• Visit: Moldy Chum
  • Visit: The Horse's Mouth
  • Visit: Chi Wulff
  • Visit: Parks' Fly Shop
  • Visit: Montana Cowgirl
  • Wednesday, April 11, 2007


    Colorado Follows Utah In Seeking Resistant Trout
    is whirling disease on the run?

    The whirling disease parasite, Myxobolus cerebralis, digests and destroys cartilage in the cranial region of infected fish. (Courtesy Montana University Water Center)

    .. A recent post in the Trout Underground notes that Colorado is using the techniques pioneered by the Whirling Disease Foundation to breed a disease resistant trout. This effort is similar to the one Utah developed to aid their stocking program. Two strains of Rainbow Trout are used by Utah: the Harrison - a slow-growing semi-resistant variety, and the Hofer strain of trout. This is similar to the program in Colorado.
    .. The Hofer rainbow strain has spent some time as an introduced species in Germany, and apparently had, during that time, developed a significant resistance to whirling disease. The eggs from the Hofer strain came to Utah from Colorado in 2004.
    .. The resulting Rainbow has been nicknamed the HO-HA TROUT. We noted the results of this research in January. There is now a study period in Utah to see if the fish are as catchable and popular with fishers as the previous strains of Rainbows - some indigenous and some introduced.
    .. One significant aspect of the Utah effort is the reliance on wild stocks of fish in the breeding program. These combined with the Hofer stocks, (which are a docile fish bred for generations as a 'food' trout,) may or may not produce a 'sport' fish. The same concerns are being noted in the Colorado project.
    .. The Whirling Disease Foundation has been instrumental in these studies. The foundation has also noted that the reduced populations of Rocky Mountain Whitefish led to the understanding of the disease vector.
    .. Tubifex worms are an intermediate host of the disease and research is being conducted to find resistant strains of these mud loving critters as well.
    .. The diminished populations of Whitefish give concern because they are a valuable forage fish for trout and char - including the Bull Trout. The Whirling Disease Foundation has completed a pilot research program aimed at exploring this aspect of the disease and its impact. Some of us enjoy fishing for Whitefish, others demean both the fish and the sport. The species itself, however, is crucial in the understanding and combating whirling disease.
    .. Several research projects are currently underway that are sponsored by the Whirling Disease Foundation. The three phase research is just now beginning to show some results. The Utah and Colorado fish breeding programs are one of the initial outcomes of these projects. This is an effort that is over a decade old and is ongoing. It has involved universities, agencies, groups, clubs, and individuals across the nation and around the world.
    .. Understanding of the disease and more importantly the impact of hybridization is crucial to maintaining an healthy sport fishery, and an ecologically sensitive program. As noted by Hedrick & May, et al:
    Resistance to a single disease is only one of many criteria that need to be considered when moving plants and animals from one geographic region to another. If broader ecological implications of movements are not considered, greater harm than good may result. Thus, the second phase of experimentation provides assurances that the HR trout, having developed resistance to whirling disease, have not become extremely susceptible to other microbial pathogens they may encounter. In addition, these trout will be thoroughly examined to determine if pathogens unknown in North American trout are potentially transmitted with them via eggs. Such studies are critical before further discussions on the potential applications of these fish in North America can proceed.
    .. Protect Your Waters has an informative section on their web site about the disease and what we should know, and what we should do. Results are promising, but not definitive; a battle has been won, but the war will continue for quite some time.

    .. A 'sidebar story' is in the offing for Yellowstone National Park. Since most of the Rainbow Trout in the Park are introduced species, will Yellowstone follow this lead? And, in light of the recent court decision that opts for morphology over genetics, will the fishers of Yellowstone pretend that . . . " if it looks like a cutt . . . . ."