DULUTH, Minn. — To rescue a troubled Lake Superior trout, Minnesota scientists need anglers — to scrape DNA off their catch.
The effort is part of a new study to figure out if years-long efforts to save the fish — wild steelhead — have been helping, or harming.
The results could pit two trout cousins — a popular, purely recreational strain and the long-established wild population — against each other.
For decades, biologists with the Department of Natural Resources have tried to restore the North Shore population of wild steelhead — rainbow trout that swim up rivers to reproduce — after overfishing depleted their ranks.
It’s a two-pronged strategy: Supplement the wild fish through stocking; and offer anglers an alternative to catch and keep by stocking a non-reproducing relative.
It’s unclear if either is working. In fact, the non-reproducing relative, known as Kamloops, could be hurting wild reproduction. The new study aims to get to the bottom of it.
DNR officials will formally announce the effort to anglers Saturday in White Bear Lake at the Great Waters Fly Fishing Expo, where trout are the cause celebre and buzz can begin to spread.
In the coming days or weeks, steelhead will squeeze into the mouths of Lake Superior tributaries, drawing throngs of anglers hoping to tangle with the hard-fighting, acrobatic trout that can grow longer than 30 inches and weigh more than 15 pounds.
Leading the outreach effort is Minnesota Steelheader, a nonprofit group that will help distribute free kits for anglers to collect scales of wild fish and send them to the DNR for DNA analysis.
Introduced in the 1880s, wild steelhead quickly adapted to Lake Superior, carving a niche as open-water predators and fueling a popular recreational fishery during successful spawning runs up rivers and streams. Anglers flocked to North Shore rivers not only for the fun of fishing, but also for the pink slabs of hearty flesh steelhead can provide.
Amid little fishing regulations, steelhead populations began to suffer by the 1950s. Rules were tightened again and again, but the fish continued to dwindle. In the 1970s, the DNR began stocking Kamloops, a separate strain of steelhead.
“The original purpose of the Kamloops program was to provide a harvest while we rehabilitated the steelhead population,” said Nick Peterson, a migratory fish specialist for the DNR in Duluth who is leading the new study.
More than 40 years later, Kamloops continue to be stocked, and wild steelhead have failed to fully rebound, despite strict regulations since 1997 that demand all wild steelhead be released. Kamloops are distinguishable from wild steelhead because before stocking each Kamloop, DNR workers clip the adipose fin, a nubby appendage between the fish’s dorsal fin and tail.
The Kamloops could be part of the problem.
Since 1999, at least six scientific papers have explored what happens when Kamloops attempt to spawn with the wild steelhead, which look and behave identically. “Those papers all suggest that when steelhead and Kamloops get together on the same spawning ground, their offspring don’t survive,” Peterson said.
While wild steelhead spawn up and down the North Shore and through the Great Lake, Kamloops are stocked only in the Lester and French rivers near Duluth. By and large, the fish return to these home rivers to spawn. However, reports of Kamloops venturing as far away as Wisconsin’s Brule River, where the wild steelhead run is legendary, are increasing.
It’s a touchy subject among the fishing community, said Davin Brandt, president of Minnesota Steelheader, which has not taken a stance on what to do if Kamloops are eventually implicated in the travails of their naturalized cousins.
“I personally have seen kamloops spawning with steelhead,” Brandt said. “So we know it is happening. But it’s a complex issue.”
Questions to answer
The extent to which dispersal and cross-breeding actually happens is unclear. The study aims to obtain DNA from non-Kamloops. For $5 per sample, scientists will be able to answer the following questions:
– Has Kamloops DNA infiltrated the wild steelhead population?
– Are the DNR-stocked wild-strain steelhead surviving and returning to rivers to reproduce?
– Are the wild steelhead caught at different rivers up and down the North Shore genetically distinct, as some studies have suggested?
If the answer to the last question is yes, the DNR might have to alter its methods of rearing and stocking wild-strain fish, all of which are currently derived from the Knife River.
“This project is very cheap and well worth it for what we’re going to learn from it,” Peterson said. In parallel, the DNR will attempt to net young fish — “as small as possible” — and analyze their DNA to see whether Kamloops are cross-breeding with wild steelhead and producing offspring that might not be surviving to a size where they’ll show up on the end of anglers’ rods.
How long the DNA collection campaign will run will depend on how many samples the DNR receives.
And if the Kamloops are implicated, would the agency decide to cease stocking Kamloops, even if that means shutting down all steelhead harvest, for at least a number of years?
“That decision’s going to be made at a higher pay grade than me,” Peterson said. “We’re not tailoring this study to any decision. We’re looking for information.”