Monday, January 7, 2008

South Fork Cutthroats Update

As many people know, the native Yellowstone Cutthroat trout in the South Fork of the Snake River below Palisades Dam are under siege from the Rainbow trout population in the river. The ‘bows spawn with the cutts and create hybrids (cuttbows) that are diluting the genetics of the native cutthroat and allowing the rainbows and the hybrids to potentially overtake the upper stretches of the river, which were once a haven for the native cutts.

A South Fork Cutthroat (photo © 2005 Arlen Thomason. Used by permission).

In an effort to save the Yellowstone cutts, Idaho Fish and Game (IDF&G) and TU have implemented various conservation projects, including the repair and restoration of important cutthroat spawning habitat, flows management from the dam that simulate the conditions found on the river before the dam was built, and catch and release of all cutthroat trout coupled with no limit (and encouraged harvest) of all rainbows and hybrids.

The most recent newsletter for the local chapter of Trout Unlimited (the Snake River Cutthroats) included a letter from Jim Fredericks of IDF&G updating the progress of these measures based on the data from last fall’s population estimates. Here is the majority of it:

I wanted to get an update out for folks on the population estimates in the South Fork based on our October electrofishing efforts. By and large, it was good news. We saw an overall increase in the cutthroat population and a big jump in our yearling estimate. Brown trout and rainbow trout were also up from last year. Combined, we're looking at some of the highest overall trout densities we've ever seen (about 4,500 fish/mile). That's the good news. The bad news is that we did see a pretty good yearling crop of rainbows. This isn't too surprising, given the fact that the spring flows in 2006 were not great. We are getting a much better idea of the timing and magnitude of flows that we need to make a difference in cutthroat and rainbow recruitment.

Along those lines, we just met with water users and BOR to discuss this years winter flows and how we can increase our chances at getting a good flow in May-June of '08. Given the level of Palisades Reservoir, the water users are very concerned about not having enough water high in the system and sending it down before the irrigation season. Their request was to try 700 cfs. We agreed that winter flows of 800 cfs would be acceptable if it increased the likelihood of a spring flow of 20,000 cfs in the critical time. As we've known all along, we can never get a "guarantee" of spring flows because of all the uncertainties in snowpack and spring rains, but we can increase the likelihood. I know this will be a concern with many folks. We''ve continually said that we do not want to go below 900 cfs until we can see how the population holds. I think we can now safely say that it has NOT been a detriment to the fishery, and in fact the overall population is about as high as we've ever seen it after three years of 900. I don't believe the risk associated with going to 800 outweigh the benefits of increasing the potential for good spring flows. Another factor that plays into the SF winter flows are the Henrys Fork winter flows. We will be pushing for an increase in those flows as soon as possible. By agreeing to reduce the SF by 100 cfs, we've gained support to increase the HF sooner than later. We KNOW that 100 cfs makes a big difference below Island Park.

As those of you who've been involved in these discussions know, it's very complex and there are a lot of different perspectives. All in all, I think that given the awful water year that we just finished and the low reservoir levels, we've done quite well on both the HF and the SF. One thing I'm certain of is that we're in a whole lot better shape than we'd have been in under similar circumstances 10-20 years ago.

I think there are many positives to be noted here. First, the trout populations on the South Fork are doing great (4,500 fish/mile). Second, the water users are working together, or at least trying to work together. And third, Fredericks and his staff are trying to do what’s best for both the Henry’s Forks and the South Fork. The flows coming out of Island Park Dam are crucial to developing and sustaining the populations in both the Box Canyon and the Railroad Ranch section of the Henry’s Fork. So, giving a little on the South Fork to get a little on the Henry’s Fork is very important.

Fredericks is doing a nice job for the fisherman in the Upper Snake River region (although I would love to see IDF&G implement a serious conservation program on the Teton River as well). One of the things I hope to incorporate into this site is an email Q&A with various members of the fishing community in the region, and Fredericks will be one of the people I attempt to strike up a conversation with.

No comments:

Post a Comment