Kenai River project designed to catch information on cohos

Posted: Tuesday, September 07, 2004

By their very nature, coho salmon are an elusive bunch.

Arriving in the early fall, they return to the rivers of upper Cook Inlet after most fishers have pulled their lines and nets from the water in favor of warm homes or chilly hunting cabins. Because of their late return, cohos (or silvers, as they're more commonly known) have in the past trickled into local streams largely unnoticed by the general public.

In the past 10 years, however, that's begun to change. Instead of a few hardy anglers, the Kenai River now supports a booming sport silver fishery that's growing in popularity each year. With the increased interest in the notoriously feisty silver has come a concern on the part of the Alaska Department of Fish and Game that very little is known about how many silvers are actually out there.

A project currently being conducted by the department, however, is slowly giving biologists a picture of the overall health of the Kenai's last salmon run of the season.

"What we're trying to do is estimate how many Kenai River cohos are returning each year," said Rob Massengill, project leader for Fish and Game's silver salmon research project.

Massengill said that before the 5-year-old project began, there was essentially no information about how many silvers came back to the Kenai each year.

The department did have a project to count juvenile coho in the Moose River one of the Kenai's main silver tributaries as well as the commercial harvest that usually wraps up in mid-August. However, because nothing was known about what kind of numbers actually came into the Kenai, very little was understood about how to manage the fishery.

When the sport harvest of silvers began to take off in the early 1990s, Massengill said the department decided something had to be done to understand the size of the run before it was too late.

"There was a peak harvest in 1994 of about 100,000 sport harvested in the Kenai River," he said. "That was a peak that was kind of disconcerting."

Massengill said the last straw came in 1998, when an extremely weak return of silvers had anglers and biologists alike scratching their heads.

"What little evidence we had pointed that there might be a conservation concern on the Kenai River," he said.

The department acted to curb the harvest by lowering the daily bag limit on silvers from three fish to two, as well as restricting the season beyond the end of September. However, these regulations were based less on science than on anecdotal evidence.

Correction

"Due to a reporters error, a story in Tuesdays Clarion contained incorrect information. The Alaska Board of Fisheries was responsible for lowering the daily bag limit for silver salmon on the Kenai River from three fish to two and restricting fishing beyond the end of September.

The Clarion regrets the error."

Massengill said it was obvious there was a need to count cohos. But because silvers return to the river at the same time as sockeye and (every other year) pink salmon, the department decided it would not be feasible to try and count the fish using its traditional sonar method.

Enter the fish wheel.

The department decided the best way to get a handle on the silver run would be to what else? count the fish.

Large "fish wheels" actually large rotating traps that scoop fish from the water were installed at two spots in the Kenai. The fish wheels are the first step in a project that gives biologists an accurate count of the entire coho escapement.

Once a fish is scooped from the water, a Fish and Game technician places it in a live well. The fish is measured, checked for tags that may already have been placed in it as part of another study, then marked as having been caught. Once the data is recorded and the fish marked, it is returned to the water. The whole process takes about 25 seconds and results in little harm to the fish, Massengill said.

"We've done a lot of stuff to make (the wheels) more fish-friendly," he said.

Department employees constantly monitor the wheels, he said, which have been modified to reduce the stress placed on the fish by smoothing out rough metal edges.

Once it's set free to return to its upstream spawning run, the silver salmon is likely to never again see an employee of the Alaska Department of Fish and Game. If it does, however, that's all part of the process.

The second part of the population study involves another team of Fish and Game employees stationed a couple miles upstream from the fish wheel. Armed with a short drift gillnet, the technicians spend their days drifting downstream with their net, capturing any fish unlucky enough to get in their way.

This time of year, that means a lot of pink salmon have to be picked out of the nets. However, some coho get caught and a small percentage of these already have been caught in the fish wheel.

 

Alaska Department of Fish and Game technician Collin Hakkinen prepares to net a silver salmon as it falls from one of the department's fish wheels on the Kenai River earlier this month.

Photo by Matt Tunseth

Using a mathematical formula, the team is then able to determine what percentage of the total run was caught in the fish wheel, and from that, can get an idea of the overall run size.

"We can get a general population estimate," he said.

The fish are then released again, free to swim up tributaries and finally spawn. Massengill admitted that not all fish make it through the process. Some do die, but the department does everything it can to ensure as many of the sample fish as possible are able to continue swimming upstream, he said.

Massengill credited former Fish and Game biologist Jay Carlon with essentially designing the program currently being used on the Kenai.

"Jay really orchestrated and put this whole project together," he said.

Because of safety concerns, the Fish and Game netters use large 70-horsepower jet motors.

This has led to some concern from property owners, but Massengill said the larger motors must be used to pull the nets from snags. Without the large motors, the nets and strong Kenai current could pull the netting boat under.

"We actually had a boat sink one summer," he said.

After the coho run has wound down in late September, the department will take its newly gathered data and combine it with figures taken from the statewide sport fishing harvest survey as well as commercial fishing figures. From this, biologists can get a clear picture of exactly what's happening with the silver run.

"We've learned a lot," Massengill said. "But it's still early."

Since the study has only a few years of data compared to the decades of numbers on sockeye and chinook salmon it's still too early to draw many conclusions about how many silvers return each summer. However, preliminary estimates show that the escapement can range anywhere between 11,000 and 113,000 fish.

Eventually, he said the idea is to build long-term tables showing harvest and escapement numbers. This will enable management biologists to set up escapement ranges similar to those used for other salmon species.

"There is no in-season goal for this river right now," Massengill said.

By understanding how many fish escape each year then looking at what happens when those fish's offspring return to the river the department hopes to eventually build a management plan that can be used to stabilize coho returns over the long term.

"This is the second year we'll be able to see how much adult production results from a known escapement," he said. "We're just at the beginning."



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