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Goldfish on the loose in Okanagan wetlands

Goldfish and Koi  have made the news over the past few years in the Okanagan after turning up in a number of wild ponds and lakes. The fact that most aquarium fish need specific tanks, water temperatures, and food while goldfish can survive if plunked into any old container should tell you a lot about how hardy and indestructibl;e these fish are. Given enough room and food, goldfish can grow to nearly a foot long and koi can reach sizes of over 30 inches! These fish are also very long-lived in natural conditions, often living for decades. The oldest goldfish on record is 43 years old and the oldest koi ever known was scientifically proven to be over TWO HUNDRED years old. That’s a pretty long commitment...

Well-intentioned owners who no longer want their fish will sometimes release them in local creeks, ponds, or lakes, not knowing what to do with them but feeling uncomfortable about euthanizing them. This may seem like a kind deed, but it can have disastrous and cruel consequences for all other living things in that environment. Goldfish eat the eggs and larvae of our native fish and amphibians like endangered Tiger Salamanders and threatened Great Basin Spadefoots. They uproot vegetation and stir up sediment while feeding, both of which greatly reduce water quality. Goldfish can also carry diseases and parasites that can infect native fish. A single female goldfish can lay tens of thousands of eggs in one season, so two goldfish can quickly turn into a problematic invasion.

Occasionally people will release fish into stagnant water bodies as a form of mosquito control, but stagnant, fish-free ponds are very important habitat for many of our native amphibians.These water bodies often are  not actually very healthy habitat for fish either as they often get too hot in the summer, freeze solid in the winter, or even dry up completely for part of the year. Our native frogs and salamanders are used to this happening and are well adapted for it, so the drought or freezing doesn't affect them.


Here are some alternate mosquito control strategies:

  • Remove standing water from your property. Anything that holds water after a rain could be a breeding ground for mosquitos. Empty any containers with standing water at least once per week. 

  • Mosquitos have lots of natural enemies, from tadpoles and salamander larvae to birds and bats. Consider putting up bird houses or bat boxes to try and encourage mosquito predators to move in.

  • Our regional districts have ongoing mosquito control programs where pellets with a bacteria deadly only to mosquitoes are dropped into stagnant water bodies to prevent excessive numbers of mosquitoes

  •  If you have pet fish that you are no longer want, ask the pet store where you bought them if you are able to return them. If all else fails, take your fish to a veterinarian and have them humanly euthanized.

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