.............................Fly Fishing Yellowstone National Park


I am calling this series Yellowstone Journals and Additional Information. It is a collection of a
rambling mixture of experiences on the streams with some notes, tips and additional
information thrown in. Some of this comes from my video tape logs (record of video shot)
and  notes made on my daily note books.

Firehole River - Part 4:

The Firehole River has changed over the years because of earthquakes. There
are a lot of smaller earthquakes in the area each year and that doesn't seem to
have much of an effect on the river. However, heavy earthquakes have changed
the amount of hot water entering the Firehole before, apparently opening new
places for the hot water to enter the stream. When this happens, the water
temperature increases, especially in the immediate area where the hot water
comes into the stream; but, It also has the effect of raising the overall
temperature from that point downstream.

Not long ago, there was a series of earthquakes in the area. I don't know and I
really don't know if anyone knows yet, if those earthquakes opened any new
areas that would add additional hot water. I certainly hope not. I don't think they
were strong enough but that is more hope than fact. As you probably know,
trout are cold blooded. Their body temperature is about the same temperature
as the water. Their metabolism is affected by their temperature. This affects the
amount of food they need to survive and of course, the amount they feed. The
amount of dissolved oxygen in the water is inversely proportional to the water
temperature. To put that in a simple way, hot water holds less oxygen than cold
water. The warm water can reduce the amount of oxygen necessary for the trout
to survive. When the water gets too warm for the trout, they move trying to find
cooler water. So, as the season gets underway and the weather changes from
cold to warm, the trout in many areas of the Firehole River move, seeking cooler

Iron Spring Creek and the Little Firehole River both contain water that is as
much as ten degrees cooler than the water in the river where they enter. Trout
will sometimes move up the smaller streams because of this. The extent they do
this is very dependent of the snow pack, the amount of rain and the weather.
They call them good water years and bad water years in Yellowstone country. It
has a heck of a lot to do with where the fish are and how much they feed.

A couple of years ago there was a fish kill in the Firehole due to the very hot
weather and the lack of snowpack and rain. This year the snowpack looks good
and hopefully the weather will not be abnormally hot. The last thing we need is
added doses of hot water from newly opened geysers or springs.

Tomorrow I will get into fish movement and seasonal changes on the Firehole.

Copyright 2009 James Marsh
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