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New research technique puts channel catfish in spotlight

Sun., Aug. 28, 2011

The catch was the fisheries biologist’s equivalent of landing a state-record fish.

It was as memorable as discovering a new lure that catches a fish on every cast.

Idaho Fish and Game Department researchers recently caught, tagged and released more channel catfish in a single day at one lake than they’d previously surveyed in a year throughout the Panhandle region.

“We hauled in 1,200 in one set at Cocolalla Lake on (Aug. 1),” reported Mark Liter, who’s leading the North Idaho catfish survey project. “We’ve found a technique that gives us a giant leap in information to manage channel catfish.”

The tool is a hoop net, a tube-like trap that involves a series of seven rings supporting a net that stretches about 30 yards long.

The net ends are seasoned with commercial catfish bait – cheese-making byproduct and soybean cake – that lures the fish into the chambers. Restrictions prevent them from finding their way back out.

The nets were set at about 12 feet deep to avoid going below the thermocline. “Catfish can swim below the thermocline, but if they’re trapped down there they can die for lack of oxygen,” Liter explained.

The trap is set out with marker buoys and allowed to soak up to 96 hours.

In the past, the follow-up after using other netting methods could have been handled by one or two people.

But the hoop net results required help from a strong team of summer staffers.

“We’re getting up to 600 fish in a net with virtually zero mortality,” Liter said. “Just like that we’ve bumped our sample size to anywhere from 500 to 2,000 fish per lake in one shift compared with about 10 fish from a typical survey in the past.”

Fisheries researchers get much of the needed information about other species, such as trout, by doing creel surveys – contacting fishermen at take-out points on lakes and streams and asking them how many hours they fished and how many fish they caught.

“But most of the angler effort to catch catfish is at night,” Liter said. “That makes it difficult for a creel survey. We can’t really put college kids out there sitting around in the dark.”

Other standard fish surveying methods include electro-shocking – momentarily stunning fish with electric current from a boat so they can be netted, measured, tagged and released – and using various types of traps or gillnets to get a snapshot of a lake’s fishery.

But none of those methods has worked well for catfish, Liter said.

“In the past 15 years, none of our surveys methods have turned up many catfish,” he said. “Ten fish isn’t much of a sample to work with in a lake. We’ve never had a good handle on their total population.”

Catfish are olfactory hunters. “Their sense of smell is tremendous,” Liter said, noting they can pick up scent from far away boosted by the sensors in up to eight whisker-like barbels off their snouts.

“For whatever reason, using this bait and the traps made all the difference in the world,” Liter said. “We had no idea the catfish densities were this high.”

Results from the huge samples captured by the hoop nets could help Idaho fish managers lower costs and grow bigger catfish for anglers.

“Idaho spends a lot of money stocking catfish, but we know very little about their age, growth and mortality rates,” Liter said. “We spend 90 cents a fish and we’re not really sure what percentage is being caught.

“We’d like to know the return. It makes good business sense to see at least a 39 percent return to the angler to justify the expense.

“Channel catfish are not native to North Idaho. They’re extremely warm-water fish that don’t get very active until the water temperature rises above 70 degrees. They won’t initiate spawning until the temps reach 75, with the optimum being 80 degrees.”

The highest temperature researchers recorded during their July-August surveys in the catfish lakes was 74 degrees.

“And that lasted only a brief time before the lakes started cooling again in mid-August. That’s why we have to plant young catfish in Panhandle lakes.”

Channel cats are stocked off and on in up to 11 lakes on the Idaho Panhandle. Plants of 5,000-7,000 a year are scheduled for six lakes – Cocolalla, Hauser, Fernan, Jewell, Rose and Smith.

Those lakes also are stocked with rainbow trout, and they hold other species, too.

The catfish stocked the third week in June run 8-10 inches long. Fish the researchers caught this summer ranged to 24 inches long.

“I can tell you that a 22-incher is a melon of a fish,” Liter said. “Catfish fillets are great eating.

“We forget up here in North Idaho that commercial catfishing is allowed in 28 states. It’s a big deal in the southern half of the country. We don’t have the same growing conditions up here, but we can produce nice fish.”

The Panhandle region has no limit on catfish, no seasons and no size restrictions. Nevertheless, their reluctance to strike during the day has prevented channel cats from being overfished.

“We’ve learned that they are doing extremely well,” Liter said. “But we may be on the track of helping them do even better.

“We had a catfish expert from the University of Wisconsin out with us and he thought the condition of our catfish were as good as anywhere he’s seen.

“They’re not as large as they are in other states because of our growing season. They get up to about 6 pounds but we know they’re capable of 20 pounds.

“Surveys years ago turned up catfish running 12, 18 and even 20 pounds,” Liter said. The source of the hatchery-reared catfish has changed over the years, he added. “Maybe they need to look for another source with better genetics for growing larger fish.”

Or maybe the department is simply stocking too many catfish.

“Maybe we should plant fewer every year or stock every other year to get more growth,” Liter said. “We’ll be reviewing that.”

This fall, labs will be analyzing 350 samples of catfish pectoral spines to age the fish. “We removed the (fin) spine without hurting the fish,” Liter said. “In the lab, they’ll cut it with a jeweler’s saw and age it by counting the growth rings like you’d age a tree.

“My gut feeling is that we’re seeing fish in the range of 4 to 6 years.”

A yellow tag with a toll-free telephone number is attached to each fish with stainless steel wire.

Anglers give research a vital boost by calling the fish center in Boise to report their catch to the research database.

While the Panhandle region’s hoop nets have been hung up to dry for this research season, the effort’s success has caught the attention of biologists in other regions.

More channel catfish research could be under way in other areas of the state soon, Liter said.

Soon Idaho Fish and Game fish managers will have the best information yet on Panhandle channel cats, the percentage of stocked fish that are caught by anglers, how long they live, how fast they grow.

The result could be catfishing taking a spotlight in some waters, with management geared to getting the highest numbers and biggest fish possible for anglers.

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