Brazilian invader at Clarrie Hall Dam
A NEW aquatic "cane toad" is threatening the Tweed's water supply and native fish stocks.
And apparently it is all due to a thoughtless aquarium owner.
A South American fish kept in aquariums has been found in ponds just beneath the Clarrie Hall Dam,with samples measuring 25cm (10 inches) long.
Local Southern Cross University environmental science student Kristy Young found the fish, commonly called the Brazilian pearl cichlid, or pearl eartheater because of the damage it does to the river beds.
It is thought they may have washed over the wall from an established%population inside the dam.
Senior lecturer in Fisheries Biology at the university Dr Daniel Bucher went fishing himself on Sunday to confirm the presence of the pest, while alarmed NSW Fisheries officers this week sent a staff member to net some.
"Kristy said she saw at least six more, and all adults," Dr Bucher said yesterday.
"Almost certainly someone has released them from an aquarium. Either they have released a whole bunch of them when they got too big for the aquarium or there's an established population and they can survive the winter.
"There is another feral population near Perth.
"They can do all sorts of damage. They are carnivores and have a fairly large mouth. Native fish would be prey.
"They also compete for bugs and so on with bass and perch and are aggressive towards larger native fish. They move sediment around a lot. If you've got them in a tank you can't keep plants."
Dr Bucher said laboratory tests on growth marks in the ear bones would reveal if the fish had been wild for a number of years, as they did not "put down" the growth record in the constant temperatures of aquariums.
The first part of their scientific name Geophagus brasiliensis is Latin for "earth eater" because the fish forage in the sandy bottom of rivers for small organisms and expel non-food items through the gills.
Dr Bucher said the fish were easy to breed in aquariums: "Just in a few months you can end up with a hundred. Pet shops are interested in a few, but not a hundred of them."
A council spokesperson said discussions were taking place with NSW Fisheries on the best way to eliminate the fish, but felt they were probably confined to below the dam wall. The fish have also been found by bass-fishing enthusiasts at the dam who have then posted comments on the website ausbass.com
One member called "Two-Bob" yesterday wrote that he was shocked on Tuesday to see what he thought were the banned exotic fish tilapia below the dam wall.
"How did those mongrel things get in here?" he asked.
"My guess would be they were released by some...idiot who did not want them anymore and was too lazy to find a new aquarium home or just too weak to knock their pets on the head, and instead potentially ruin an environment.
"I gave fisheries at Tweed a ring...if this is an isolated release they have the chance to pull these fish out of this pool and stop any breeding.
"Whether it's netting the whole pool or electro-fishing the pool it seems like a quick expense compared to what the cost may be if they let them breed and increase in numbers.
Pet fish websites describe Geophagus brasiliensis as a popular aquarium fish partly because it is a very attractive fish, greyish-green covered with blue-white pearly flecks. Fins are totally red or edged with red.