By Jeff Dean

As I’m sure many of you who have been fishing in the Gunnison Gorge and downstream of Pleasure Park have noticed, there are more than a few trout, particularly browns, which exhibit what appears to be a fungal infection.

Not sure of what I was seeing, or what was causing it, I did a bit of internet research. While what I learned may not be news to everyone, it was news to me, and I hope it provides an answer for anyone else who is curious about what is happening to the fish.

The (typically lethargic) fish I have been seeing with splotches of a cotton-like growth on their skin, are likely afflicted with a common fungal infection called saprolegnia.

Saprolegnia occurs naturally in aquatic systems. It occurs in fish hatcheries, as well as in the wild. And while it can be effectively treated in the “controlled” environment of a hatchery, treatment in a river or stream is a virtual impossibility.

Brown trout can become more susceptible to saprolegnia in the fall (and rainbows in the spring), when under stress due to long migrations in search of suitable spawning areas, and other activities associated with spawning. Additionally, unusually warm water temperatures, not uncommon in the fall of the year, as well as overcrowding and “fish fights” that can occur as fish congregate in the best spawning areas, can contribute to the stress on the fish. Not to mention the stress of being caught and/or mishandled by fisherfolk.

And while some trout will not survive the infection, it is not a “death sentence” for the fishery. The incidence of infection, and associated fish mortality, will ebb and flow, just as the incidence and intensity of the multiple factors that play into fish susceptibility will vary from year to year. So while, in my experience at least, it seems there are more infected fish in the Gunnison River this year, than in the previous seven I’ve been fishing it, it is not, necessarily, a harbinger of a dire future.

Jeff Dean is the president for the Gunnison Gorge Anglers.

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