Thoughts on the ocean, the environment, the universe and everything from nearly a mile high.

Panorama of The Grand Tetons From the top of Table Mountain, Wyoming © Alan Holyoak, 2011

Saturday, September 1, 2012

Fish kill on the Lower Teton River, Idaho - 2012

This short article appeared in the the Idaho Falls Post Register today (1 Sept 2012)



Whitefish die-offs puzzle fish experts
POCATELLO (AP) -- State fisheries biologists are reporting an increase in the number of mountain whitefish dying in eastern Idaho streams and rivers.
Idaho Fish and Game experts said the die-off is troubling and they are counting on the public to help figure out why.

The dead fish have turned up in recent weeks on the South Fork of the Snake River and the main stem of the Snake River. Reports of dead whitefish have also come from the Teton and North Fork of the Salmon rivers.

Regional Fisheries Manager Dan Garre said the cause is a mystery. He said it's interesting that the die-off is targeting whitefish typically under 10 inches -- and not trout.

Tissue samples have been sent to a state lab for analysis.

I read the article, and thought that was sad.  Interestingly I had some time today, and I headed to the lower reaches of the Teton River to do some fly fishing.  This part of the river, just north of the town of Teton, is usually a great destination and usually yields plenty of action, but not today.  I fished for nearly an hour with no luck at all.  I talked to other people also fishing the Teton today and they reported the same thing.

I know there can be slow days fishing, but for no one to have any luck at all is highly unusual.  What was also unusual were all the dead fish in the water along the river banks.  I also saw or heard only three times when fish surfaced.  That was over about a 3-4 hour period when I was fishing and walking the river looking at what I can only call a fish kill.

A fish kill is a situation where some combination of chemical, physical, and/or biological factors push fish beyond their tolerance ranges, killing many.  Well documented fish kills include situations where water temperatures spike or dissolved oxygen levels drop or chemicals are introduced to the water, or a disease hits a population, etc.  No one yet knows what is going on along the Teton, but this is what some spots along the north fork of the Teton River below the diversion dam, north of the town of Teton, Idaho.

There were dead fish all along the north fork of the Teton River between the diversion dam and the bridge of N 2400 E over the Teton River.  There were so many, in fact, that the smell of decaying fish was evident all along that reach of the river.  

That reach of the river is about 0.5 miles long, and I walked, counted, and photographed, all the dead fish I could see there.  Though this was an unscientific survey - just what I could see from the banks of the river - I saw about 100 dead fish.  All but one of these were mountain whitefish, but one was a cutthroat trout.  

The report that the fish kill was affecting only whitefish may have been preliminary, and it's possible that trout are also under environmental stress.  This photo, taken earlier today, shows a dead cutthroat trout near one of the banks of the Teton River - cause of death unknown.

The cause of death of these fishes has not yet been verified, but fish kills are known to have occurred in conjunction with low dissolved oxygen levels, high water temperature, and chemicals that have run off into a river or lake.  

One interesting piece of research (click the URL to see the entire article) on fishes in California reveals that whitefish are more susceptible to warmer water temperatures than trout.  Since this appears to be the case, whitefish may serve well as a "canary in a coal mine" (environmental indicator species) for trout streams and rivers.  I.e., when the whitefish are under stress, the trout may not be far behind.

I don't know what caused this fish kill.  All I know is that I've fished this part of the Teton River for years and I've never seen anything like it!  It's worrisome, and I hope the Idaho Fish and Game can figure out what is causing the fish to die.