Temperature Induced Feeding

**Adam** · 01-19-2009, 08:08 PM

Ok...so with all of this lousy weather I have been working far too much, but I have also been doing a lot of reading. I came across this topic after cracking open Osthoff's No Hatch to Match book.

Temperature Induced Feeding Binges....

"But it is also a good bet that you'll bump into your largest and most aggressive trout during the non-hatch periods? Why? Because it is usually an invigorating water temperature [i]not a hatch that puts predatory trout on the prowl."

Interesting...thoughts anyone?

**Nymphmeister** · 01-19-2009, 09:45 PM

Yeah, I mostly agree with that statement. Often temperature swings in a positive direction turn the trout on & get them feeding- e.g. a milder Winter day. I suspect it also increases the activity of the insects underwater too.

alanb_ct · 01-19-2009, 09:52 PM

In the summer, right after a warm thunderstorm rain, but before the water gets much higher, I have seen increased activity. Aaron and I witness this first hand last summer on the Farmington.

Both of Osthoff's books contain some real out of the box thinking, and descriptions of some awesome Wisconsin trout fishing.

**Adam** · 01-20-2009, 11:13 AM

on the same topic...I have read that...

it is not that the temperature of the water itself is in the optimal range, but rather a movement towards or away from the range that can stimulate the trout.....

I need some ice to melt soon

**Davyfly** · 01-20-2009, 12:19 PM

The major influence that often as not determines fish feeding activity is the influence of light as this is also very much related to food base activity.
Light source is also related to temperature, days of diminished light differ from those of good overhead light conditions, which as a rule also raise temperature.
Typical days during the winter periods will see fish more so active if we see a rise of a few degrees of temperature that often as not is during the afternoon periods.
But that may not be related to the fact that there is also a active food source.

During the colder winter periods with a few exceptions such as chironomids invertebrate food sources are largely dormant.
The vast majority of bottom dwelling organisms are way more active during days of diminished light and during the warmer periods of the year at night, which also coincides when trout, particularly Browns are more so actively feeding.

Rainbows by far prefer days when there is a greater presence of light, Browns on the other hand generally prefer days when there are conditions of diminished light sources.

There are also many other issues to consider here.
The process of photosynthesis is of course a related issue to the presence and penetration of light, levels of oxygen in a body of water will increase, which is a stimulus for trout to become active.
Rain fall may increase water temperature as often as not rain is warmer than the body of water it falls to, it also agitates that water surface and increases DO levels, often as not we do see increased surface activity from the fish at this time, all be it no hatch is taking place. This can be very common for stillwaters.

I know of rivers that despite the fact there are hatches of many species taking place, not a fish will be seen feeding, regardless of what climatic conditions are taking place.

There are many trains of thought that consider changes in barometric pressure are related to fish feeding activity, no doubt in my mind that this can be the case, but l cannot give you a answer why, all be it there has been a great deal of research undertaken to try and understand this.

Bottom line is this, temperature changes may have no influence so far as hatches or food base activity, all be it the trout become active.
On the other hand temperature related issues may have some influence for specific species.

It is a very interesting subject matter no doubt, and one we do not as yet fully understand.

DW

**Nymphmeister** · 01-20-2009, 03:46 PM

I remember learning an old rule about fishing for trout, and it's been at least 90% true for me here in the Northeast:

"The most comfortable time of day is the best time to trout fish".

In the late Fall, Winter & early Spring that equates to early to mid afternoon, and if a hatch occurs (with a few exceptions, e.g. Winter Caddis in mornings on the Farmington) it usually is in this same time period. Air temps are generally cold at that time and water temps are usually in the 30's to 40's in our local rivers & streams, and this time of day sees rising water temps, with a movement toward optimum temps (mid 50's to mid 60's).

"Prime Time", in mid Spring can see good fishing almost all day, water temps are typically in the 50's to upper 60's, air temps are comfortable. Caddis will typically hatch in the mornings and egg lay in the evenings, Mayflies will mostly hatch in the afternoons & evenings. As it gets warmer, hatches will start to push into the mornings & especially the evenings. Mayfly hatches, spinner falls, and Caddis egg laying will be heaviest in the low-light period of dusk.

Late Spring thru late Summer will see most waters warm beyond optimum trout temps at moments (tailwaters & Spring Creeks excepted), and in some places they will hit lethal levels if the trout cannot find cooler water & more oxygen. Both insect hatching activity and trout feeding occur at the coolest parts of the day- early, late & at night. These are also the most comfortable times for us humans. One exception can be terrestrial insects, they are most active in hotter weather and can create good midday feeding if the water isn't too warm.

As things cool in September, sometimes the fishing is good all day, although there will still be some warmer days with the best fishing right at dawn & dusk. As it cools down more & we move into the Fall, afternoons are usually the most comfortable temps & the best time slot for fishing. This is also when you typically see the best hatches.

All of the above is mostly true of freestone streams- Tailwaters & Spring Creeks often operate on a somewhat different set of rules due to the more stable nature of the fisheries, in terms of flows, temperature changes, and food base. And certainly as Davy mentioned, light conditions can have a big effect on things. All things being equal, if water temps are optimum (mid 50's to mid 60's) I still generally have my best fishing in low light conditions and see the best insect activity at those moments too. This is especially true of brown trout, and even more so if you are talking BIG brown trout!