Deep holes in streams and most rivers vs temperature

[franklin]

Just to stir the pot; remember that fish are cold blooded and we are warm blooded. So "felt" temperatures likely vary.

 

[Reeder]

Most of the energy from the sun is absorbed at the surface. The deeper you go, the less energy is being absorbed from the sunlight. The energy is constantly transferring in the water to get the uniform temps that Mike is talking about. He is right, depth and depth alone in a stream or river will not create significantly cooler temps without another influence like a cooler trib or cold spring. However, depth could provide summer refuge, not because of the cooling it provides, but because of the prevention of warming. Water temperature isn't the only thing that affects the trout's body temperature. Water takes a long time to heat and cool. The sun will warm a trout, just like it warms the water, just like it warms anything else it touches, but faster. The closer to the surface the trout is, the more energy it will absorb directly from the sun.


Wouldn't a rise in body temp cause a rise in demand for dissolved oxygen, and couldn't a fish still die at too high of a body temp even though there is plenty of dissolved oxygen?

 

[Cold]

I'm glad nobody looks to find some shade in the heat of summer, because they know it's just as hot under the trees as it is out in the open!

More to the point, I'm glad you let me know that the shade isn't any cooler than being out in the sun...all this time, I've been looking for the shade for no reason.

 

[Chaz]

afishinado wrote:


Flowing water constantly mixes and doesn't allow stratification. Until Mike posted this, I thought this was common knowledge and universally accepted like gravity or the Earth moving around the sun.

Next you'll be telling the Earth is round and not flat. Sheesh!

 

[jifigz]

afishinado wrote:

Cold wrote:
Radiant heat vs conducted heat.

Kinda like how on a winter morning, there will be frost in the shadows but not out in the sun, even though the overall air temps may be the same.

There's not a study out there that will convince me that the bottom of a deep pool isn't colder (in warm weather) than the surface. It just isn't so. In very cold weather, the opposite will be true, as the ground will help to insulate the deeper water from the colder temps caused by the air at the surface.

Mike wrote:
..in the Delaware R in Phila where the water is 40 ft deep, the summer temp difference from surface to bottom is 0.1-0.2 degrees C.

You don't need a study....just a thermometer! And ^ that's in 40' of water1

Flowing water constantly mixes and doesn't allow stratification. Until Mike posted this, I thought this was common knowledge and universally accepted like gravity or the Earth moving around the sun.

Amen. I thought all fishermen knew this. Obviously it depends on the streams gradient and characteristics. A stream that has an extremely low gradient and almost no riffles and runs may have a slight difference, but a stream with a high gradient and a lot of mixing will have no real measurable difference. The brookie streams I fish in the summer with a ton of mixing going on I am sure the same at 2 inches deep and at the deepest depth of 4 feet or so.

 

[PennypackFlyer]

Which is more important: temperature or oxygenation for their survival? When I have a fan blowing on me it feels cooler - it's still the same air temperature however more oxygen is being pushed my way.

 

[pcray1231]

Dissolved oxygen content is more important.

But you will find that oxygen content and water temperature are very well correlated. Cold water holds more oxygen. Above a certain temperature, you CANNOT dissolve enough oxygen.

I think you'll also find that most all flowing waters are more or less saturated to their maximum dissolved oxygen content for the water temperature.

The only time you really get significant differences between how much oxygen the water CAN hold and how much it actually does hold is in still water that is well stratified and does not mix. That does happen on occasion, for instance in some ponds you get die offs if mixing is not present as algae consumes the oxygen in the bottom layers and the surface oxygen is not sinking. Or in areas where freshwater enters saltwater (the saltwater sinks and often stays deep with little mixing), you get a dead zone on the bottom, for instance in the upper Chesapeake or in some places around the Mississippi delta.

 

[PennKev]

PennypackFlyer wrote:


Which is more important: temperature or oxygenation for their survival? When I have a fan blowing on me it feels cooler - it's still the same air temperature however more oxygen is being pushed my way.

This is flawed logic.

The cooling affect of a fan blowing air at you has nothing to do with oxygen except that oxygen happens to be a component of air. Fans work by accelerating evaporation and convection by moving "fresher" air across your body and blowing away air that has reached high temperature and humidity due to proximity to sweat and body heat.