Bull trout and kokanee in Lake Billy Chinook


Slightly off topic for this blog, but I was frustrated with multiple fly fishing trips for bull trout at LBC this spring.  The photo is of one of my sons from last spring when big fish like this were common.  This spring they were nonexistent.  I contacted the fisheries biologists at PGE and they said they had no evidence of a population drop and shared a chart of redd spawning surveys in Metolius tributaries which continued to show a robust population.

At the PRB Fisheries Workshop I was able to talk to Mr. Bull Trout, retired biologist Don Ratliff, who said the problem was lack of algae cover on the surface of LBC.  Even though it was a low water winter, spring was cool and there was a lot of wind which blew any algae off.

Kokanee are bull trout’s primary food source and lack of cover drove the kokanee down to around 100 feet and the bull trout followed.  That’s a little deep for even the heaviest sinking fly lines.  Don said the fishing was just fine if you were trolling at that depth.

There was a presentation on kokanee populations in Suttle Lake and LBC during the conference.  They estimate that in 2017 there were about 500,000 kokanee in LBC, averaging 9 inches in length.  Perfect bull trout food.  Outmigrating anadromous smolts this spring were just not tempting enough to get the bull trout up to the surface.  It’s not in my nature to hope for algae, but I do like throwing big flies for these big fish.  They are real fighters when you hook them in the lake.

A final note on kokanee: there is also a robust population in Suttle Lake.  Kokanee can reproduce in the shallows of a lake but many of them also attempt to outmigrate by swimming down Lake Creek which connects to the Metolius River.  Essentially all of them perish in that attempt, mostly shortly after entering Lake Creek.  Over a multiyear sampling period about 750,000 kokanee left Suttle Lake but only 117 were captured at the SWW in LBC.  It is not understood why these fish perish so quickly and will be the subject of further study.  Reestablishing sockeye salmon (the anadromous variant of kokanee) is one of the objectives of the reintroduction effort.