Northwest regional anglers have long held the highest regard for the South Fork Boise River’s blue ribbon trout fishery. Revered primarily for its hard-fighting, selective redband rainbows, local fly fishers often speak in hushed tones in “water cooler” conversations lest they reveal information that might draw more anglers to its already crowded banks.
Despite historic top quality fishing a mere 75 miles from Boise, recent electro-fishing surveys by the Idaho Department of Fish and Game have confirmed anecdotal angler concerns that the South Fork (SFB) fishery appears in decline. Specifically, the Fish and 
Game’s bi-annual electro-fishing results (2005, 2007) have clearly demonstrated a noticeable decline of both total redband numbers and several substantially depressed age classes. Yet the same survey points to a disproportionately high number of larger (> 400mm) fish within the population sample.
For southwest Idaho’s top fishery these confounding results causes much chin-stroking and contemplation among the angler enthusiasts. “Are these larger redbands a result of the mormon cricket invasion of the South Fork Canyon earlier this decade?” asks TU member Andy Brunelle. “Certainly the pulse of protein when the crickets covered the stream could have contributed to these unprecedented numbers of really large fish.”
If the South Fork’s redbands are in trouble, what does this, likewise, portend for its local bull trout and mountain whitefish populations? Ted Trueblood chapter members have been scratching their heads since IDFG staff presented their latest electro-fishing numbers at a Chapter meeting last May.
Through the summer TU members as well as colleagues from the Boise Valley Fly Fishermen wondered whether the tailwater fishery suffered from a lack of spawning sized gravel due to Anderson Ranch Dam. Perhaps a gravel augmentation project like that completed in Boise in 2005 would be necessary.
TU and BVFF subsequently requested a meeting with the agencies to discuss potential habitat improvement projects in the SFB such as spawning gravel augmentation. Along with IDFG, the Boise National Forest and the Bureau of Reclamation came for an afternoon of presentations and discussion. “With help from the agency professionals the group reached consensus there would be little value in immediately pursuing habitat improvement projects prior to understanding potential source populations for the target fishery in the South Fork,” said Brunelle. “Instead, we learned how gathering genetic information on redband trout would provide a foundation by which a conservation strategy for the South Fork fishery could be developed.”
Following the general meeting Brunelle joined with Trueblood board members Richard Prange and Chris Jones, TU staff biologist Dr. Helen Neville, and Boise National Forest fisheries biologist Mike Kellett to hatch a plan was to pursue Embrace-A-Stream grant money for a genetic study of SFB redbands.
“If we get the funding sampling will commence in 2008, under the direction of IDFG and USFS electro-fishing crews, and finish in 2009 with genetic analysis results to immediately follow,” said Jones. An attractive sampling method of hook and line (fly fishing) by TU and other clubs’ volunteers (Wooly Buggers, Magic Valley Fly Fishers, etc.) will assist biologists in collecting a large, representative sample for analysis. “You can bet I’ll be there with my sampling equipment and lab coat,” said Jones.
Genetic diversity and genetic population structure have become important tools for the recovery and management of wild fish (and other species). Genetic data is used to make inferences regarding extinction risks, migration routes and effective population sizes. “This type of analysis has been identified as an essential component for the development of management and conservation strategies for wild trout,” said Brunelle.
Genetic research of SFB redbands likewise fits hand and glove with current Boise River basin efforts of TU staff biologist Helen Neville. “Dr. Neville has sampled and analyzed over fifty populations of redbands across the drainage,” said Prange. “If, as we suspect, the SFB redbands spend part of their life history in other rivers such as the North and Middle Fork Boise Rivers, then we gain more information toward redband recovery. The value of this information cannot be over stated.”
Issues affecting connectivity, water quality, spawning and rearing habitats are all paramount to SFB redband population survival. Key components of redband life history and ecology will be better understood through genetic research. Then, and only then, can we help biologist address missing or limiting components of our precious fishery.
ITU Vice President Chris Jones points out that our EAS-funded study may reveal that a significant portion of SFB redbands migrate from the Middle Fork and North Fork Boise River drainages. “If so, there could be ramifications this information would have on the proposed Atlanta Gold Mine, the long dormant but never dead Twin Springs Dam proposal, as well as protection of Forest Service roadless lands across the headwaters of the Boise River watersheds.”
