My fishing during calendar year 2015 ended the same way it began: the sun had just dropped below the horizon, ice was beginning to form on my line, and in the last purple light of a short winter evening I could see a pod of trout in front of me, rising to midges.
Photo: Early winter evening on lower Henry's Fork, December 2015.
I recently created two figures to accompany the quick reference poster of water quality on the Henry’s Fork that was featured in our blog post on October 30th. These figures illustrate the optimal, sub-optimal, stressful, and lethal temperature ranges for Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss).
During the Thanksgiving Holiday, we received a number of calls from concerned anglers about low flows and ice formation on the Henry’s Fork downstream of Island Park Dam. There is no question about it—flows are low; that’s not unexpected following the driest water year since 1941 (see previous blogs and newsletters for details). However, flows are higher than expected given how dry it is, and temperatures have actually been fairly mild compared to other winters when flows were low.
But, your questions and concerns motivated us to dig into the scientific literature and data and provide information on relationships among winter flow, temperature, and trout survival on the Henry’s Fork. We spent most of this week putting together some information we hope will help answer questions and ease fears about the combined effects of low flows and cold temperatures on trout survival in the Henry’s Fork.
Each summer the Henry's Fork Foundation puts up 3 miles of fencing, 1.5 miles of fence across from Pinehaven at Wood Road 16 and 1.5 miles of fence at Last Chance, to protect the banks of the Henry's Fork from potential degradation and erosion by cattle. Then, once the cattle are moved out of those sections for the season in late fall, we take the fencing back down in preparation for winter.
I hope you have been taking lots of photos this year as you lived, worked, or played within the Henry's Fork watershed, because the Foundation is sponsoring a photo contest. Photos must have been taken within the watershed during calendar year 2015. So you still have time to get out and snap a few more photos. Winter is coming, and snow pictures are great.
To support our water quality monitoring efforts, we have a new quick reference poster in the office! For now, the poster displays the recent, daily range of dissolved oxygen (averaged over the previous 4 days) and the weekly average temperature from our sampling/sonde sites. We have seven sites that we capture data from; I download data from 3 of the sondes one week, then retrieve data from the remaining 4 sondes the following week. Therefore half of the displayed data are from the previous week, and the other half of the site data are two weeks old.
A few months ago I was contacted by Michael Downey, a water resources planner in Montana's Department of Natural Resources Conservation (DNRC). He had read about a study I directed a few years ago that investigated the effects of development on hydrology and water management in the Henry's Fork watershed and invited me to come talk about this study--and more generally about groundwater management in Idaho--at a day-long technical workshop in Helena. I just returned from that workshop and thought it relevant to share both my presentation and a few interesting observations with you.
On October 7th, HFF worked with partners from Fall River Rural Electric and the U.S. Forest Service to remove the outmigrant trap that was part of our Buffalo River project. The decision to remove the trap was made jointly by HFF, Fall River Rural Electric, U.S. Forest Service, and Idaho Department of Fish and Game, after reviewing data collected at the downstream trap since 2009. Through the trap’s operation, we have learned that many thousands of young rainbow trout migrate downstream out of the Buffalo River each spring.