Chinook Salmon update for the Middle Fork Clearwater River (6/20/19)

Hi Everybody.  The Middle Fork Clearwater River Chinook Salmon fishery has been open a week now (it opened 6/13/19), so I figured it was about time I provided you all an update on how this fishery was going.  If you need a reminder of what the rules for this fishery are, you can refer to my previous blog (dated 6/13/19).

During our creel surveys last week, we estimated over four days (Thursday through Sunday) that 18 adult Chinook Salmon were harvested.  Effort was relatively light but picked up some over the weekend to the point that many of the pullouts near nice looking holes had anglers parked at them.  For those who participated in this fishery, catch rates were tough averaging about 44 hours/fish.  That is about what I expected as most people are new to this fishery, and in reality, there are not a ton of fish migrating through.

The most frequent question I am getting now is “will the fishing get better?” and “how long before the fish pass through the fishery?”.  To help answer these questions, I have put together the table below.  This table shows all the PIT tagged spring Chinook Salmon that are destined for the Middle Fork Clearwater River that have been detected passing over Lower Granite Dam.  If you study this table, you will see that there are 32 of these PIT tagged fish.  Of these fish, 19 have been detected at the PIT tag array in the Selway River.  Using simple math (19/32), that tells us that as of today (6/20/19) 60% of the spring Selway run has already passed through the Middle Fork Clearwater River.  However, PIT tag arrays in rivers do not pick up all fish that swim by which means it is more likely that 70-90% of the run has probably migrated by.  As a reminder, these PIT tags represent only the spring run.  There are also some summer run fish that will be migrating through, although much fewer than the spring run (Spring run ~ 1300 fish; Summer run ~ 200 fish).  So my answer to you is that I wouldn’t expect the fishing to get better this week, but if you are looking for an excuse to go camping, hang out on a river, and potentially catch a salmon, this may be just the ticket for you.

travel_times_lgd_to_selway
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Joe DuPont

For those of you who have been studying this table, you probably have noticed some interesting things.  For example, notice how those fish that arrived at Lower Granite Dam earlier took considerably more time to migrate to the Selway River than those fish that arrived later.  The distance from Lower Granite Dam to where the Selway PIT tag array is located is about 140 miles.  Those fish that passed over Lower Granite Dam in May took on average 20 days to make this journey averaging 7 miles a day whereas those that passed over in June took 7 days on average which means they were swimming 20 miles a day.  A couple fish made the journey in 5 days swimming 28 miles a day!  What this shows me is just how much flow effects migration rates.  In May, flows in the Clearwater River exceeded 40,000 cfs for most of the time whereas in June flows steadily dropped to where they are less than 20,000 cfs now.  Another interesting thing to noticed is how these fish have been passing over Lower Granite Dam for over a month, but the vast majority have only showed up in the Selway River in the last 10 days.  What I think happened is many of these early migrating fish got caught up in Big Eddy and couldn’t find a way out until flows dropped.  What we have seen over the years is that at certain flows (40,000 cfs plus or minus) Chinook Salmon will stack up in this area.  At these flows, I think the unusual back eddies that form combined with high currents in certain areas confuse the salmon on how to navigate through it.  I suspect a few of these salmon were sitting in Big Eddy for almost a month.  If you were wondering, in most years we don’t allow salmon fishing in this area. 

 

That is all I have for you today.  I hope you all have a good weekend.