August 8, 2008 Into the weeds: Aquatic Macrophytes
Aquatic macrophytes in the Henrys Fork are submerged plants that grow out of the bottom of the river and are mostly submerged in the water. Some people call them weeds or moss; neither is an accurate term. They are not weeds in the sense of undesirable or noxious plants; rather they are highly beneficial and support numerous aquatic organisms. The term “moss” is typically applied to the macrophytes when they are uprooted and floating downstream in clumps, often then caught in irrigation canals, on hydroelectric intakes, etc.
The story of aquatic macrophytes in the Henrys Fork in the Caldera section of the watershed is far more involved than just the misnaming of these plants. Macrophytes are the primary components of instream habitat, because of the spring-dominated hydrology of the river. But the presence, species composition, growth, and height of these plants changes seasonally and annually, in relation to numerous factors. For a detailed synopsis of aquatic macrophytes of the Henrys Fork in the caldera then see: Interactions among aquatic vegetation, waterfowl, flows, and the fishery below Island Park Dam by Van Kirk and Martin (2000). For an in-depth look (pun intended) at how aquatic macrophytes affect water levels and flow patterns, then see: Aquatic macrophytes and instream flow characteristics of a Rocky Mountain river by Vinson et al. (1992).
Full article published in the Island Park News
August 1, 2008
Fish passage on the Buffalo River and what it means to the Henrys Fork is the topic of “This Week in the Caldera”. My article in the Island Park News (8/1/2008) describes the fish passage improvements made at the Buffalo River Hydroelectric Project and how they are intended to increase the number of rainbow trout in the Henrys Fork.
For more information on the fish passage improvements, see the article “ Fish no longer saying “Dam”!” by Lee Mabey, Henrys Fork fish biologist for the Caribou-Targhee National Forest. Lee spent many years working through the relicensing process of the hydroelectric project to make the passage improvements possible. For an in-depth review of things done to improve juvenile rainbow trout survival, see Jim Gregory’s article “ Winter fisheries research and habitat improvements on the Henry’s Fork of the Snake River” (2000).
Full article published in the Island Park News
July 25, 2008
Surviving during the winter downstream of Island Park Dam for a young-of-the-year juvenile rainbow trout means finding some habitat that will support you. For most that make it through the winter this habitat is found in the Box Canyon. For some juvenile rainbow trout - it might be in the Buffalo River - potentially taking advantage of improved fish passage to get upstream of the hydroelectric project dam. For other small rainbow trout, it may mean seeking refuge in one of the small tributaries that come into the caldera: Blue Springs, Antelope Park, Big Bend, Thurman, or Fish creeks. However, unlike the well-studied Henrys Fork (see Mitro and Zale, Seasonal Survival, Movement, and Habitat Use of Age-0 Rainbow Trout in the Henrys Fork of the Snake River, Idaho. Transaction of the American Fisheries Society 131:271-286, 2002. ) or the ongoing study on the Buffalo River, juvenile rainbow trout habitat or use has not been evaluated on the small tributaries. A study design to do just that is currently being developed by the Henry’s Fork Foundation.
Full article published in the Island Park News
Sediment in the Henrys Fork
Sediment below Island Park Dam has been discussed as a major contributor to the decline in the fishery from the early glory days to those of today. This is a complex discussion – one that deserves careful consideration.
Island Park traps sediment as water flows into it and slows. When the reservoir is drawn down to low levels, sediment is released and moves downstream. This scenario was played out in 1992 when the reservoir was reduced to a pool of 270 acre feet and an estimated 50,000 tons or more was flushed into the Box Canyon section of the Henry’s Fork. This event seemed a catalyst to the question of what happened to the fishery in the Caldera.
Many studies have been conducted to determine the effects of sediment transport in the Caldera, unfortunately, these studies lack the larger context necessary to really understand how sediment is transported. Sediment is naturally-occurring and without human interference such as grazing, and or such occurrences as the release of sediment built up behind a dam, is an ecologically important part of an ecosystem.
