It’s a simple question and one on the minds of many Madison River anglers, but as a recent discussion with Montana’s Whirling Disease Research Director Dick Vincent pointed out, it’s VERY difficult to answer. The answer is complex and a classic example of a “good news/bad news” scenario. First, even though the Madison River has been the poster child for severe whirling disease, the infection in the Madison is considered moderately high. On the MacConnell/Baldwin scale where 0 is undetectable, 5 is most severe and an infection about 2.5 causes some mortality, the Madison infection averages around 3.5. At this level, it is likely that the Madison will have its good years and its bad years. Even pre-whirling disease, the Madison had cyclical trout population peaks and valleys, and although whirling disease (WD) is now present in the Madison and has impacted rainbow trout populations, this cyclical nature is likely to continue. The bad news is that WD is still a significant problem in the upper Madison River above Ennis Lake. The good news is that rainbow trout populations in the Madison have rebounded significantly from the tragically low levels of the mid-90’s and brown trout populations today are almost exactly what they were pre-whirling disease. Also, as those who have fished the Madison recently know, the fishing has been respectable. The bad news is that this rebound does not appear to be grounded in any permanent, genetic resistance to WD, and unfortunately, the bounce back may not be permanent.

The Madison River is one of the most thoroughly studied trout streams in the world. Trout populations are counted annually and flow and temperature data, and trout life history information have been collected over several decades. There are lots of numbers to look at, and they can be difficult to interpret. The following comparison of trout productivity in a 3 mile study section in the upper Madison best illustrates what has happened in the river since the early ‘80’s.

Time Period   Total Pounds of Rainbow Trout       Total Pounds of Brown Trout

                        Per 3 Mile Study Section           Per 3 Mile Study Section

1982-1990(pre-WD)         5007                                               3905

1991-1998(WD impact)     1320                                               2871  1999-2003                      3259                                               3944

As you can see, WD, which likely was introduced in the late 80’s, had an enormous, initial impact on the rainbow trout population. The “rainbow biomass” dropped from an annual average of 5007 total pounds of rainbow trout in the 3 mile study section to a low of 1320 pounds during the heavy infections of the mid-90’s. Even browns, which are much more resistant to WD, appear to have suffered an initial hit during that same period. Today, the rainbow biomass has rebounded to an average of 3259 pounds, but this is still well below, nearly 35% lower, than the pre-WD levels. The brown trout biomass, on the other hand, is almost exactly what it was in the pre-WD time period.

So, what does this mean for upper Madison River rainbow trout? Unfortunately, the answers are not clear. Extensive research has produced several interesting findings. First, the rainbow population rebound appears to be influenced by environmental factors with flow levels being very critical. One important study found that higher than normal flow levels at the time of rainbow fry emergence appeared to dilute the whirling disease infection thereby increasing survival rates. These phenomena likely produced the sizeable rainbow trout year classes in 1998 and 1999. Unfortunately, there are some disturbing signs that the rainbow trout population may be headed for another downward trend. There is data that indicates rainbow trout growth rates are declining, and it appears that whirling disease infections experienced by young trout may produce lingering, debilitating effects that may cause problems later in their lives. These are disturbing and perplexing questions that obviously merit further study. Yet, there is hope. Research into whirling disease resistant rainbow trout may hold a key. This research is progressing and combined and with other management practices, the use of a whirling disease resistant rainbow trout may help turn the tide in the battle to restore Madison River rainbow trout populations to pre-WD levels. When will this happen? Scientific research with animals takes time, and it’s going to take a few years to get the answers. We must be patient.

What’s the bottom line for Madison River anglers? First, whirling disease hasn’t done anything to change the magnificent scenery. The upper Madison is still one of the most beautiful places on God’s green earth. Second, even with a depressed rainbow trout population, the browns are still there in pre-WD numbers and along with the remaining rainbows, we have very good fishing. Personally, I fish the upper Madison as much as I ever did, and I will continue to fish there. My expectations on catching rainbows of the size and in the numbers I caught back in the 80’s have changed, but this doesn’t diminish my enjoyment. Should we be satisfied with the current conditions? Should we accept them as the status quo? I think not and certainly Dick Vincent and Montana Fish, Wildlife, and Parks don’t think so either. As long as there appear to be possibilities to manage the disease and restore the Madison River rainbow populations to pre-WD levels, we’re obligated to keep the whirling disease research process moving forward. So, please enjoy the fishing treasure that is Montana’s Madison River, and please continue to support the work of the whirling disease research community and the Whirling Disease Foundation.