Clearwater Region's weekly Chinook salmon update: May 18

The fish are finally getting to Idaho, and as such, I will try and get my updates to you no later than Wednesday in the future so you can better plan your fishing trips. 

Run Update

It seems that if there is a will there is a way.  Despite continued high flows over Bonneville Dam, counts of Chinook Salmon picked up over the last week, and many of these fish are Idaho bound salmon.  The spring run is definitely late, but we still don’t know how late it is.  Based on past year’s data, if Idaho’s spring Chinook runs (Clearwater, Rapid River and Hells Canyon) were considered to have a late run timing, over 90% of would of the fish would have passed over Bonneville Dam by now.  However, if the timing of these runs follow what occurred last year, which had the latest timing of any run we have seen since we have been monitoring PIT-tags, the run past Bonneville Dam would only be about 60% complete.  I personally think we are somewhere in between. 

Because the Chinook are starting to reach Idaho in fishable numbers, I figured it was about time I let you know what the run estimates mean as far as harvest shares go.  So, I built the table below that shows how many fish we think will reach Idaho based on counts at Bonneville Dam.  You will notice that I have two columns that show run estimates of adult Chinook Salmon that will reach Idaho.  One assumes that the run timing at Bonneville Dam is late (average late - over 90% complete), and the other assumes the run timing is similar to what we saw in 2017 (unusually late - about 60% complete).  As you can see by the numbers below, we are hoping the run is unusually late.

 

chinook_run_estimates_5-18-18
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Joe DuPont

Using the estimates above, we can calculate what our harvest shares would be based on the different run timings and how many fish we need to collect for brood.  As you can see from the table below, we still have a big range for what our harvest share will ultimately be, but we are starting to narrow in on it.  I think we can all agree that we would like to seem more opportunity than this, but we are fairly confident that enough will make it to Idaho to hold fisheries on all three of these runs.

chinook_harvest_shares_5-18-18
Creative Commons Licence
Joe DuPont

There are a couple others things we will be evaluating that could change these harvest shares.  One is just how well these fish survive as they migrate from Bonneville Dam to Lower Granite Dam.  Typically, with higher flows, survival goes down.  The other thing we will evaluate is just how well the PIT-tagged fish estimate the actual run size.  Typically, PIT-tag estimates represent about 70% of the actual run size because PIT-tags do occasionally fall out of fish and PIT-tagged fish can have a slightly higher mortality rate than those fish that were not PIT-tagged.  The 30% buffer that PIT-tag estimates give us is actually a good thing as we know that not all unharvested fish will show up at our fish traps.  This buffer is important to insure we meet our brood needs.  That being said, there have been a few years when PIT-tagged fish represented less than 50% of the actual run (this happened last year for the Rapid River run).  If this happens again, we could bump up the run estimate some which would increase our harvest share.  We can’t bump it up too much though because we still need to make sure we meet our brood needs.  We won’t be able to evaluate that until about half the run passes over Lower Granite Dam.  At that time we will have collected enough fish at the Lower Granite fish trap to make a reliable assessment.  So, stay tuned for this update. 

Fishery Update

We still haven’t documented any harvest yet.  However, over a thousand adult Chinook have passed over Lower Granite Dam in each of the past two days, so we expect to see some harvest soon.  I just talked to our creel clerk on the Clearwater River, and the flows are high a dirty with an occasional log floating by.  Flows are supposed to peak tomorrow, so I don’t expect conditions to get any better this weekend.  Flows in the Salmon River are at about 60,000 cfs and are supposed to keep climbing for the next 6 days, so I don’t expect to see much happening there for a while.  That being said, we have already trapped a Chinook at Rapid River hatchery.  Flows at Hells Canyon Dam are at about 28,000 cfs which isn’t bad.  It would not surprise me is some fish were caught below the dam over the next week.  Once fish start being harvested, I will post tables showing how many and where fish were caught.

 

That’s all I have for you today.  As I indicated to you earlier, I will try to get my updates out to you next week no later than Wednesday to help you with your planning.

Have a good weekend everybody