Don’t catch the cod!Published 20 August 2003
Freshwater Eastern Cod numbers are thought to be now in the low thousands and dwindling.
The fish is the focus of research by a team in SCU’s School of Environmental Science, calling themselves the Cod Squad. During the SCU Lismore Open Day from 10am till 3pm on Saturday, a freshwater Eastern Cod will be on display in a tank.
“Seeing one is getting to be as rare as sighting the snow leopard,” said Cod Squad member Anthony Moore, Research Fellow at Southern Cross University. “The main population is condensed in small, fragmented numbers in the Clarence River system. There are also small re-stocked populations in the Richmond River, but they may not prove be viable over time, despite many years of re-stocking."
“The problem with the Richmond system is poor habitat quality,” Mr Moore said. “With most of the catchment heavily degraded and only a few good pockets of habitat, the species are probably too heavily fragmented to maintain a self-sustaining population.”
NSW Fisheries and SCU surveys indicate that illegal fishing is a major threat to Eastern Cod survival. One reason the fish has been taken by local fishers in large numbers for years is the fish's aggressive nature. In its habitat, the Cod is top of the food chain and very territorial.
"If you're fishing a hole, you'll catch it," Gavin Butler said. "It's their downfall; you can catch the same fish three times in a day. If there are other species around, the cod will still go for the bait first. They'll eat anything they can fit in their mouths and they have quite a large mouth, so birds, lizards, snakes, mice, small marsupials, even water-birds and platypi, and other fish, including themselves. They're true survivors. They'll pounce on anything that goes past and they compete for food fiercely. I even have a picture of a cod with a cat in its mouth. The head of the cat is sticking out. Unfortunately the cod choked on it and died."
The SCU Cod Squad recently secured new funding to continue research on the species. Cathy Nock, a PhD student based at the Centre for Animal Conservation Genetics at SCU and Gavin Butler, an SCU student based at NSW Fisheries in Grafton have begun further work on the genetics and ecology of the Eastern Cod.
The team at SCU is advising fishers not to catch or keep the cod. Not only is it illegal, but it could further damage the cod's slim chance of survival. They advise anglers who accidentally catch the Cod to return them to the water immediately.
Increasing Cod numbers has also been the aim of a collaboration between NSW Fisheries, Booma Fisheries and a community group called Project Bigfish to restock the fish.
“These efforts are likely to have saved the species’ decline in many areas and re-established populations in areas they were wiped out,” Mr Moore said. “However, preliminary SCU research indicates that there may be a better way to breed and stock the fish.”
Cod Squad research suggests that genetic diversity is not being maintained during the artificial breeding process. This is likely to be caused by using too few parents, a problem flowing from the low numbers of wild fish left.
"Restocking can result in reduced genetic diversity," said Cathy. "There is also plenty of evidence worldwide to suggest that restocked fish are not as vigorous as remnant fish. We suspect the restocked Cod in the Richmond are not spawning. They just exist, dependent on restocking for their survival."
Cathy is using DNA markers to look at changes over time, the evolutionary process within the species, and the relationship of eastern cod to its nearest relatives.
"Depending on how successful the markers are, we may be able to distinguish stocked fish from remnant fish," said Cathy. "While this type of research has never been undertaken on Australian native fish, genetic markers have been used in the salmon family, to identify restocked fish, and to determine how much restocking contributes to the gene pool in the long term."
While determining genetic diversity in Cod samples collected by the team and NSW Fisheries, which includes 300 wild samples, and 100 known hatchery fish, Cathy is also comparing genetic diversity with the Murray Cod, which has a bigger range and a much bigger population.
"We have only preliminary results, but it looks as though natural levels of genetic diversity in the Eastern Cod are very low, by comparison to Murray Cod,” Ms Nock said. "Our data suggests that Eastern Cod have been through an historical population bottleneck which appears to have happened prior to documented population crashes in the early 1900’s.”
"The Cod is iconic," Mr Moore said. "Like the Barramundi in north and the Murray Cod in the south, the Eastern Cod is deeply part of the image of Australia and Australians. They are very important to Aboriginal people. Unfortunately all endemic freshwater cod are under threat. If you remove an animal that's top of the food chain, that must impact on the rest of the ecosystem. The only hope for the fish is through further research and community education."
The Biology Lab at SCU’s School of Environmental Science will be filled with displays from subject areas offered by the school: marine, geological, chemistry and forestry displays as well as post-grad research topics like the live eastern cod which will be in the tank. There will also be displays featuring SCU’s whale research and the biochemical wonderland of reed beds. Information will be available on courses from both academics and video monitors.
The Forestry Club is hosting a BBQ on the cement area outside the biology lab from 12.30.
Pic caption: Volunteer researcher and former SCU postgraduate student David Taylor with an Eastern Cod on the Mann River.
Further information: Media liaison 02 66203144 or 0418 431484