Huge kokanee

Written by Dick Mason, The Observer June 28, 2010 06:03 pm
RITA CAMPBELL photo Ron Campbell of Pendleton landed this 27 3/4-inch state record kokanee June 13 at about 5:30 a.m. at Wallowa Lake.
RITA CAMPBELL photo Ron Campbell of Pendleton landed this 27 3/4-inch state record kokanee June 13 at about 5:30 a.m. at Wallowa Lake.
Salmon are puzzling aquatic creatures, but Wallowa Lake’s continuing run of record kokanee is not the stuff of mystery novels. 

Wallowa Lake is producing huge kokanee for a fundamental reason — mysis shrimp, according to Oregon Department of Fish and Wildlife Biologist Bill Knox of Enterprise. Mysis shrimp were planted in the lake in the mid-1960s to give the kokanee more to feed on and increase their numbers.

Today the shrimp planting of 4 1/2 decades ago is giving rise to a run of records that has anglers throughout the Northwest talking. Four times this year and five times since July someone has landed a state record kokanee salmon at Wallowa Lake. Ron Campbell of Pendleton netted the latest state record trophy on June 13. Campbell’s kokanee was 27 3/4 inches long and weighed, depending on the scale used, either 9 pounds 8 ounces or 9 pounds 10 ounces.

The fish is not the size of what the mythical Wallowa Lake monster is reputed to be, but it is a monster by kokanee standards. Kokanee generally are 8 to 11 inches and weigh less than a half pound.

The large kokanee in Wallowa Lake are the ones that have learned how to pick off the lake’s mysis shrimp. Not all kokanee are able to find mysis shrimp because they are extremely light sensitive. The shrimp spend the day deep in the lake and only come near the surface at night. Kokanee pick them off at dawn and dusk when the shrimp are moving up and down. These are the only times kokanee, which are sight feeders, can spot mysis shrimp.

The kokanee that miss out on mysis shrimp consume mostly plankton and aquatic insects, food sources that do not allow them to get big.

However, the introduction of mysis shrimp has had a negative effect on Wallowa Lake’s kokanee by causing a decrease in the total population. One reason is that young kokanee compete with mysis shrimp for plankton.

A second reason may be that mysis shrimp are helping lake trout, which prey on kokanee, to thrive. Biologists have not confirmed

if lake trout are having a significant impact on Wallowa Lake’s kokanee population.

Knox noted that years ago, mysis shrimp were planted in other lakes to boost kokanee populations. The plantings backfired because they caused lake trout populations to explode. The lake trout virtually wiped out the kokanee at places like Priest Lake and Lake Pend Oreille in North Idaho, Knox said. .

“It was a disaster,’’ he said.

At Wallowa Lake, though, the lake trout population has not expanded to the point that kokanee are severely impacted.

“For some reason (the decimation of kokanee by lake trout) has not happened here,’’ Knox said.

The possibility that Wallowa Lake’s lake trout could begin taking a significant toll on its kokanee exists and biologists are watching closely for this, Knox said.

Mysis shrimp were planted in Wallowa Lake in 1965 and 1966. The shrimp population began expanding at this point but did not begin having an impact on the size of kokanee until the mid-1980s when biologists began seeing 15- to 16-inch salmon.

The first state record kokanee was caught in Wallowa Lake in 1998. State record kokanee were caught again in 2000 and 2001.

The recent run of record kokanee may reflect, in part, extended periods of cold weather in recent winters. The winters sometimes left Wallowa Lake covered with ice and snow for two to three months. The ice reduced the light reaching the lake’s water in the daytime, resulting in more mysis shrimp swimming near the surface where kokanee can find them.

Mysis shrimp are sensitive to light because they have exceptionally large eyes. Their light sensitivity is so great that even moonlight keeps them from nearing the surface. Knox said that when ODFW teams sample the lake for mysis shrimp they do so only on nights when there is a new moon.

Knox is receiving phone calls from anglers in California, Idaho and Washington who are interested in fishing at Wallowa Lake because of the news of state record kokanee. He is also fielding many calls from newspaper reporters due to the record kokanee. The requests for information tax Knox’s time, but the knowledgeable and helpful biologist does not mind because the record kokanee are boosting interest in local fisheries.

“This is a good thing.’’