish feeds, it uses electrosensors in its long snout to detect the location of the prey in the water. The sawfish swipes, several times per second, at its prey with a side to side motion with enough force to saw the fish in half. The sawfish would next pin the fish on the bottom of the aquarium to eat it.
Sawfishes hunt for their prey in murky waters along coastlines and in rivers. The electrosensors pick up on the minute electrical fields that fish emit while they swim in the water. The sensors allow the sawfish to locate the prey as well as to detect movements in the water.
The researchers, in this new research, simulated prey with weak electrical fields and observed the sawfish's response.
In another species of sawfish, Pristis pectinata, scientists observed the fish attacking chunks of floating “prey”, pieces of chopped mullet and tuna, They suggest that the sawfish uses its protruding snout and teeth to rake through the sand looking for buried prey, cut chunks of whales and slash at schooling fish, according to Wueringer.
Wueringer writes, “Sawfish are skilled predators but, ironically, the saw is partly to blame for their global decline: The saw is easily entangled in fishing gear, perhaps as a result of targeting prey caught in the net.”
The scientists hope that understanding the fish's response to electrical fields in the water can help to deter the fish from fishing gear that could entangle and kill the fish. “There is an upcoming field of research where people are trying to work with different electric field strengths or magnetic fields to deter animals like sharks and rays from fishing gear,” Wueringer told the BBC.
Currently the sawfish is on a decline in the wild. It is on the critically endangered list, according to the International Union for the Conservation of Nature (IUCN).
The current research is published in the March 6 issue of the journal Current Biology.
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