Extreme draining of Oregon reservoir aids young salmon and eliminates invasive fish

Statesman Journal –

A new study finds that the low-cost, extreme draining of a reservoir in Oregon aided downstream migration of juvenile chinook salmon – and led to the gradual disappearance of two species of predatory invasive fish in the artificial lake.

The study is published in the journal Ecohydrology.

The elimination of largemouth bass and crappie from Fall Creek Reservoir, about 30 miles southeast of Eugene in  the Willamette River basin, could have management implications for reservoirs that have been invaded by certain species of fish that eat other fish, according to Christina Murphy, a recent Oregon State University doctoral graduate and lead author on the study.

“Even though the strategy appears extreme, it’s both helping juvenile salmonids pass downstream and promoting a native species-dominated reservoir,” Murphy said. “Bass and crappie, which are major predators in the reservoir, have been pushed out and into the Willamette. That can be worrying because filling the river with invasive, warm-water fish seems like a bad idea, but these reservoirs are leaking warm-water fish all the time.

“The good news is that they were pushed downstream in the fall and winter, when the water is cold and the flow is faster, so they should be at a disadvantage in the Willamette River – compared to when they leak out of the reservoir in the summer.”

Read more