Spotty data shows flathead catfish are invasive in the Great Lakes. Image: Eric Engbretson, U.S. Fish and Wildlife Service
By Whitney McDonald
Information about flathead catfish missing from historical Great Lakes databases has aquatic organism researchers curious about when the fish emerged in this region.
“As I was putting together information about its (the flathead catfish) distribution I noticed some strange things happening up in the Great Lakes,” said Pam Fuller, a researcher with the United States Geological Survey in Gainesville, Florida.
“I decided to delve in more to figure out what was going on,” said Fuller, who manages a data base of over a thousand species worldwide, including fish, crustacean, mollusks and plants. Her flathead catfish research brought her to examine the Great Lakes region.
The results of her look at the invasion of flathead catfish into the Great Lakes were reported recently in the Journal of Great Lakes Research.
Pam Fuller
A flathead catfish is a brown and yellow fish that can weigh more than 50 pounds, according to the Michigan Department of Natural Resources. It is most likely to be seen at night when it si looking for prey.
Flathead catfish began making their way into Great Lake basins in the 1920s, the study found. The first discovery in the Great Lakes region was in the Kalamazoo and Grand rivers, which drain into Lake Michigan.
The flathead catfish is native to Mississippi, Missouri, Ohio, Tennessee, Arkansas and Rio Grande river drainages.
The study examined Michigan surveys, reports and stocking efforts along with historical and recent literature, Fuller said.
It found when, where and how many flathead catfish came to the Great Lakes region. In some years the data was sparse.
“There was a time frame where there was just no information,” Fuller said.
Some of the data showed only a few fish in certain locations. For example, only one flathead catfish was recorded in 1953 in Wolf Lake, Wisconsin, the study said.
The study found that fish stocking in the late 1800s could be responsible for first introducing the fish into Great Lakes waters.
It could have been an undocumented state stocking of fish or a private undocumented stocking, the study said. No records were found to verify this during the study.
Between 2000 and 2010 the study found that there were 10 fish stockings not approved by the state. Before then, the flathead catfish was found in 20 tributaries, the study reports. They are now in 24 tributaries.
Flathead catfish are difficult to find in waterways because they like to be in deep water, in holes and hidden under debris, the study said.
The research has not found any direct harm in the Great Lakes from the invasive fish, but their presence elsewhere has resulted in the decline of native fish. They have huge impacts in other areas in the country where they have been introduced primarily the along Atlantic coast, Fuller said.
A study by the Journal of the Southeastern Associated Fish and Wildlife Agencies found that native fish such as the brown bullhead, redbreast sunfish, largemouth bass and spotted bullhead populations have decreased since the introduction of flathead catfish. Young sturgeons are also becoming prey to the flathead catfish which is interrupting restoration programs.
Similar impacts could potentially reduce native fish in the Great Lakes if flathead catfish populations are not managed, Fuller said.
There are plans to control the movement of the fish in rivers to protect the lakes as they continue to head north. Electric barriers have already been implemented in some rivers.
“It’s not going to be feasible in the Great Lakes but these things are primarily in the rivers and the lakes adjacent to the Great Lakes,” Fuller said. “So electrification could work in the mouths of the rivers.”