Transforming from beloved pets to menacing monsters: The fight to eliminate giant koi from Michigan’s Glen Lake

In the crystal-clear waters of Glen Lake next to Sleeping Bear Dunes, a battle is underway to protect the ecosystem from invasive species. Robert Karner and the Glen Lake Association are leading the charge to preserve the pristine waters and native plants and animals that call this area home.

One of the invasive species causing concern is the Japanese koi, a type of carp that has been wreaking havoc in Little Glen Lake on the Leelanau Peninsula. These are not your typical domestic pond koi – they are massive „Japanese koi monsters,“ as described by Karner. The largest koi caught weighed a staggering 24.5 pounds, breaking the world record for the biggest koi caught bowfishing. Three of the four koi removed were females carrying eggs, highlighting the potential threat they pose to the ecosystem.

The presence of these invasive koi was first reported by Glen Lake residents six years ago. However, it wasn’t until preservation scientists were monitoring the spread of another invasive species, Eurasian milfoil, that they spotted the bright orange fish in drone footage. This discovery prompted Karner and his team to take action before the koi population could grow and further disrupt the balance of the lake.

To remove the koi, a unique approach was taken. Bowfishers from the Thundering Aspens Sportsman Club partnered with the Glen Lake Association and the Michigan Department of Natural Resources to catch the fast and intelligent monster fish. The bowfishers successfully removed the koi before they could reproduce, with plans to return in the following years to eliminate any remaining individuals.

Invasive species like the Japanese koi pose a significant threat to native ecosystems. They lack natural predators and are more resistant to native diseases, allowing them to outcompete and disrupt the delicate balance of the ecosystem. In the case of Glen Lake, the invasive carp are damaging native aquatic plants that provide food and shelter for native animals, ultimately impacting the clarity of the famous clear water.

Prevention is crucial in managing invasive species, as once introduced, they can be challenging and costly to control. Karner suspects that the koi in Glen Lake were once pets that were released into the lake by their owners. This highlights the importance of responsible pet ownership and the proper disposal of pets and aquarium plants to prevent further harm to native ecosystems.

In conclusion, the efforts to remove invasive koi from Glen Lake are a vital step in protecting the ecosystem and preserving the natural beauty of this area. Through collaboration and innovative approaches, like bowfishing, the Glen Lake Association and its partners are working towards a healthier and more sustainable future for this unique ecosystem.