New research on whirling disease, the malady killing
trout populations in the West, has scientists crossing their
fingers (HCN, 9/18/95: The West’s fisheries spin out of
control).
The disease targets fish less than nine
weeks old, destroying cartilage and causing the young fish to swim
in circles. In search of a remedy, Richard Vincent, a fisheries
biologist for the Montana Department of Fish, Wildlife and Parks,
coaxed three strains of hatchery rainbow trout to hatch in cool
water, where whirling disease spores cannot survive. By the time
the water warms enough to support whirling disease spores, he says,
the fish should be old enough to avoid contracting the disease.
Vincent theorizes that fish which hatch at cooler temperatures will
also spawn at cooler temperatures.
“If fish that
spawn at colder temperatures can pass that trait on – which is
unproven at this point – they will have a tremendous advantage,”
says Marshall Bloom, chairman of the Montana Whirling Disease Task
Force.
Bruce Farling of Montana Trout Unlimited
says Vincent’s water-temperature concept is promising but that more
research is needed.
“I really worry about people
thinking we’ve got the silver bullet because we don’t,” he says,
explaining that hatcheries often add to the problem by accidentally
releasing infected fish. Farling believes nature will eventually
outsmart whirling disease through evolution, as fish that can
resist the ailment survive while others die
off.
Evolution already favors native trout
species over the non-native rainbow. Native cutthroat naturally
spawn in stream tributaries that are too cold for whirling disease
spores. Bloom says in a laboratory setting, native trout are just
as susceptible as rainbow trout, but a different lifestyle helps
natives dodge the disease.
For information, call
the Whirling Disease Foundation (406/585-0860) or e-mail
whirling@mcn.net, or visit the foundation Web site at
www.whirling-disease.org.
This article appeared in the print edition of the magazine with the headline Cold can knock out whirling disease.
Republish our articles for free, online or in print, under a Creative Commons license.
