Goldfish Belong in Tanks, Not Lakes

Did you see the news this summer about huge goldfish in Keller Lake in Burnsville? A photo of a football-sized fish went viral on social media and even appeared on Good Morning America. While Keller Lake is just outside the Vermillion River Watershed, we aren’t immune from this problem. Invasive species such as goldfish and common carp have been found in small lakes and ponds within the watershed, and we’re paying close attention.

If you noticed the pictures of the goldfish in Keller Lake, they were much larger than your average fish tank’s goldfish. Goldfish size is based on their surrounding environment and their instinct for survival. Released in a lake or pond, they grow quickly and can lose their bright coloration in favor of a more natural color to avoid depredation.

The City of Lakeville and VRWJPO have been studying the water quality and habitat issues in and around East Lake. One of the main issues the lake is facing is the invasive goldfish and common carp populations. Both species are in the carp family, have similar reproduction and feeding behavior, and are very tolerant of low oxygen and poor water quality conditions. As a result, they can survive when other species of fish can’t. In fact, goldfish are able to breathe with no oxygen present in the water due to an evolutionary adaptation that allows their metabolisms to work without oxygen. This allows for goldfish populations to multiply quickly as other species will die and won’t be present to keep their population in check.

Like common carp, goldfish are bottom feeders and they stir up the lake bottom looking for food. These lake sediments contain nutrients, which when stirred up and released can create algae blooms. The resulting water clarity inhibits the growth of lake plants and creates poor habitat conditions for fish and other aquatic species. If you haven’t noticed, East Lake has been looking a little green. The City and VRWJPO are currently investing in ways to address the invasive fish populations and bring the lake into a healthier state with improved water quality.

The goldfish didn’t end up in East Lake or other local waters on their own. The release of goldfish in the lake was likely meant to be an act of compassion, but it’s in fact illegal. These fish have the ability to take over a water body quickly and the cost to control or eradicate their population is expensive, if not impossible. We strongly recommend investigating humane and responsible options for disposing of your unwanted fish, such as finding a new owner or burial.