Yellowstone Trout Are Thriving

Yellowstone River, Paradise Valley, Montana

News Reports Terribly Misleading

BY DAVID S. LEWIS

09/09/16

News about the Yellowstone River recently has been bad, and terribly misleading, after Montana Fish, Wildlife and Parks closed an unusually long stretch to fishing and recreation on August 19. The Associated Press has led stories with phrasings leading readers to believe that trout in the river have been decimated and are dying off, but nothing can be further from the truth. The New York Times, a publication poorly acquainted with Montana, publicized the closure as well. But we find more sensationalism than explanatory details in these stories conveying relevant facts.

As is not uncommon, numerous whitefish were observed to have died on the Yellowstone, upriver from Livingston, Montana, north of Yellowstone Park, over a 25 mile stretch. This has occurred in the past, we are told by veterans of the river, and in fact is common, though the recent die off was greater than those on record, which put FWP temporarily in a state of confusion, at least until they could gather more data on the river. And so the closure of the river for so many miles, all the way to Laruel, Montana, was, in effect, precautionary, until the agency could learn what was going on. And while the undesirable white fish (to anglers) lost a few thousand of their total population (perhaps 4 percent), anglers and river enthusiasts might take heart that so far trout are not turning up dead in any serious way, indicating that they are strong and resilient in the Yellowstone River.

FWP informed us (we have had conversations and interactions) that a parasite has been found in the river in higher concentrations than usual, and in various species of fish, that leads to kidney failure or septic shock. Keep in mind that low water, and the Yellowstone has been running quite low this late summer (in other words, with less water) concentrates the parasite. Keep in mind, also, that these fish are more resilient in cold water, while this particular stretch of the river was warmer than usual this August (about 70 degrees Fahrenheit). But even so, only a tiny number of trout have been hit by the parasite in a meaningful way, and most that have tested positive were healthy, suggesting they are immune or otherwise not seriously affected by the parasite. These trout, what’s more, being exposed to the parasite, develop immunity if they have not already done so, leading to a potentially healthier fishery than before. And, one would think, the trout will fare better generally in terms of competition after a white fish die-off, though white fish will come back as well (presumably), as mother nature works her adaptive magic by endowing individuals with a natural resistance that happens quickly as each fish contacts the parasite and survives.

This parasite, by the way, is found in various intact Western and European fisheries, including in Idaho.

Also at cause, in terms of the whitefish die off,  has been a combination of conditions—low water and warm water due to a warm early spring, and probably a stretch of river with lower oxygen. The Superintendent of Yellowstone National Park, for instance, told us personally that zero fishkills had turned up in the Park, just south of the affected area, because in the Park the waters of the Yellowstone are higher, colder and deeper—conditions beneficial to fish and that dilute the concentration of the parasite (which by the way is not harmful to humans or animals). But still, in the worst hit area of the Yellowstone River, the trout are doing well, according to FWP, and a retired guide we know reported good fishing just north of Livingston (the river south of town being still close in early September for testing, but with the tributaries open).

FWP, having perhaps over reacted by closing so much of the river, though understandably, has now begun opening parts of the river to fishing and recreation, though a main stretch still remains closed as of the first week of September, as they test fish for the parasite.

The presumption is that as temperatures drop, the white fish (and various species of trout) will become more hardy, and as the river rises in the spring, the situation will be found to have dramatically improved. This process seems already to have begun with the recent colder day and nighttime temperatures.

Trout populations, though, all along, all species of trout, have been healthy and resilient.