University of Queensland masters in zoology student Darryl Whitehead is seeking the help of Brisbane anglers to make some shocking discoveries this year.
Mr Whitehead is anxious to receive any sharks caught in the Brisbane River, and sustaining little head damage.
The sharks will be examined as a reference in a study of electro-reception, a method of detecting electrical fields used by some fish and other animals to locate their prey.
Mr Whitehead previously studied electro-reception in sharks while completing a bachelor of science in marine biology at the University of West Florida in 1996. This year he is concentrating on electrical sensitivity in fork-tailed catfish, which he says are among the most sensitive electro-receptive fishes in the world.
He plans to compare electro-reception in catfish caught in fresh, brackish and salt water. He will also study sharks caught in these environments.
'Catfish are much maligned and they're not highly regarded by anglers, but they are an extremely exciting fish - you could say a superfish,' Mr Whitehead said.
'Sensitivity tests indicate they are capable of detecting extremely minute electrical fields in the nanovolt range - about 100 billionths of a volt.
'Put another way, if you had a AA battery connected to two wires the length of a soccer field apart, they could detect that field.'
Mr Whitehead said catfish were efficient predators, despite the fact they lived in murky waters with zero visibility, often foraging (hunting) in mud at the bottom.
Cardiac monitoring of the species showed that when they detected the electrical fields of their prey, catfish could slow down their heart beats and breathing rates.
'It's a bit like a sniper, who filters out all extraneous information while concentrating on his victim,' he said.
Mr Whitehead said although many things were known about catfish in general, little study had been undertaken on the Brisbane fork-tailed catfish, Arius graeffei, a palatable white fleshed table fish, with three venomous spines, one on its back and one in each pectoral fin. The fish grows up to four kgs and a length of about 690mm.
Contact with the venom results in a sting, similar to a bee sting. Mr Whitehead says he has been stung about 500 times in the course of his study, but without major problems.
'People have to be careful filleting and handling them, but they fry up just fine like the Mississippi bullheaded catfish Ictalarus nebulosus which lives to an age of 60 to 70 years.'
Catfish also have other endearing characteristics. They communicate with each other at dawn and dusk by producing vibrations which can be heard for some distance underwater.
The croaking sounds, which have been recorded by University of Queensland marine scientists using waterproofed microphones, are made by the venom-bearing pectoral fin spines grating back and forth in their sockets. The vibrations are amplified by the fish's swimbladder, which acts like the soundbox of a guitar.
Reproduction is an interesting experience for these fish. Males fertilise the eggs, then appear to eat the clutch, storing them in their mouths, until they hatch some weeks later. Generally the males of mouthbrooding species do not eat during this period.
Dr Ian Tibbetts of the School of Marine Science and Dr Craig Franklin of the Zoology Department are supervising Mr Whitehead's studies.
Mr Whitehead said he had no difficulties catching catfish in the Brisbane River near the University's St Lucia campus, but river sharks were proving more elusive.
Anglers wishing to help with the study can contact Mr Whitehead or Dr Tibbetts, telephone 07 3365 4333, email: dwhitehead@zoology.uq.edu.au, or itibbetts@zoology.uq.edu.au
