PH meter:
In the late 70's I fished the
professional B.A.S.S.circuit. I
remember meeting Dr. Hill, an
avid bass angler who invented  
the electronic pH meter that you
mounted on your bass boat. It
gave an instant readout on the
pH of the water. Anglers
thought they had a new
instrument that was a big key in
finding bass. I believe Darrel
Lowrance (Lowrance
Electronics) was the one who
first introduced it for Dr. Hill.
I did not know a competing
angler that was not given one
or didn't purchase one. We
knew the best pH for bass was
slightly alkaline so in the 3 day
practice period we would run all
over the lake the tournament
was held on looking for water
with a high pH. The plan was to
eliminate the water with the
lower than preferred pH. In
almost all of the lakes we
fished from coast to coast, the
problem with the new pH meter
soon became obvious. We
could find no bad water. It all
had an acceptable pH level. I
guess that is why Dr. Hill's or
Darrel Lowrance's pH meter is
not around today.
I don't think it will help you to
catch trout by going all over the
park measuring the pH of the
water. It will help you to
understand the role  pH plays
in the streams trout and aquatic
insects habitat.  It will also help
you to understand one of the
problems marine biologists are
confronted with in their efforts to
restore the native species to
their original habitat.
pH Scale:
............................Fly Fishing Yellowstone National Park
The water in most headwater streams in the park
(as well as other headwater streams) is more
towards the acidic side of the pH scale than the
alkaline side of the scale. Water below the normal
pH scale of 7.0, almost always contains less
aquatic insects than water that is average or on the
high side such as that found in most spring
creeks. Less aquatic insects generally means
there is less food for the trout. Less food means
the streams will have smaller trout.
When the unpolluted rain and snow falls from the
sky it is pure and free from minerals. It is slightly
acidic and has a pH of approximately six. This
does not take into consideration acid rain which is
a big factor in the pH level.
As the water flows downhill, the pH will usually
increase depending upon the type of rocks, sand,
gravel, and organic material (such as leaves and
vegetation) the water passes through. The pH of
the headwater streams varies from region to
region depending on the plants and the
composition of the soil and rocks. Rain forest type
terrain, such as is found in the Appalachian
Mountains, provides the water a different chemical
composition than the more barren slopes of the
Rocky Mountains. If the water passes through
volcanic rock, it is going to remain acidic much
longer than water passing through a forest.
Those of you that have a swimming pool that you
maintain are very familiar with the pH of water. In
this situation you don't want water that is on the
alkaline side of the scale because it supports the
growth of the things you have to clean from the
sides and bottom of the pool Those of you that
have an tropical fish aquarium are also probably
very familiar with pH. If water in the aquarium gets
off the desirable level  very much you and the fish
will soon know it.
pH is not the only factor important for fish. It is just
one of several. Facts are where streams have a
high pH value above 7.0, such as spring creeks,
the trout grow to much larger sizes than they do in
water with a low pH value.
The different pH values of the water from its origin
in the mountains to the larger streams or rivers in
the valleys supports different groups of aquatic
insects. The water temperature is generally higher
in the lower sections of the stream and this can
also be a factor that affects trout in that it changes
the insect population. The speed of the water is
also a big factor in determining which aquatic
insects exist.
Because the water is usually fast moving pocket
water, mayflies found in the headwaters are
usually clingers. Caddisflies are not very plentiful in
these waters because of the acidic level of the
water and consequent low algae levels. Many
species of stoneflies are in their prime habitat in
the highly oxygenated water. This water may not
support plant life such as algae. The aquatic
insects must rely on other source of food.
When the stream becomes the "run, pool, riffle"
type of stream, normally found in the lower
elevations, the more diverse type of water will
usually support many other species of mayflies,
caddisflies and stoneflies. Mayflies may include
several species of crawlers and swimmers. The
caddisfly population and diversity will increase and
include many species of scrapers, predators, and
shedders due to the diverse type of habitat.
Stoneflies are still usually present in the fast water.
Since the water has poured through rocks, gravel,
sand and other types of soil and since organic
material such as leaves may have accumulated in
the stream, the water is less acidic than it is in the
headwaters. It will normally support species of
aquatic insects that rely on organic material that
has become more prevalent due to the higher PH.
Its increased temperature is also conductive to
supporting other insects.
Streams like the Madison and the Firehole Rivers
have a high pH and therefore support a very large
insect population. The headwaters of small creeks
such as Larva Creek may have a much lower PH
value than the streams at the lower elevations. One
indication of a high pH stream is whether or not it
has any vegetation. If there are weeds and grass in
the stream, it probably has a pH above 7.0 or the
water is slightly alkaline.

Copyright 2007 James Marsh
Brook Trout seem to be more
tolerant of acidic water than other
species of trout. My guess is that
the char became that way over a
long period of time (thousands of
years maybe). I don't think they
became tollerant of the extra acid
that got into the water when
construction workers cut a road
through the anakeesta rock
formations in the park or when
man polluted the air to the point it
caused acid rain to occur.