Every two years NSW Fisheries and Queanbeyan Council release native fish into the river.

James Morgan, of Tackle World Fyshwick and a fisherman in local streams for more than 40 years, says many Queanbeyan children are catching Murray cod and golden perch in the Queanbeyan River.

"There's still a lot of redfin and carp, not so desired. But they provide a good food source for those Murray cod. Unfortunately it is outweighed by the damage the redfin do to other small fish species," Mr Morgan said.

"I have lived on the Murrumbidgee River for 11 years on the north western part of Canberra. The particular stretch of river we are in, I have only seen three redfin in that 11 years, I think it is because of that high Murray cod population. That's only speculation."

Mr Morgan says the success of stocking is evident all along the Queanbeyan River. "You can catch half-decent fish upstream from the [Monaro Street] bridge," he said.

Mr Morgan said it was less stressful releasing fish if hooked on a lure, rather than bait. People catching cod with bait should cut the line, rather than retrieve the hook from inside the fish.

"Lure fishing is best for younger ones, you are active all the time, not sitting around waiting for a bite, you are out there searching for the fish. Most lure fishermen release the fish," he said.

Queanbeyan Council's environment education officer Jennie Wetmiller says the cod fingerlings released on Friday were stained with a fluorochrome compound, calcein, which allows river monitors to distinguish between these and other fish not hatchery released.

"Previously we haven't had this so there was no way of doing any kind of count. What we see and hear from people recreational fishing, there are people fishing and catching cod within the river. " Ms Wetmiller said.

The river was in good health, Ms Wetmiller said. "One of the key indicators are platypus. If they are able to survive and flourish you know the river is doing all right."

Signs along the river bank and disposal bins will be installed to discourage people from leaving behind discarded tackle and tangled lines.

Ms Wetmiller said a swan was spotted near the shopping centre with a lure hooked in its webbed feet. "We had to go and catch it, so that is a problem we are trying to combat. we are all for the community using the river the way it was intended, but want everybody to be safe," she said.

Leaving line in the water or banks can kill or injure birds, fish and platypus and pollute the water.