Big Manitoba fish make a run for the border, biologists find

For decades, Winnipeggers have headed south to Grand Forks or Fargo, N.D., in search of a deal.

Turns out, some of our biggest fish have been doing the same thing.

Biologists working on both sides of the Canada-U.S. border have found two species of fish found in the Red River — channel catfish and the carp-like bigmouth buffalo — can travel hundreds of kilometres, sometimes swimming all the way from Winnipeg to Fargo and back, possibly in pursuit of food or the perfect place to spawn.

The long-distance travels of channel cats and bigmouth buffalo are among the findings of research aimed at illuminating what happens beneath the surface of the famously muddy water in the Red River drainage basin.

Since 2010, University of Nebraska-Lincoln biologist Mark Pegg and other U.S. researchers have been implanting T-shaped tags in Red River drainage-basin catfish in the hopes anglers and commercial fishers will call a 1-800 number when they discover one of the identification markers. So far, they've tagged 15,849 fish and received about 1,100 reports about their movements.

Then in 2016, Winnipeg research biologist Douglas Watkinson and his colleagues and Fisheries and Oceans Canada started implanting transmitters in seven species of fish and installed a grid of 205 receivers on the bottom of Lake Winnipeg, the Red River and some of its tributaries.

To date, Watkinson's team has tagged 786 walleye, freshwater drum, common carp, burbot, lake sturgeon, channel cats and bigmouth buffalo — and has detected their movements about 12 million times.

The scientists, who plan to present their findings Monday evening at a seminar in Winnipeg (Victoria Inn, 6:30 p.m., free admission), say they were surprised how far channel catfish and bigmouth buffalo travel along the Red River, especially considering the obstacles the fish face at the St. Andrews Lock and Dam in Lockport, Man., and a weir at Drayton, N.D.

"Buffalo are ripping back and forth all the way to Fargo," said Watkinson, co-author of the seminal Freshwater Fishes of Manitoba.

"We're not sure why, right — if it's related to feeding, maybe some exploring and just looking for potential spawning in the future? We're not even sure if they spawn every year, at this point."

Despite their status as one of the largest fish in Manitoba — and the longest-lived freshwater fish on the planet — bigmouth buffalo are little-known in this province because they're rarely caught by anglers or commercial fishers. They can live to be 112, recently published North Dakota research says, and prefer swimming in rivers rather than lakes, Watkinson said.

Unlike carp, bigmouth buffalo are native to North America. They feed on zooplankton — tiny animals that float in the water column — rather than vegetation or fish.

Bigmouth buffalo are, however, similar to carp in that they spawn in flooded vegetation. The species could be sensitive to the loss of wetlands, Watkinson said.

His team found lake sturgeon prefer swimming around river mouths rather than open water in Lake Winnipeg, despite the species' common name, and invasive carp that spawn in Netley-Libau Marsh, at the bottom of lake, tend to spend most of the summer near the mouth of the Winnipeg River.

Watkinson's team also found that most Lake Winnipeg's walleye, the most commercially valuable fish in the world's 11th-largest lake, move from the southern basin to the northern basin rather than remain in place.

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This has big implications for the commercial walleye fishery, as some scientists had surmised there were two separate populations of walleye in the lake.

Using transmitters and receivers, the Canadian researchers also found what Pegg's team in the U.S. found by implanting identification tags: channel catfish move great distances, as well.

"My suspicion is that they're following food," Pegg said.

Catfish feed on smaller fish such as cisco and goldeye and may chase them all the way up into Lake Winnipeg's northern basin, he said.

"The extent of the movement is a bit surprising," he said. He did not expect catfish to swim 1,200 kilometres.

His said his research also helps settle the question of whether sport fishers are catching the same catfish over and over or different fish most of the time.

The data suggests there are about 1.5 million channel cats in the Red River downstream from Lockport, he said.

This too has big implications for commercial fishers, who want to harvest catfish that wind up in their nets as bycatch.

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Pegg said it's unclear what impact a commercial harvest would have on channel cats, other than it's likely Red River catfish would become smaller.