In December of 1994, Montana Fish, Wildlife and Parks announced that whirling disease had been discovered in Montana and was linked to a severe decline in the rainbow trout population in the Madison River .   At the time, little was known about whirling disease, but effective partnerships between the federal government, the states, and the private sector supported an impressive research effort that focused on filling in the knowledge gaps about the life cycle of the parasite, the alternate host Tubifex worm, and the susceptibility of the trout and salmonid host.   As scientists filled these knowledge gaps, the research focus shifted to applying the newfound knowledge to managing the disease.   At this time, while there is no “silver bullet” capable of eradicating the disease, there do appear to be several viable disease management options.  

 

In 2000, the Whirling Disease Foundation of Bozeman, Montana was approached by two leading whirling disease researchers with information that a strain of rainbow trout from North America that had been introduced into a family owned trout hatchery (Hofer) in Germany 150 years ago may possess a high degree of resistance to whirling disease.   Initial testing, supported by the Whirling Disease Foundation , proved that this rainbow possessed a high degree of resistance to the disease.   The next phase of the resistant trout research is now in progress, and includes work utilizing traditional techniques of crossing the resistant rainbow strain with other strains of susceptible North American rainbow trout with a goal to identify off-spring that possess the desired qualities of the North American rainbows i.e. sporting qualities, ability to spawn and survive in the wild, etc., with an increased resistance to whirling disease.   These fish could then be used to restore and replenish wild rainbow stocks that have been decimated by the disease.   Quite recently, research in Montana revealed that another strain of rainbow trout, the Desmet rainbow, may also possess a high degree of resistance.   The states of Montana and Utah have begun research into the resistance of the Desmet rainbow, and the Whirling Disease Foundation is working closely with all the states to coordinate and help resistant trout research plan.   

 

There are several other promising management options being studied.   In Colorado , a natural wetlands filtration system has proven effective at filtering and removing the fish infective form of the whirling disease parasite from a heavily infected tributary of the Frying Pan River.   Wetlands filtration could provide a natural method for managing the disease in low volume whirling disease infected tributaries.  

 

Research on Montana ’s Madison River demonstrated that raising river flows at the time of the emergence of rainbow trout fry from spawning gravels served to dilute the whirling disease infection thereby lowering the level of infection in the juvenile trout, and increasing year class survival rates.   Such flow manipulation could occur on dam controlled rivers and be a part of the management matrix.   

 

Research has demonstrated that populations of the alternate host Tubifex worm thrive in degraded stream habitats.   Channel rehabilitation and habitat restoration projects could prove help lower the level of whirling disease infection.     

 

Recently, there has not been a great deal of publicity regarding whirling disease.   Unfortunately, the lack media coverage doesn’t mean the disease has gone away.   In Montana ’s Missouri River , whirling disease infection is escalating in the Dearborn River , an important Missouri River rainbow spawning tributary.   Following two good year classes of rainbows in 1998 and 1999, the Madison River continues to have problems with whirling disease.   In addition, whirling disease infections are increasing in the Smith River , the Blackfoot, the lower Clark Fork , Rock Creek near Missoula , and in the East Gallatin near Bozeman .

 

Whirling disease is not just Montana ’s problem, either.   Colorado continues to experience severe infections in 5 of 6 major river drainages, and the state has spent millions of dollars on hatchery cleanup and protection.   In Wyoming , whirling disease has caused problems in the state’s hatchery system.   Utah continues to do battle, and whirling disease recently arrived in New Mexico and threatens native Gila and Apache native trout reintroduction programs.     Some of the most disturbing news comes from Yellowstone Park .   Yellowstone Lake cutthroat populations have been declining recently and this decline had been largely attributed to the predation by Lake Trout.   It has been discovered that several Yellowstone Lake tributaries suffer from whirling disease infections.   Pelican Creek, an important Yellowstone Lake spawning tributary, is so severely infected that scientists have found less than 10 juvenile Cutthroat from recent year classes, this from a stream where the spawning run once numbered over 10,000 trout. Things are not getting better, and there is still much work to do.   If you would like to support the work of the Whirling Disease Foundation , please contact the Whirling Disease Foundation , PO Box 327 , Bozeman , MT   59771-0327 , phone 406-585-0860, email whirling2@mcn.net or visit the Foundation’s website at www.whirling-disease.org