Goldfish have made the news recently in the Okanagan after turning up in a number of ponds and lakes. Those old timey images of goldfish in bags given out as prizes at the county fair should give you an idea of how hardy the common goldfish really is. If properly housed and cared for, goldfish can reach sizes of over 12 inches and the oldest goldfish on record is 43 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. This may seem like a kind deed, but it can have disastrous consequences to our environment. A single female goldfish can lay tens of thousands of eggs in one season, so two goldfish can quickly turn into a problematic invasion.
Goldfish uproot vegetation and stir up sediment while feeding, both of which reduce water quality. They eat the eggs and larvae of our native fish and amphibians like endangered Tiger Salamanders and threatened Great Basin Spadefoots. Goldfish can also carry diseases and parasites that can infect native fish. If the entire contents of a fish tank are dumped into a waterway then some of the aquarium plants also have the potential to become invasive.
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.
Goldfish on the loose in Okanagan wetlands
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 mosquitos are dropped into mosquito-filled stagnant water bodies.
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.