Koi Fish Eradication Update

by | Jun 20, 2024 | Invasive Species, News

The GLA is just as committed to eradicating invasive animal species from the watershed as it is invasive plant species, and the Koi fish is no exception. Unfortunately, a number of Koi have been spotted in Little Glen Lake in recent years.

The word “koi” comes from the Japanese word for “carp,” and these fish are quite difficult to catch using traditional netting or electrofishing equipment. However, bowfishing anglers, who have studied Koi fish and are familiar with their patterns and behaviors, can safely and effectively remove the fish using bows and arrows.

The GLA has engaged a highly experienced bow fishing team from Mesick, Michigan, to attempt to remove the Koi. In May and June, four bow fishing hunts led to the removal of four Koi, including three pre-spawn females with bellies full of eggs. One female in particular set a world bow fishing record at 24.5 lbs., with the potential to produce over a million eggs per spawn.

What’s the harm in allowing this invasive fish to remain in the lake?

For starters, Koi grow to enormous size, which can cause great harm to the lake ecosystem, promote algal blooms, and lead to diminished water clarity. Their tendency to “root” is not only detrimental to the growth of native plants, but can promote invasive plants. Invasive fish also take food resources away from native fish, which are critically important to the food web and fishery in Glen Lake. Finally, Koi are prolific spawners which if left unchecked, can cause food web disruption to continue for years to come.

While there are still more Koi to be caught in Glen Lake, removing at least a few of them each year will go a long way toward eradicating the population.

Photo by Rob Karner