Minnesota zoo tests feeding invasive goldfish to wildlife in bid to curb lake invaders

A Minnesota Zoo program in Apple Valley is piloting a conservation method that uses discarded invasive goldfish as a food source for wildlife housed at the sanctuary, in a bid to curb the spread of the fish in local waters. Officials describe the approach as experimental but promising, with early observations suggesting certain animals are adapting to the unusual diet. Kelly Kappen, a nutritionist at the Minnesota Zoo, said the team is cautiously optimistic about the initiative and is closely monitoring its effects on animal wellness and behavior as part of an ongoing evaluation.

The efforts take aim at Lake Cornelia and other Minnesota water bodies that have fallen prey to illegal “fish stocking”—the dumping of pet fish into public lakes and rivers. Goldfish that escape into the wild can grow to several pounds, undercut native species for resources, uproot aquatic plants, and spread disease. The Nine Mile Creek Watershed District has noted that the goldfish are more abundant than native fish in some affected ecosystems, and their activities disturb the lake floor, releasing nutrients that fuel algae blooms and cloud the water. The problem has prompted state and local agencies to explore ways to remove the invaders, sometimes at great logistical and environmental cost.

To address the issue, the Minnesota Zoo has formed a limited but growing partnership with Nine Mile Creek and other partners to repurpose harvested fish—including Lake Cornelia goldfish and river carp—from Minnesota waterways for use in animal care programs and wildlife sanctuaries. The approach aims to turn a waste stream into a managed food source that supports conservation goals, while reducing the volume of invasive fish entering landfills or compost facilities. In the zoo’s early tests, brown bears appear to be embracing the carp, while sea lions have shown tentative interest in the goldfish, and river otters have sampled both goldfish and rusty crayfish. “So far, brown bears are loving the carp, sea lions are tentatively enjoying the goldfish, and river otters have sampled both goldfish and rusty crayfish,” Kappen said. “We’re still learning what works best.”

The project is framed as a measured, safety-conscious effort. The zoo emphasizes that, even with promising preliminary results, any inclusion of recycled fish in animal diets must be carefully evaluated within individualized, balanced nutrition plans. Kappen said, “We are working with a limited number of partners to ensure safe food handling, and inclusion in animal diets is carefully evaluated as part of a well-balanced and individualized diet plan. Many animals are suspicious of new foods, so repeated introductions are often necessary for these new options to be consumed.” The goal is not only to address the invasive fish problem but also to safeguard animal welfare as diets evolve in response to real-world testing.

As the program develops, zoo officials hope to expand the effort as part of a broader commitment to animal wellness and environmental stewardship. The Minnesota effort has drawn attention beyond state lines, as other states have reported invasive goldfish cases in recent years. In Colorado, Nevada, and Pennsylvania, authorities have logged incidents tied to pet releases. In Erie, Pennsylvania, officials with the U.S. Fish and Wildlife Service retrieved a notably large “megalodon” goldfish from a pond, suggesting that released fish can persist and spread in ways that complicate management efforts. Officials stressed that such releases are misguided: individuals who release fish often misjudge the ecological consequences and the long-term maintenance needs involved.

The Minnesota program is positioned as a potential model for how wildlife agencies might repurpose invasive-species culls into targeted food sources for conservation animals, provided safety and nutrition considerations remain central. Critics have cautioned that using invasive-species carcasses or byproducts in animal diets carries risks that must be mitigated through strict health protocols and ongoing veterinary oversight. Proponents argue that, when executed responsibly, the approach could reduce disposal challenges and contribute to ecological restoration goals while supporting animal welfare.

In short, officials describe the initiative as an experimental, adaptive program aimed at reducing invasive goldfish pressure on Minnesota lakes and rivers, while testing a novel approach to wildlife feeding that could inform broader conversations about invasive-species management and urban-wildland interfaces. The zoo says it will continue to monitor outcomes and adjust feeding regimens as part of its broader mission of conservation, wellness, and environmental stewardship.