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


Freestone Streams - 3
After the stream reaches the valleys, it slows down and congregates in larger
pools with riffles. Since the water temperature is warmer than the water at
higher elevations and since the pH has become even more alkaline, plant
growth may be present. The stream's substrate usually consists of more soil and
less rocks and burrowing mayflies may exist. The caddisfly population may
increase since there is a lot more organic material available for the larvae.
Shedders, predators and scraper species may be prevalent. Stoneflies may not
exist in the less oxygenated warmer water.

The stream’s volume of water and rate of flow is strictly dependant upon Mother
Nature. The amount of water in the stream can vary drastically with the seasons
of the year. Melting snow packs (spring runoff) and heavy rainfall that usually
occurs in the spring months makes the freestone streams large and turbulent
and sometimes flood beyond their normal banks. In the late summer and fall
months of the year, most freestone streams reach their lowest levels.
Sometimes the flow can become so slow and the dissolved oxygen levels so low
that it become tough for trout to survive. This is especially true in the lower
sections of the streams in the foothills.

At the headwaters, most freestone mountain streams support native Cutthroat
trout. These fish are usually small, averaging from six to twelve inches because
they have less space to live and less food to eat but they are also usually very
aggressive and lighting fast. Most of the time, trout found in the headwater
streams feed opportunistically. It is rare that they have enough of any one
species of food to feed on. Selective feeding times are few and far between.
The angler usually does not have to be concerned with specific patterns of flies.
Most of the time, attractor or non-specific type flies that imitate a variety of
insects will work fine.

As I am sure most of you know, rainbow and brown trout are a problem for the
native cutthroat trout. They will compete for the same space and food. This has
forced the smaller cutthroat  trout to exist at higher and more remote locations
than they once did. In many cases, in the middle and lower elevations of the
streams in the Yellowstone National Park, cutthroat trout have been almost
completely been eliminated by the rainbow and brown trout. The park service
along with concerned anglers are working on changing this in a few streams. We
will provide more detailed information regarding this at some point in time.


Copyright 2009 James Marsh