Profiling the genetics of the Willamette and McKenzie redside rainbow trout

The McKenzie Redside rainbow is one of the most beautiful and sought-after native fish in the Northwest. But how much have we diluted the genetics of these fish with massive hatchery programs? Where are the most pure strains of native fish in the system?

These are the questions ODFW is hoping to answer in its genetic sampling project for the Upper Willamette redside rainbow trout.

According to ODFW biologist Jeff Ziller, the idea for the project began over ten years ago when Willamette Winter Steelhead were being listed as an endangered species. The original plan from the National Marine Fisheries Service was to call every Oncorhynchus mykiss in the Willamette basin a steelhead, meaning every rainbow trout in the basin would be included in the plan.

“We didn’t think that was right, so we did some analysis to suggest there ought to be a break at the Calapooia River,” Ziller said. “Most of the lower tributaries of the Willamette Basin have steelhead, and from Albany upstream we have trout.”

ODFW collected genetic material from different stocks of steelhead and rainbow trout in the basin, and found the two strains of fish are dramatically different. The Willamette winter steelhead are genetically similar to the Columbia River strains of steelhead, while the upper basin rainbow trout are totally unique.

In fact, Ziller hypothesizes that redside rainbow trout and Willamette winter steelhead entered the Willamette and McKenzie Basins from entirely different river systems.

Our native rainbows are more closely related to fish in the Umpqua River, according to genetic sampling. “What we think is in geologic time, some kind of headwater capture or landslide turned a creek in another direction in a low spot, out past Cottage Grove,” Ziller said. “There’s a really low pass between the Umpqua and the Willamette there.”

Also, the Umpqua is the only other place that has a relative to the Oregon Chub, found exclusively in the Willamette Valley and the Umpqua, further evidence of trading of fish species between those watersheds.

Native Redside Rainbow trout face massive threats
For nearly 100 years, our native trout populations have been decimated, primarily by the very agencies we’ve appointed to protect them.

In 1963, after the completion of Hills Creek Dam, the US Fish and Wildlife service rolled out a tremendous rotenone project to remove “non-game fish” going all the way up into the tributaries of the Upper Willamette. They applied rotenone so heavily that the poison took out every fish down to Lookout Reservoir.

Oregon started planting hatchery rainbows in the McKenzie River in 1921, and we haven’t let up since. There are very few places in the entire watershed that have not been planted with hatchery fish.

According to historic accounts, a guide in 1916 took three anglers down a five mile stretch of the McKenzie River from Thompson Lane landing to the Leaburg Lake area, before the dam. They took 225 fish (limit was 75 per person at the time), and the guides didn’t take any fish less than 12 inches. There were a lot of wild fish in the Upper McKenzie basin, all naturally reproducing.

But by 1947, the wild fish population in the McKenzie was already reduced. According to creel surveys, 45% of the fish caught in those years were hatchery fish.

Today ODFW is dumping 600,000 hatchery trout into the system. And the programs have gotten worse and worse for native fish.

In the early 1980s, OFDW stocked the McKenzie four times a year, once in the lower and three times in the upper sections. “That created a spike of activity – that first week was outrageous, but by the third week the fishery wasn’t going. They’d fished them out,” Ziller said.

Today, ODFW is stocking at more regular intervals. The upper river is stocked every other week, from the fourth Saturday in April through August. That provides a constant supply of hatchery fish, which is constant competition for wild fish and constant angler pressure.

Where did the impetus for massive pellet-head production come from? You can trace it back to the 1950s and 60s, when the Army Corps of Engineers started building flood control reservoirs in the Willamette Valley. The Corps’ mitigation responsibility to replace fish lost by dams and reservoirs is funneled into fish factories. Instead of putting money into habitat, the Corps is obligated to pump out pellet-heads.

ODFW has implemented some half-hearted protections for wild trout. In 1992 the entire McKenzie turned to catch and release for all wild trout. Since 2005, ODFW has been experimenting with triploid or sterile fish to help cut down on interbreeding.

But competition for food and constant angling pressure are driving down populations of wild rainbows nonetheless, especially on the middle section of the McKenzie River.

“If we were going to do something that would bolster the wild trout in the McKenzie River, we would probably not release summer steelhead and salmon on top of them, and we would for sure not release rainbow trout,” Ziller said. “You’re going to have a lot of injury to the wild population in that section of river. Are you going to damage that population irreparably? Probably not. We’ve got native populations in other sanctuary areas that could reinvade if we ever do decide to change the policy there.

“It’s not a life and death situation right now,” Ziller said. “It’s a depressed population – and there’s a reason for it. There’s a lot of impact. It’s a sacrifice area right now for people that want to utilize the steelhead, salmon and hatchery trout.”

Rays of hope for native rainbows
Despite the depressed populations of native redsides in the most heavily used sections of the McKenzie River, there are strongholds of mostly pure genetic native fish.

The Upper McKenzie above Blue River is the best section where there is the least amount of hatchery rainbow interaction. There was also historically very little trout stocking below Armitage park on the lower river.

“I wouldn’t want to call that section of river pristine, but there is a lot of habitat down there and there are a lot of rainbows. That is one of our best chances for native redsides,” Ziller said.

ODFW now has funding to determine the genetic characteristics of all of the rainbow trout in the Upper Willamette Basin. Ziller said this data will provide the baseline information for ODFW’s management decisions in the future.

The team at the Caddis Fly and several other guides and organizations are helping ODFW collect genetic material from native trout by taking a small clip off the ventral fin of wild trout. The volunteers are putting the small clippings in numbered vials which ODFW is sending off to a US Fish and Wildlife lab for analysis.

One project that has Ziller excited is the possibility of improving the viability of rainbow trout above Hills Creek Reservoir. The wild fish above Hills Creek are largely interbred Cape Cod strain hatchery fish that have gone back to the wild (after the 1960s rotenone dump). The populations aren’t as robust as the Upper McKenzie where the population is more genetically pure and fish are more adapted to that specific watershed.

Ziller said it’s possible that in certain areas of the Upper Middle Fork Willamette, ODFW could reintroduce the fry or eggs from a wild stock identified by the genetic analysis, and the native strain fish would out-compete planter strain rainbows, and expand the range of the redside.

This article was based on a presentation Ziller gave at a Trout Unlimited meeting in January 2009.

-Matt Stansberry