Fly Fishing Cold Water - Part Two
In order to catch trout in cold water, you first need to understand the effects of cold
water on trout. Right up front, I will tell you that the very most important thing to
remember when you are fishing cold water for trout is that the trout tend to avoid
fast water. The colder the water is, the more they avoid fast moving water. In very
cold water, say in the low forties, they avoid it altogether. Here's why.
Cold water reduces the trout's metabolism. As the water becomes colder, both the
energy expenditure and the intake of food is reduced. In water ranging from 38 to
42 degrees, the trout do not need to feed very much at all. They change their
habitat drastically. They seek slow moving water. They will move very little,
if any, to eat. They only need small amounts of food and can actually get by for
long periods of time without eating. The misunderstood part about it is that
presented the opportunity, they will still eat. They will not expend any energy to do
From 42 to 48, their metabolism and need for food increases some. They will still
remain in slow moving water and avoid fast water even to feed. They will
feed, however, provided a good opportunity. They will move very little and then only
in slow moving water to eat.
When the water temperature gets between 48 and 53, their metabolism is increased
to the point you will see them begin to actively feed. Within this range, depending
on the rate of changes in temperatures and the stability of the water temperatures
as well as the particular species of trout, they will again change their habitat
and seek different areas of the stream to rest and feed. At the high end of
this range, it is common to see them feeding, even on the surface and even in
water that is moving quite fast. When it is above 53, you will often see them feeding
in fast water. The more energy they expend, the more they have to eat to provide it.
This doesn't mean they can and will eat anything. It doesn't mean they can always
be caught easily. It simply means they feed more often.
All fish are cold blooded. That means their bodies are basically the same
temperature of the water. Trout are considered a cold water fish. That means they
live in what most people would call cold water. They don't exist and cannot survive
very long in what most people consider warm water. The reason isn't the warmer
temperatures as such, but its affect on the amount of dissolved oxygen in the water.
Very cold water also has an adverse effect on trout. To shorten what could be a
lengthy subject, cold water holds plenty of dissolved oxygen for trout and is not a
factor in what it chooses for a habitat. Cold water can reduce their ability to find and
eat food to the point they lose weight. This has been proven over and over in
western streams that remain near frozen for several month. It has also been proven
that where dams have been constructed on such streams, the overall reduction in
trout loss has significantly been reduced. Studies have been done on that subject.
All trout have a preferred temperature range. That is generally just a made up
range of water temperatures in which the trout do well, eat and grow. For example,
brook trout prefer water ranging from 52 to 56 degrees. They spawn in water
ranging from 40 to 49 degrees. This range, usually stated by anglers rather than
scientist, is often misunderstood and greatly misused as a criteria for fishing. It is
often thought that fishing is poor if the fish are not within found to be within that
range of water temperatures. That is far from the truth.
Different species of trout prefer slightly different water temperatures. These are
very general but should give you an idea of the preferred water temperatures.
Rainbows are usually most active in water ranging from 55 to 60. On the other
hand, brown trout would probably prefer or would be most active in water slightly
warmer that ranging from 57 to 62 degrees. These are the generally accepted
ranges of what is called the preferred water temperatures. Facts are, trout live and
survive well in water that is well out of the preferred water temperature most of the
During the above preferred water temperature ranges, you will find the trout feeding
about as heavily as they will feed. In general, and insofar as water temperature is
concerned, fishing water within these ranges provides the best opportunity or
easiest time to catch them. It doesn't mean you will catch anything. Many anglers
often don't. They just change their excuses.
Cold water has been proven to have a profound effect on the way trout
can swim. It decreases their performance. In essence, they cannot swim as fast.
The trout can also become fatigued much quicker. The acceleration of the trout is
greatly reduced. They no longer have that burst of speed. This is another reason,
they avoid the current and seek areas of slow moving water.
Surface water temperatures tends to change faster and more rapidly than water on
the bottom and in deeper holes and other such parts of a trout stream. They seek
depth for more stability. I have had local anglers tell me that depth made no
difference. They contended the water temperatures are the same throughout the
stream. While this may seem generally true and is certainly not the same as
changes in depths of still water lakes, it is also incorrect. I have spent several hours
taking water temperatures at different areas of the streams in the Smokies and find
that it in fact can be quite different at times. When the water temperatures stabilize
and the air temperatures remain constant over long periods of time, the water
temperatures tend to stabilize There aren't any thermal layers like there are in
lakes, but there can be as much as five degrees or more difference in the water
temperature from the surface to the bottom of a deep hole. Now, don't
misunderstand this. The trout will not seek the warmer water. They do not
feel the cold like warm blooded animals. The only reason this is important, is it
means they may be more active than you tend to think they are.
Changes in water temperatures takes more time to occur in slow moving
water found in a deep pool, for example, than it does near the surface.
Since the trout are holding up in slow moving water, and eat little, they are more
difficult to pinpoint. Unless they are able to see the trout, anglers pinpoint trout in
deep water by strikes. If you get a strike on a nymph, you know the trout is there. If
you don't, you assume they aren't any trout there and try other areas. The problem
becomes finding the trout's location more than anything. As I have said before, if
you are fishing where there are no fish, you need more than my help to catch them.
You need help from the good Lord above.
You can find some deeper holes and areas of slow moving water fairly easy. Usually
these are the ones where the trout can also see you easily. What is tricky about
finding trout in slow moving water in trout streams, particularly in the
Smokies, is much of it is under fast moving water. I will get into finding trout in
cold water in my next article.