The Foundation has spent the last few years designing and implementing a stream channel restoration project on the Henry’s Lake Outlet. The Outlet feeds into Island Park Reservoir and has been a considerable contributor of sediment because of the dynamics of straightening the historic river channel. The Foundation is now in the phase of monitoring this project and will continue to work on projects like this to reduce sediment loads to Island Park Reservoir.
Full article published in the Island Park News
July 11, 2008
Winter flows are critical to a sustainable wild trout population. Research suggests that low flow releases from Island Park Dam during the winter months has an unfavorable effect on survival of young rainbow trout. These young-of-the-year trout need adequate habitat and often use the area along the edges of the river for cover during their early stages of life. When flows are low, the fish are forced to use the main channel; less habitat means fewer fish.
Island Park Reservoir is managed for irrigation needs and winter is the time when water is being stored for the coming year’s demand. Because of this scenario, water released during winter months is minimal and during the early history of dam management was at or near zero. A few years ago, the Henrys’ Fork Foundation and Trout Unlimited urged the government to include language in the transfer of title of Island Park Dam to Fremont-Madison Irrigation District that would set in motion a drought management process. The drought management process allows both irrigation interests and conservation interests to discuss amount and timing of water releases to better suit both needs. Because Idaho Water Law still dictates delivery of water and managers must carefully consider those water rights, there is no guarantee of winter releases from the dam but this process has proved beneficial even in the recent drought cycle.
Research, cooperation, and understanding have had an impact on a significant stretch of the Henry’s Fork River and its rainbow trout fishery. There is still much work to do and much more information to gather and the Foundation is hard at work and up to the challenge.
July 4, 2008
The Henry’s Fork Foundation News article in the Island Park News this past Friday described the methods and locations that the Idaho Department of Fish and Game uses to collect information on the rainbow trout population in the Caldera. Despite these fish numbers being referred to as “population estimates”, there is only one population of rainbow trout in the Caldera, i.e., these fish move throughout the Caldera to reproduce with one another. This may seem very self evident, but I sometimes hear people refer to the “rainbow trout population” on the Ranch. In actuality, they are describing the distribution of the population of rainbow trout on the Ranch.
Population estimates are collected by IDFG to monitor trout and whitefish numbers and population structure throughout the Henrys Fork. For more information and context for these fish numbers, including those in the Box Canyon, then please see, “What do the numbers mean?” by Steve Trafton (2003). A thorough coverage of the history of fisheries management in the upper Henrys Fork, including rainbow trout numbers in the Caldera, is covered by Van Kirk and Gamblin. History of Fisheries Management in the Upper Henry's Fork Watershed. Int. J. Sci 6:263-2284.
Full article published in the Island Park News
Welcome to the Henry’s Fork Foundation’s Caldera Project.
Starting in the summer of 2008, we have made the Ranch – the section of the Henry’s Fork flowing through Harriman State Park – and its surrounding waters the focus of an intensive effort to assess what we know, what we do not know, and what we need to do to preserve and enhance a fishery that is one of the touchstones of American fly fishing.
The impetus behind the project is simple: Fishing on the Ranch is not, by many accounts, what it used to be. Further investigation reveals that many things have changed, or are thought to have changes, over the past few decades: water flows, insect hatches, aquatic and riparian vegetation, and fish passage at dams, to name the more prominent examples. In fact, the history and ecology of the Ranch are a complex mixture of natural and manmade factors and influences, and figuring out what has happened, and what should be done, will be challenging.
The project in 2008 has three primary components: a review of the existing scientific literature and documentation that has been completed in the Caldera (defined here as the 28 mile section of the Henry’s Fork from Island Park Dam to Mesa Falls), the construction of an outmigrant trap on the Buffalo River to begin to assess the contribution that the Buffalo makes to the wild trout fishery of the Henry’s Fork, and a summer-long angler success and attitude survey to gain a better understanding of the Ranch angling experience. This website is your link to the project.
Please take a look at the information currently available on the site, and stay tuned: there will be several updates each week from the field, interviews, photos, and discussions of research and fisheries management questions specific to the Caldera section of the Henry’s Fork. Join us as we explore this extraordinary wild trout fishery.
Thornberry, Rob, "What's Wrong at Harriman", Post Register 19 Oct, 2008.
Full article published in the Island Park News
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