The Yellowstone River Killers

A killer was on the loose near one of my favorite stretches of the Yellowstone River. Its name is Ursus arctos horribilis. Every time I venture into the back country in Yellowstone National Park to fly fish the ‘Stone (below), I ready my hand to swipe the trigger guard off the bear spray holstered at my side. I’ve even practiced aiming from the hip; I might not have time to pull the canister from its holster if faced with a charging grizzly.

Recently, however, there was another killer on the loose in the Yellowstone River. It too has a Latin name.

But you won’t see it lumbering alongside the river. Even if you’re a few feet or a few inches away, you still won’t see it. The name of this killer is Tetracalsula bryosalmonae. It is a microscopic parasite that causes kidney disease in fish. Within a week, it recently wiped out 4000 fish (whitefish and trout). Apparently, it poses no health threat to other animals or to human beings.

The situation was so serious that the Montana Department of Fish, Wildlife, and Parks (FWP) closed a 183-mile stretch of the ‘Stone from the northern border of Yellowstone National Park near Gardiner, Montana, to the city of Laurel, Montana.

Parasite with a Vengeance

First discovered in Europe, the parasite was detected in some Idaho fish hatcheries as early as 1980. But it wasn’t until 2012 that the parasite was found in the Upper Snake River. Now it has attacked fish in the Yellowstone River with a vengeance.

Fisheries experts do not know if the parasite transferred via a human being or an animal. FWP biologists will study the situation and determine a strategy for managing and containing the parasite. Damage control is a more likely outcome than is eradication.

In the meantime, I am reminded of the importance of cleaning and drying our waders and boots before moving from one river to another. If you’re new to fly fishing, here are a few suggestions.

    Use a garden hose and vegetable brush to remove mud.

    Let the sun and heat dry out your waders.

    Don’t forget to turn up the gravel guards during the drying process to dry the underside of your waders.

    Use a blow dryer on felt soles and inside your wading boot.

Felt can hold moisture for a few days. Experts often recommend waiting between five to seven days before using a pair of boots with felt soles on another river. A few minutes with a blow dryer can, obviously, speed up the drying process.

Perhaps the move away from felt soles — which began five years ago but lost some steam – will emerge again. Maybe conscientious anglers will buy multiple pairs of boots, keeping a set for the Yellowstone, a set for the Madison, and so on. It’s too early to tell. Hopefully, biologists will figure out some strategies for anglers and other outdoor recreationists to avoid transporting the parasite.

Let’s do our best to pay attention to the problem and search for the best counter measures.

2 Replies to “The Yellowstone River Killers”

  1. I live in the Yellowstone drainage. With concerns over felt soled wading boots, I think I will reserve a set for the Yellowstone waters and use another for other waters to help minimize the possible spread for a couple of years. Isn’t the safety of our waters and fish worth the $100 for another set of felt soled boots?


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