Rainbow trout have made a comeback in Montana’s Madison River, a world-class fishing site, after “whirling disease” nearly wiped them out 15 years ago.
The disease, caused by a parasite, slashed the trout population by 90 percent compared with levels in the 1960s and 1970s, according to the Associated Press. The recovery appears to be the result, in part, of the fish acquiring disease-resistant genes, possibly through the migration of trout from another creek.
