Some paddle boarders and rafters on the Red Deer River last summer might have noticed a foreign species that’s been lurking in the waterway since at least 2018.
That’s when an Alberta Conservation Association study confirmed the presence of carp in the Central Alberta river.
While no further studies were done in the past five years, Kevin Fitzsimmons, a fisheries biologist for the ACA, said it would be surprising if the carp population in the Red Deer River was not getting more plentiful, considering they are capable of surviving — even thriving — in less than optimal conditions.
“They are very tolerant of very poor water quality, poor habitat quality.”
He noted this prolifically reproducing foreign species will out-compete local fish for food. They will even exploit native fish for their own ends: Female carp can reproduce asexually, using the sperm of other fish species to activate egg development.
Eradicating rapacious carp from the river system would be next to impossible without also killing off a lot of native fish, Fitzsimmons added. “It would be extremely costly to get (the waterway) back to what it was.”
Trout Unlimited’s conservation director Lesley Peterson called the impact of carp on Alberta’s native fish populations “extremely disturbing.”
The Asian fish is now in most Alberta rivers, and even some in Saskatchewan. She added they have even ended up in irrigation systems in Southern Alberta. Whenever Trout Unlimited workers come across carp, they are euthanized.
Peterson’s message to Albertans who own aquariums or artificial ponds is to keep your aquatic pets out of provincial water systems or municipal storm drains that lead to rivers. “Once you let a new species in, it is very hard to take them out.”
The City of Red Deer has been grappling with this problem for several years — and is also trying to educate Red Deerians about the importance of not releasing their pets.
In 2019, city workers pulled 882 goldfish out of the Anders stormwater pond using a chemical process that would have had no effect on fish eggs. Staff realized the $250,000 project could come to nothing if somebody else puts their goldfish into the water.
Since some of the city’s retention ponds provide indirect access to the Red Deer River, utilities manager Jim Jorgensen, said city staff are trying to find a better answer. They have discussed putting netting on culverts to stop fish from going towards the river. But the mesh would have to be so tiny it would then easily plug up with leaves and other debris.
Jorgensen said city workers are now conferring with other municipalities to see how they are addressing this problem.
If physically removing the invasive fish is found to be the best solution, then the next stormwater pond to be addressed is in West Park, he added.