Whirling Disease

Whirling Disease


Whirling disease strikes Maryland trout

Maryland ranks right up there with such states as Illinois and Nebraska in terms of trout fishing, so it was something of a surprise to learn that whirling disease had been discovered there. Whirling disease was found in 80,000 trout that swam in the concrete jungle of two state-run hatcheries. The fish were intended for stocking in various lakes and ponds around the state for put-and-take fisheries, but were destroyed instead. In completely unrelated news, Baltimore restaurants were offering amazing specials on stuffed rainbow trout the following week.

Whitefish hit by whirling disease

Whitefish, the often maligned, mishandled and unappreciated cousin of trout, are suffering a population decline in watersheds across the West, and whirling disease is the likely culprit. Although little research has been conducted on this subject a study is underway that will examine it. Anecdotal evidence however, points to whirling disease as the likely cause of the collapse of whitefish populations.While some shortsighted anglers might welcome this news, they should first consider the implications: Whitefish are important forage for large, predatory trout, especially the endangered bull trout. If whitefish numbers decrease, it could have significant effects up the food chain.

Hofer hybrid trout

Now for some good news: Fisheries biologists in several states have begun programs to breed a whirling-disease-resistant rainbow trout. Whirling disease is European in origin and, appropriately enough, American fisheries biologists have drafted a strain of rainbow trout cultivated in Germany to help combat it. The Hofer rainbows, as they are called, have been bred in German hatchery ponds for more than 100 years. Whirling disease is endemic there and the strain developed a high tolerance to the parasitic illness through natural selection.

Scientists in Utah have begun crossing the Hofer strain with rainbows from Montana's Harrison Lake, another strain with high natural tolerance to whirling disease, for stocking. In Colorado, biologists are into the second year of a program that stocks a cross of Hofer trout with Colorado River rainbows. Biologists are optimistic that the fish will successfully spawn within a year and that the offspring will inherit the same resistance to whirling disease.

For more information, visit whirlingdisease.montana.edu, whirling-disease.org