Biologists will introduce spring chinook.

Byline: From Register-Guard and news service reports

ROSEBURG - History will be in the making May 17 when the Oregon Department of Fish and Wildlife stocks hatchery spring chinook in Diamond Lake.

About 24,000 salmon in the 8- to 10-inch size range are to be released as part of an experimental program designed to determine whether landlocked salmon can provide a fishery in a lake overrun with tui chub.

"In the ocean, spring chinook aggressively pursue small fish like herring and sardines, so we hope they will swim after tui chub in the same way," ODFW district fish biologist Dave Loomis said. "We chose to stock the springers for this predatory behavior and hope they think the lake is a small ocean with lots of small fish to eat."

One of the goals of the experimental stocking program is to find a fish that will actively prey on chub so the return rate to the angler is higher than with the current rainbow trout stocking, Loomis said. "We know the lake has plenty of chub, and that these salmon cannot eat every last one to solve the problem long-term, but it's important to explore other opportunities for Diamond Lake anglers right now."

Diamond Lake was a premier rainbow trout fishery from 1910, when stocking began, through the mid-1990s. Tui chub were first introduced in the early 1940s when anglers used them as live bait to catch large rainbow. The chub were eradicated by the fish toxicant rotenone in 1954 after the trout fishery collapsed from the impacts of the chub. As a result of the devastation at Diamond Lake, the state made it illegal to use live fish for bait in Oregon. However, chub were again used as live bait in the 1990s and have exploded to a population in the millions. The trout fishery has since declined, and along with it, the water quality of the lake.

Loomis and other biologists will be studying the spring chinook to determine how efficient they are at feeding on tui chub. "We really don't know how these landlocked chinook are going to fare in the lake, what their growth and overall survival rates will be," Loomis said, "and we need to know what we'll get in terms of a fishery."

Diet studies will begin later this summer, continue into fall, then resume again the following two summers.

The spring chinook have been raised at Rock Creek Hatchery since October 2000 and will be released into Diamond Lake as 18-month-old smolts. They cost an average of $1.25 per fish. The same size as "legal" hatchery trout, the salmon weigh about a pound each. Landlocked salmon are considered trout under Oregon angling regulations.

Some of the fish will mature this fall and try to spawn in the lake, while most will mature the following two years. Oceangoing spring chinook average 15 to 20 pounds when they return to Oregon's rivers. Loomis predicts these landlocked salmon could grow to over 20 inches and weigh 5 to 10 pounds at maturity in a few years. The quality of the meat may also differ since the Diamond Lake chinook will have a much different diet than the oceangoing salmon.

Although ODFW biologists will intensively study the fishery, Loomis encourages anglers to catch and keep the spring chinook. "We're really interested to hear from the anglers what they think about catching and enjoying a feast on a lake-reared chinook," he said.

ODFW plans to stock Diamond Lake with 60,000 spring chinook next summer and will seek funding for another 60,000 in the summer of 2004. Other stocking plans for this summer and fall include 20,000 trophy-sized rainbow trout and 26,000 legal-sized rainbows.