The die-off appears to be limited to channel catfish, officials say, with fish ranging in size from about five to 30 inches.
According to Henry Drewes, regional fisheries supervisor for the Department of Natural Resources in Bemidji, a crew from the DNR's area fisheries office in Detroit Lakes, Minnesota, was on the river Monday after a Grand Forks fisherman reported seeing dead catfish over the weekend.
The crew observed the dead catfish all along the approximately nine-mile stretch of river they checked upstream from the landing in East Grand Forks, Drewes said. The fish were in various stages of decomposition, he said; some appeared to have died recently, while others had been dead for several days.
Some of the fish that had died more recently appeared blotchy and had lesions on their skin, Drewes said.
Biologists explore catfish kill
US - Fisheries crews from Minnesota and North Dakota are trying to find out why more than 1,600 channel catfish have died on the Red River south of Grand Forks.