Solving the Salmon Puzzle in Lake Roosevelt

*This was written by Tracy Springberry and originally appeared in The Grants Messenger Newsletter*

Professor Allan Scholz, biology, has spent much of his career discovering how to keep salmon alive and well in Lake Roosevelt.

It has not been an easy problem to solve.

Before Grand Coulee Dam was built on the Columbia River in the 1930s salmon swam up rivers and streams all over the Inland Northwest to lay their eggs— about 300,000 into the Spokane River alone. The dam ended this migration by closing half the spawning grounds in the Columbia River Basin and creating Lake Roosevelt.

When Scholz arrived at Eastern Washington University in 1980 as a new assistant professor of biology, the question of how to heal that damage and return salmon to the rivers and streams above the dam, particularly into Lake Roosevelt, had not been answered.

In his quest to answer it, he has won 140 grants and contracts totaling $10.6 million, written six books and 142 other publications. He has helped establish tribal fisheries hatcheries for the Spokane, Kalispel and Kootenai tribes and a fish hatchery for the Washington Department of Fish and Wildlife at Sherman Creek near Kettle Falls. He has trained 40 graduate students and 140 undergraduates in fisheries research, effectively establishing 137 fishery scientists in the field.

Many species of salmon are born in freshwater, move to saltwater and then return to freshwater to spawn. However, some, such as the kokanee and rainbow trout, remain freshwater fish throughout their lives. Consequently, the decision was made to raise these fish in Lake Roosevelt.

Scholz and his team worked to bring kokanee salmon raised at the Spokane Tribal Hatchery on the Spokane Indian Reservation back to the WDFW Sherman Creek hatchery, which served primarily as an egg-collection facility for kokanee. They knew through the research of Scholz’s doctoral mentor that salmon know where to return to spawn, not through genetics, as was believed earlier, but by imprinting on the particular smell of a stream.

Scholz worked out when salmon imprinted on the particular odor of their stream. For kokanee this seems to happen not long after they hatch and swim up from the gravel river bottom, and again when they smolt, the time when their body prepares for living in saltwater (which happens even in kokanee). So researchers released the pre-smolt salmon in the hatchery in Sherman Creek. The salmon imprinted on the creek and later returned there to lay their eggs.

However, fewer returned than were expected. Researchers then discovered that walleye, a non-indigenous fish from the Midwest, were eating the newly released salmon. As a result, the research team stopped using Sherman Creek and started releasing pre-smolt fish into open water, which helped lower the mortality rates. However, the kokanee no longer returned to a particular stream but returned to a variety of streams along the lake.

When the Colville Tribe tried to restore natural-spawning kokanee and rainbow trout to the Sanpoil River, Scholz and his team discovered that walleye and smallmouth bass were waiting for them just as they were swimming out of the free-flowing Sanpoil River into a section that is inundated by Lake Roosevelt. In a controlled study, they discovered that in 112 days the walleye ate 94 percent of hatchery released 0.5-year-old kokanee fry, 40 percent of the 1.5-year-old kokanee smolts, 24 percent of the 1-year-old and 27 percent of the 2-year-old wild rainbow smolts. Individual walleye that had their stomachs pumped regurgitated as many as 47 kokanee!

This data led to the only real answer—reduce the walleye in the lake. After a good deal of educating the Washington Department of Fish and Wildlife, the agency has finally done something to reduce the numbers of walleye in Lake Roosevelt.

Just this month, they opened up the Spokane River Arm of Lake Roosevelt to walleye fisherman during the spawning season (formerly it had been closed to fishing during the period when walleye spawn—April 1 to May 31) and doubled the daily catch limit of walleye from 8 to 16 fish per angler.

Hopefully, these regulation changes will reduce walleye predation on kokanee and rainbow trout and also result in fatter, healthier walleye in Lake
Roosevelt.

Over the years, through many experiments and research projects, Scholz has helped increase the number of salmon that return to spawn from 0.5 percent to between 2 and 5 percent, which is the normal rate of return in a healthy system. However, he still gets discouraged when considering the long-term success of the kokanee. Each time Grand Coulee draws down quickly, it pushes fish out of Lake Roosevelt. Since one of the purposes of quick drawn downs is to stop flooding downriver in Portland and Vancouver, this probably isn’t going to end.

Still, Scholz has been actively researching this problem for 33 years, and while he is retiring from EWU next year, he plans to continue his research. He can’t quite let the problem go. He has hopes for rainbow trout, which are successfully being raised in pens for 5 to 6 months after being released from the hatchery and are already providing an excellent sport fishery for Lake Roosevelt. And while he doesn’t know if the kokanee can make it, he does have “a few more ideas” he wants to study before giving up on them completely.