LE SUEUR COUNTY, Minn. (KEYC) - In the 1880s, carp was intentionally introduced into Midwest waters as game fish.
Fast forward nearly 140 years, carp are one of the most damaging aquatic invasive species, even here in Southern Minnesota.
In an effort to gather more data, Le Sueur County has started conducting population counts.
"They uproot vegetation, make the water really turbid and compete with native species, but we don’t know the extent of how they’re impacting the water quality. That’s why we are going to take a look at all these lakes and kind of see what’s going on,” said Environmental Specialist Holly Kalbus.
“Carp, in particular, are known to feed very deep in the sediment so 18 to 20 inches, they can dig to find food. What they do is they take in a mouthful of dirt or sediment, they sift out pieces of living things they want to eat, and then they expel the rest of it out and it creates a plume in the water,” said Project Biologist Aaron Claus.
That uproots native vegetation and offsets many shallow area lakes.
The population counts are done by trolling around near shore with an electrofishing boat.
If a fish is near, it will be temporarily stunned and float to the surface where officials can net the fish and keep it in water on the boat until they are able to properly measure the fish.
This is a common way of counting fish in a shallow water lake.
“If the population is more abundant and dense than approximately 89 lbs/acre, then that is known to cause significant water quality impacts. If it’s below that threshold, it’s typically not as tightly correlated with water quality impacts,” Claus added.
On our voyage Monday morning, we managed to find one carp.
It was large, swimming at 31½ inches and 15 pounds.
From there, these scientists can calculate how dense the population of carp is in the lake based on their size.
The larger they are, the fewer carp there are to compete with and since this was a large fish, it’s likely carp aren’t overrunning Lake Volney for now.
This project was funded through the county’s Aquatic Invasive Species Prevention Aid Fund.