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.
The die-off appears to be limited to channel catfish, officials say, and the cats have ranged in size from about 5 inches 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, Minn., was on the river Monday after a Grand Forks fisherman reported seeing dead catfish over the weekend.
The crew observed the dead catfish along a stretch of river extending from the landing in East Grand Forks and upstream for about nine miles, 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 weeks.
Some of the fish that had died more recently appeared blotchy and had lesions on their skin, Drewes said.
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Fish will be tested
The DNR crew Monday was able to capture one catfish that was just about dead, and the fish was sent to the DNR's pathology lab in St. Paul for testing, Drewes said. Results from the tests will be available sometime in the next several days.
Drewes said oxygen levels on the affected stretch of river were fine, and the water temperature was normal for this time of year. That tends to rule out "point source" pollution, such as the discharge of storm sewer water that killed fish of all species near Fargo after a heavy rainfall in the summer of 2006, Drewes said.
Instead, he said, disease or bacterial infection is the more likely culprit.
"The fact they're distributed over a wide area and just channel catfish kind of points at some kind of disease, bacterial infection or something," Drewes said. "I'm not an expert, but there are some diseases that affect catfish, and you see them on rising temperatures or dropping temperatures.
"But we'll know a lot more when we get the analysis back from the lab."
Drewes said the DNR was collaborating with North Dakota Game and Fish Department and the North Dakota Department of Health to isolate the cause of die-offs. The DNR crew on the river Monday didn't explore any farther south than about nine miles, but Lynn Schlueter, a Game and Fish Department biologist, was going to spend more time on the river Tuesday afternoon to try and find the upstream limit.
"Depending on what (Game and Fish Department) crews find, we'll know more about the extent," Drewes said. "We've had no reports downstream up toward the border."
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Angler's perspective
Karry Kyllo, a Grand Forks angler and fishing guide, said he decided to contact the DNR and Game and Fish after counting more than 300 dead fish Saturday.
Kyllo said he's been seeing dead catfish along the river south of Grand Forks for the last few weeks. He also has spotted dead catfish along the river north of Grand Forks, but said the fish could have died farther south and simply floated downstream.
The die-off also appears to coincide with a pronounced decline in fishing success over the last few weeks, said Kyllo, who logs about 75 days on the river during the open water season.
Normally, catfish anglers encounter some of the best fishing of the year in September, when the cats feed aggressively to bulk up for winter. That hasn't happened this year, Kyllo said, adding he also has noticed other signs that something's fishy, so to speak.
"I don't know if it's my imagination or not, but the fish I've been catching lately seem sluggish," Kyllo said. "We pulled in a 24-pounder here a few weeks back, and a bigger fish like that usually heads to the bottom.
"This one didn't even fight it just laid on the surface."
Despite the scope of the die-off, the DNR's Drewes said disease if that indeed turns out to be the cause typically doesn't have a long-ranging impact on fish populations.
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On the downside, managers have fewer options than they would if discharge from a sewer or factory was killing the fish.
"With bacterial infection, your hands are kind of tied," Drewes said. "But they tend to be short term and they don't tend to infect the entire population. That's the good news."
Reach Dokken at 780-1148, (800) 477-6572 ext. 148, or bdokken@gfherald.com .
