Plague. Pestilence. Epidemic. And all that was before the snakehead arrived.
Pity the plight of the poor aquatic biologist trying to maintain nature’s balance in a brave new world of angler mobility and creepy-crawly stuff nobody knew existed a few years ago.
Taken together, various diseases and successive waves of non-native critters are costing wildlife departments and the sportsmen who support them many millions of dollars and even more quality recreation hours.
Nowhere has the tab been greater and the targets harder to pinpoint than in Colorado. In the past decade, the Division of Wildlife spent more than $11 million to rid nearly every hatchery of whirling disease, an infection that kills young trout and essentially has wiped out natural rainbow trout reproduction.
With relief also in sight from genetic adaptation involving a resistant strain of rainbows, much of the heavy lifting with WD seems to have been accomplished. But these millions spent and more to come represents money that might have gone toward other beneficial projects, such as expanding angler access.
Just when it seemed the agency finally is winning that battle, along comes the New Zealand mud snail and the threat of a lot of other malefactors you might not even want to think about – particularly just before you fall asleep.
Take the northern snakehead, for example. You might have seen some news clips of this nasty-looking Chinese import, which in recent years gained a foothold in the Chesapeake Bay area. The snakehead has the ability to live for days out of water and, while it lacks the outright mobility of another interloper, the walking catfish, it potentially can wallow its way from one body of water to another. Mostly, it’s a top-end predator capable of taking a serious bite out of sportfish populations.
What’s worse, it also can withstand a wide range of temperature and environmental variations. Eric Hughes, Colorado’s aquatics chief, has little doubt this marauder could make a home in Colorado’s lakes and ponds, given benefit of a little traveling opportunity.
“These days fishermen are so affluent and mobile. There’s added opportunity to transmit a lot of diseases from one place to the next,” Hughes said.
Add to this the persistent transfer of exotics, such as the snakehead and various aquarium species plus the well-meaning, but equally damaging transplants by angling bucket brigades, and we have all the ingredients for a world of mischief.
In addition to the more visible transgressors, biologists deal constantly with the threat of microorganisms, such as the mysterious virus that caused the destruction of 3 million trout at Mount Shavano Hatchery in 1983. To guard against such maladies, DOW no longer transfers live fish among its hatcheries and has constructed quarantine and isolation facilities to protect native trout used in restoration efforts.
While whirling disease fades into the rearview mirror and snakeheads remain a blur over a far horizon, Hughes still has plenty to worry about inside the tiny shells of mud snails.
First found in late 2004 in Boulder Creek, this tiny pest subsequently was detected a year ago on the South Platte River in Elevenmile Canyon. The dual discovery prompted officials to launch an all-out information campaign designed to inhibit further spread.
Barely one-eighth-inch long and able to live out of water for a considerable period, the New Zealand import can be transported by boats and trailers as well as the usual assortment of fishing gear.
Boaters who visit infected waters are urged to clean their equipment at a car wash; anglers should soak and clean boots in a 50 percent solution of water and product 409 antibacterial kitchen cleaner. It should be noted that other 409 cleaners aren’t effective.
Thus far, biologists haven’t located other snail infestations.
“We’ve targeted heavily used stream segments and found no other infected spots,” Hughes said. “This doesn’t mean they’re not there, just that we haven’t found them.”
Mud snails generally aren’t noticed until there’s a population explosion, which might take two or three years.
“They’re so small that tens of thousands might go undetected,” Hughes said.
Mud snails feed on the same nutrients, primarily decomposed vegetation, as the invertebrates that sustain trout. An infestation might eliminate all available fish food in a section of river. There’s no scientific baseline on trout growth, Hughes said, but observation in other states indicate some reduction in biomass.
A quirk of the snail problem is the little buggers tend to eat themselves out of house and home, populations crashing as quickly as they bloom. Snails first appeared in Western rivers more than a decade ago; thus far, they have proved a nuisance rather than a devastation.
But you never know where the next epidemic is coming from, whether it’s zebra mussels or water fleas or any of a number of odd bacteria or viruses that spin from Hughes’ vocabulary.
It’s still safe to go into the water. Just be careful what you take with you.
Charlie Meyers can be reached at 303-820-1609 or cmeyers@denverpost.com.
