Sunday, August 12, 2012

Thermal block stalls steelhead

(NOTE: We will put a periodic update here at the top of this article.  The thermal blocking article was first posted August 9th.   The original article appears intact below the dashed line at the end of this update and graphics.)
 

--------------Update Posted @ 9:45 am, August 14, 2012-------------
Steelhead numbers crossing Ice Harbor Dam on Monday really tanked. With this heat wave we've been having, it's not looking real good for the thermal block to go away soon.  The NWS predicts a slight cooling this week but then a reheat afterwards.  We all know the hot temps will break down but every day the heat goes on is another day very few steelhead are heading up the Snake River system.  Here's a clip of the Columbia DART graph:



--------------Update Posted @ 8 am, August 13, 2012--------------
Well, folks, the info we posted below was an anomaly--a blip, if you will.  Steelhead numbers at Ice Harbor have dropped off sharply from that slight increase a few days ago.  NcNary number continue strong but Ice Harbor?  Forget it.  We will keep watching but there's nothing to get excited about right now.
--------------Update Posted @ 4 pm, August 11, 2012--------------
In just the last couple of days, steelhead passage at Ice Harbor has picked up.  It's not running anywhere near the 10-year-average but it's better than it was four days ago when Ice Harbor passage was roughly 90% less than McNary.  Now Ice Harbor is only about 78% less than McNary's three-day average.  That's a small change but could be a tip off that the water temperature of Lake Wallula behind McNary Dam may be warming to match the Snake River tailwater temp below Ice Harbor.  Unfortunately, we can't get good Lake Wallula temp data.  Below are two screen shots of the DART data base.  The top is McNary and the bottom is Ice Harbor.  The data is for August 3rd through August 10th.  Note that McNary's numbers for wild steelhead are actually slightly above that site's 10-year-average.

----------------Begin Original August 9th article---------------

A thermal block between the Columbia and Snake Rivers has slowed the summer steelhead run to a crawl.  The steelhead numbers logged at Ice Harbor Dam (the first of the series of Snake River dams) are roughly 90% less than McNary Dam near Umatilla, Oregon.

"The Lewiston Tribune" outdoor writer Eric Barker penned a great article August 5th describing the situation.  He relied heavily on insights from IDFG's Alan Byrne, Boise.  We talked to both Byrne and Barker today. Byrne confirmed the numbers on Barker's article.  Barker, in turn, agree to give us permission to reprint his article here.  (Thanks, Alan & Eric!)

Eric's entire article entitled "Warm water stalls Snake steelhead" appears below in italics.  Following the excellent article, we have included some graphics to help you begin to understand the situation.
----------------Begin Eric Barker article-------------------
Warm water temperatures in the lower Snake River have put the brakes on the summer steelhead run.

“The fish aren’t entering the Snake River,” said Alan Byrne, a fisheries biologist for the Idaho Department of Fish and Game at Boise. “It seems like we have a thermal block.”

It is not uncommon for the run to stall when there is more than a few degrees of difference in water temperatures in the Snake and Columbia rivers. Water in the Columbia near McNary Dam has fluctuated between 65 and 66 degrees since July 20. During the same time frame, water near Ice Harbor Dam on the Snake River has been 70 degrees or slightly higher.

Byrne noted that for nearly two weeks, fewer than 100 steelhead per day have been counted in the fish ladder at Ice Harbor. At McNary, the daily counts have been between 700 and 1,900.

“We have seen this before. We have a hot year, the Snake River gets pretty hot and the steelhead just are not coming in because the Columbia is cooler,” Byrne said. “We think what is happening is the fish bound for Idaho are just waiting for the Snake River to cool down.”

He still expects fishing to be good.

A group of salmon and steelhead managers in the Columbia Basin is predicting 311,800 A-run steelhead and 52,800 B-run steelhead will return at least as far as Bonneville Dam. Last year, 318,000 of the smaller A-run steelhead and 37,000 of the large B-run steelhead were counted at Bonneville. So anglers can expect slightly fewer A-run fish and more of the coveted B-run.

Byrne said about 50 percent of A-run fish, or 156,000, predicted to pass Bonneville should make it past Lower Granite Dam, and 70 percent of the B-run steelhead, or 37,000, should return at least as far as Granite.

That totals about 194,000 steelhead at Granite.

A short section of the lower Clearwater River from its mouth to Memorial Bridge at Lewiston opened to catch-and-keep fishing Wednesday. The rest of the river has been open to catch-and-release fishing since July 1.

The Snake River opens to catch-and-keep fishing Sept. 1.

Through Tuesday, 1,310 steelhead had been counted passing Lower Granite Dam since June 1. The 10-year average is 3,827.  

(NOTE: Article is copyright 2012 by The Lewiston Tribune and may not be used in any way without permission from the author or the newspaper.)
----------------------------End of Eric Barker article--------------------------------
First we have a couple of Google Earth screen shots.  One shows the location of McNary Dam in relationship to Ice Harbor Dam.  The actual confluence of the Snake River with the Columbia River is under the waters of Lake Wallula, the reservoir behind McNary Dam.  Red letter "A" is McNary; "B" is the confluence of the Snake and "C" is Ice Harbor Dam. (Click on any graphic for a larger version.)
Below is a Google Earth screen shot showing the location of McNary Dam with relationship to the Columbia's entrance into the Pacific Ocean. The red "X" marks McNary Dam.
The last seven days of steelhead passage through four dams is shown below in this order: Bonneville, McNary, Ice Harbor, Lower Granite.  (The numbers are current through August 8th for all four dams.) As you can see, there are four-digit numbers through Bonneville and McNary and only a trickle through Ice Harbor and Lower Granite. Temperature graphics are below fish passage graphics. Click on any graphic for a larger version.




Finally, we have the most current water temperature data for McNary and Ice Harbor.  Note that a week ago McNary (top graphic) was 66.7 degrees F and has risen to 69 degrees since.  Ice Harbor (lower graphic) shows a water temperature 1-2 degrees F higher than McNary's.  IDFG's Alan Byrne speculates the lower temperature of the Columbia may be due to a larger snowpack in the British Columbia portion of the giant river's headwaters.  On the other hand, the Snake River portion of this confluence could be due to the region's recent period of above normal temperatures. (NOTE: The data below only lists the tailwater temps for McNary while Ice Harbor has both Forebay and Tailwater.)  See summary comments below graphics.

The Upper Salmon River's fall steelhead season generally begins around the Autumnal Equinox or roughly September 20-21.  IDFG's Alan Bryne cautions not to read too much into the thermal block.  He indicated the steelhead can make up for the delay and arrive right on time.  He said he would want to guess whether the thermal block might delay the typical arrival time for the steelhead.  Byrne also noted that shorter days will help change the thermal block. The IDFG Salmon Region's Brent Beller plans to release his first fall steelhead fishing report October 8th, about two weeks after the theoretical beginning of the fall steelhead season.

Lost in the shuffle of the thermal block news is the fact that steel head numbers are lagging far below their 10-year average number at this time.  One commentator on this article stated this afternoon, "Since I started steelheading back in the Spring of '96 (summer '95 steelhead run), there have only been 3-7 years (depending on which dam you look at) that have looked worse than this."  The data from Bonneville Dam shown above would seem to bear out this comment.

We will continue to report on the summer steelhead run; how fish passage evolves along the Snake River Dams and how the season unfolds on lower reaches of The Salmon River.  Thanks for reading this long article.  If there are aspects of the steelhead run you wish us to cover, please send along your comments and suggestions via our contact information given elsewhere on this website.  Many Cheers & Happy Fishing, jp

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