Upper Basin Kokanee & Sockeye

I don’t write much about kokanee and sockeye, but they are part of the effort to reintroduce anadromous fish into the upper Deschutes Basin.  The tribes frequently talk about the cultural significance of sockeye but they seem to be of secondary importance in reintroduction efforts.  As a fly angler who likes to target large fish, I am also very aware that kokanee are the primary food source for bull trout in Lake Billy Chinook.

Today, kokanee reside in Lake Billy Chinook, the Metolius River, and Suttle Lake.  The effort to turn these landlocked fish into ocean going sockeye has been a disappointment.  Like rainbow trout and steelhead, kokanee and sockeye are genetically similar fish, the difference is that kokanee use a lake as their “ocean”.

Since the operation of the Selective Water Withdrawal tower began in 2008, out migrations of smolts have averaged around 75,000 fish a year (ranging from 5,000 to 225,000).  The exception was 2017 when 440,000 smolts were captured at the SWW and subsequently released downstream.  Those fish should return this year as adults starting next month so there is a chance of a better return year, although early sockeye returns are down in the Columbia Basin.

It is unknown why 2017 was a good year for smolt migration but a likely cause was the huge snowpack in the Cascades that winter which resulted in high flows in the Metolius and other local rivers.  That same year saw good out migrations of steelhead and chinook smolts as well.  That being said, Kokanee populations are known to dramatically vary from year to year all over the western US.  Clearly, kokanee populations are effected by food supply, predation, and angler harvest.  Even accounting for these factors, however, the often dramatic variations in populations are not understood by biologists.

Suttle Lake and Wallowa Lake are the only two natural “nursery” lakes in Oregon, places where adult sockeye historically returned to spawn.  Of course, this ended for Suttle Lake when the Deschutes River was dammed.  For decades prior to that, however, Suttle Lake was stocked with kokanee from other lakes, degrading native fish genetics.  Today, some Suttle Lake kokanee do attempt to migrate down Lake Creek to the Metolius, presumably in an attempt to make their way to the Pacific, but essentially none of them are successful.

At last year’s Fisheries Workshop data from trapping and tagging studies was presented showing that most kokanee perish within one mile of Suttle Lake.  Only a handful of tagged Suttle Lake kokanee have ever been captured at the SWW.  (See data here.)

Lake Billy Chinook kokanee are actually genetically distinct from those in Suttle Lake.  They are the result of plantings from a variety of kokanee strains from around the Pacific Northwest.  Suttle Lake kokanee are smaller than those in LBC, although that is not saying much.  A huge LBC kokanee is only 13”.   So far, essentially all sockeye returns are from LBC smolts.  Those returns have been far lower than anticipated, averaging 45 a year (range of 23 – 98), with the exception of 536 in 2016.

By any rational measure, the attempt to reintroduce sockeye into the upper basin using resident kokanee has not been successful, as has the effort to reintroduce steelhead and chinook.  In the case of steelhead and chinook, however, changes are being made that appear to be having a positive impact.  Nighttime operation of the SWW provides an attraction flow at a time when smolts are more likely to move.  This does not seem to have helped with sockeye.  Planting of hatchery raised steelhead and chinook fry are being replaced by hatchery raised smolts.  These fish appear to have a much higher survival and capture rate at the SWW.  In addition, the plan is to use wild steelhead as hatchery broodstock if enough return to allow for that.  Why not do the same with sockeye?

Clearly, natural reproduction is superior to planting hatchery fry or smolts.  But, after giving existing kokanee a fair shot at turning into sockeye, and failing to do so, isn’t it time to modify the strategy?