I recently saw a news item about a project to improve the water quality of Lake Nokomis in south Minneapolis. So just what does it involve? It might surprise you, but the answer to that question is carp removal.
Most everyone knows that carp are not native to North America. They are native to Eurasia where they have a long association with humans. The species has been farmed and domesticated since at least the Roman times. The common carp was popular table fair. Plus, it has a history of being a popular item in both rural and urban ponds and water gardens. Not surprisingly Koi is the same species and the goldfish is a close relative.
Many sport fish populations declined markedly in the 1800s, before harvesting regulations were implemented. That, in part, led to public pressure for the introduction and cultivation of carp in the mid-1800s. The effort involved both state and federal entities, and no doubt some independent efforts as well.
We all know the rest of this story. They were deliberately and inadvertently introduced into lakes, rivers, and streams across the country, and the carp did a little too well. By the early 1900’s they were becoming a nuisance. “Once prized, now despised” is a phrase sometimes used to describe the common carp.
Carp can significantly change the ecology of a body of water. Carp are omnivorous bottom feeders. As they feed on the plant and animal material on the bottom of the body of water they stir up the sediment. That puts more sediment in the water column which of course make the water more turbid. Predatory game fish, which are often our sport fish, are less able to see their prey. And of course, less light is available for the aquatic plants. That can mean less food and cover for many desirable aquatic animals ranging from invertebrates and fish to waterfowl. Plus, the nutrients from the sediments are released into the water which may then be taken up by algae, resulting in algae blooms. It is a cascade of events that from several perspectives is not desirable.
As for North Dakota, the common carp appears to have made it here via the Missouri River. They first showed up in the state in 1929 in the Cedar and Heart rivers, both tributaries to the Missouri. Carp can now be found in several rivers and streams across the state.
Hopefully the techniques to reduce or eliminate the carp from Lake Nokomis will work. If so, perhaps the techniques could have applicability here in North Dakota.