Aquatic nuisance species are one of the most significant, rapidly-growing threats to aquatic ecosystems throughout the country, including Colorado.  As these species spread into new waters, they can displace the existing species and disrupt aquatic ecosystems and food chains.  Visit the Stop Aquatic Hitchhikers website to learn more about what you can do to avoid spreading these invasive species.

Some aquatic nuisance species that are of particular importance in Colorado are:

New Zealand Mud Snails

This pest is infesting 11 Western States now.  In late 2004, a population of the snail was found in Boulder Creek, in Boulder - the first confirmed finding of the snail in Colorado.  In April 2005, it was announced that mudsnails were also found in Elevenmile Canyon on the South Platte River.

What might this mean for Colorado's fisheries?  Dr. John Nickum (aka "The Old Professor") offered a scientific prospective in the spring 2005 issue of High Country Angler (click here).

Given the potential threat to fisheries, anglers should do their part to avoid spreading mudsnails on their gear.  Click here to visit West Denver TU's excellent website and learn more about the mudsnails and what you can do to avoid spreading them.

Whirling Disease

Whirling disease has devastated rainbow trout populations in some of Colorado's great trout rivers, including the Colorado, Gunnison, and South Platte.  While rainbows and cutthroat trout are highly susceptible, brown trout are quite resistant to the disease.  The whirling disease parasite attacks the cartilage of susceptible fish, causing a range of effects including blackening of the tail in young fish, skeletal deformities, "whirling" or tail-chasing behavior when fish are alarmed, and mortality.  Because their cartilage has not yet been converted to bone, younger fish are most vulnerable - and in rivers like the Colorado, whirling disease has virtually eliminated survival of young rainbow trout into adulthood.

CTU was in the forefront of efforts to work with the Colorado Wildlife Commission to reform stocking policies and end the stocking of fish infected with whirling disease into trout waters.  TU also published a "state of the science" overview paper to educate managers and the general public about this threat.  With partners like the Whirling Disease Foundation and with federal funding support through the Whirling Disease Initiative of the National Partnership for the Management of Wild and Native Coldwater Fisheries, we have also supported researchers nationwide who are helping build our understanding of whirling disease and how to combat it.

Didymo

Didymo (the algae Didymosphenia germinate), also known as "rock snot", is believed to be a native algae to Colorado but was a rare occurance in mountain lakes. In 1975 it was first noticed in the Frying Pan River. In the last 10 years, for reasons unknown, it has been expanding its range rapidly in Colorado and other places.

The single cell diatom, one of the most primitive forms of life, when dead floating down a stream or hanging from branches looks like wet whitish or dirty brown tissue paper. Growing in a river bottom it looks like a thick moss carpet covering rocks. It feels like stringy rough edged slime. Didymo can expand into long continuous sheets reaching from bank to bank and extending for miles. The algae isn't known to harm trout directly but there is evidence it interrupts the life cycle of crustaceans which the fish feed on. Didymo also out competes other algea that the crustaceans primarily feeds on.

The "Old Professor" shared some perspectives on Didymo in High Country Angler.  The U.S. Environmental Protection Agency also has an informative website about this potential threat.