Weather/Water Temps and Trout

[Stagger_Lee]

I have read that the prime time of year to fish for trout is April, May, June, due to the normal temps and water temp. Is this true? Do the trout die off as the temps of the water get warmer?

If so; how do you guys think this warm winter/Spring will affect them this season?

 

[pcray1231]

That is generally true. But you have to realize that there's thousands of wild trout streams in this great state, and they vary greatly on seasonal water temps.

You have the limestoners, which have fairly constant year-round water temperatures closer to the springs, but many flow a long distance and eventually succumb to heating. You have freestoners. The smaller ones generally stay cold year round, the bigger ones warm in the summer, and the medium ones are somewhere in between.

In either case, how big or far from the springs you can go is governed by many factors such as gradient, width of stream, whether the banks are shaded or not, altitude, etc.

And then you have tailwaters, and the water temps on those vary based on the depth of the lake, whether the dam is top or bottom release, and how flows are regulated. After all that is figured out, then it goes back to the aforementioned factors.

It's really not as hard as it sounds to figure this all out, it's all logical. But it makes generalizations problematic. Take each stream as a separate entity.

I just told you not to generalize, and I'll go forth and generalize anyway! We've been very dry, but don't look now, we just had a colder than average April! The low flows are hurtin the small stream fishing and helping the big stream fishing right now. For concerns about summer, though, going in with low flows is not a good sign for either. Of course, it could turn wet in a hurry. I'll take a dry spring and a wet summer any day of the week. But a dry spring and a dry summer would be bad.

 

[RCFetter]

I guess you can't generalize. I've done a little superficial research on warm water temperature and trout survival and can't find a definitive statement.

Just recently I discovered a blog by a Philly area fly fisherman who states that the Pennypack in Philly or at least in Montgomery county has holdovers. I've been told or have read that trout can not survive the summer in the Pennypack.

So I guess trout can survive in a warm water stream if they can find cold spring sections to survive in. I'm just guessing. I really don't know.

 

[Volksnurse]

I know a couple deeper holes in the PP that I've gotten smaller trout and holdovers from as late as december. They're not in the more heavily traveled areas and not very frequent.

 

[Pauly]

For some reason I have 80 degrees Fahrenheit in my head as the trout temp to go by.

I'm not sure if that is the absolute no go for trout (death is near) , or the temperature they start migrating to cooler water if its available.

 

[Swattie87]

70 is usually about the number most folks associate with heat starting to stress trout, probably a few degrees less for Brookies. As the temps rise past 65 into the upper 60's trout will start to look for cooler, more oxygenated water...deep shaded holes, spring seeps, colder feeder tribs, heads of plunge pools, etc.

IIRC correctly the lethal temp for Brookies is about 72, and about 75-76 for Bows and Browns. Could be off by a degree or two there, but that's pretty close I think. This can vary a little bit based on the amount of dissolved oxygen in the water (more DO means higher temps can be tolerated), but again, not by much.

80 would be lethal pretty quickly to all three species found in PA if they couldn't find cooler, more DO rich water.

 

[pcray1231]

70 F is the figure that is more often thrown around. Not saying 70 F is "death" temperature. It's just often the temp thrown around that you shouldn't fish above.

I don't think you can put a finger on an exact "death" temp. Maybe you can but it would rarely come into play in reality. For instance, how long it stays there is a big factor. If it's goin up to, say, 72 in the daytime but recovering to the mid 60's at night, those fish might be able to handle that for a while. But if it's goin up to 72 and staying there, that's extreme stress and if that goes on for any length of time those fish are in trouble. As you get up from there, then the window on how long they can handle it shrinks.

Further, some streams have cold water springs or tributaries where they can escape the heat. Some don't. And some streams are faster than others, those riffles force oxygen into the water.

I believe they typically die from lactic acid poisoning rather than suffocation. Like us, when they get too little oxygen their respiration becomes anaerobic to produce energy, which produces lactic acid as a byproduct. Lactic acid is how we get sore muscles. They do essentially the same. And they can handle it for a little while. But when there's no escape, it just builds up, makes them sick, and they die.

Come summer, you'll hear a lot on this board telling you to leave stressed fish alone. A fight on the end of a line really takes a lot out of them when they don't have a lot to spare.

 

[Swattie87]

Just did a little Googling, and I was probably a little low on my recollection on the lethal limits...more like 75-76 for Brookies, and 78-80 for Bows/Browns. Again, those aren't hard numbers necessarily, as there are other factors at play...DO in the stream in question, daily temperature swings, etc.

In any case 80 would be a serious issue for them. Fishing for them in water temps above 70 or so also significantly compromises their ability to recover when released.

Edit: ^Good post by pcray in the meantime.

 

[RCFetter]

Pcray stated the most meaningful stat. To paraphrase as a rule of thumb, if the temp is above 70 don't fish...but if the temp is above 70 on a sunny day it should drop into the sixties as the sun sets and trout will feed.

 

[Stagger_Lee]

Thanks - some interesting stuff here.

 

[Fishidiot]

Yep - what Pcray said. Once it hits about 70 I don't practice catch and release trout fishing.

The local trout streams around here (Adams Co) get too warm to hold trout during summer and there are few or no cold water refuges. By June, temps are usually in the 70s by mid day. When it gets this warm, I'll go out in the morning when it's a couple degrees cooler and try to catch and keep my limit as these stocked fish will die off within the next few couple weeks or months at most.