Threshold Temps for WW Species

[Swattie87]

I know there's a lot of talk on here about the 68-70 degree cutoff temps for fishing for trout, but what about for warmwater species? It's always just assumed that when the water temps get too warm to fish responsibly for trout, it must be time to fish for Smallies and Sunnies.

I've fished warmwater streams in water temps up to 85 degrees before, and the fish never seemed to be stressed when I released them, but just like trout they too must have a recovery period, and I'm starting to wonder if there isn't some degree of increased post release mortality in these fish above a certain temp. Does anyone know if such a thing occurs, and if so at what temp, generally speaking?

Here's the backstory that got me thinking this...two years ago I was fishing a downstream section of the Swatara in Dauphin county with UL spin gear and Joe's Flies and small twister tails on a light jighead. It was hot that day (August I believe), air temp of 90 or more, and the water temp was 82. I wasn't having a particularly great day, but was still catching fish when I came to a small (maybe 10-12 feet across at its mouth), well shaded trib. I was wet wading that day and immediately noticed a huge temperature difference in the water coming out of the trib. I waded up a little ways and took a temp of 64 degrees. Maybe 30 yards up the trib there was a waist deep hole formed by an old log jam (that has since cleared out) and right as I was about to make my first cast into the hole, I must have spooked the two huge Smallies that were residing there, and they came swimming down the creek channel toward me, almost grazing my leg as they went by. These were 16"+ Smallies, which are very big for the Swatara. Those are a once a year, or less even, fish in that creek. Past that first deep hole the trib really becomes too small and shallow to hold a fish that size so I doubt they were permanent residents of this trib. Coupled with the fact that when I spooked them they fled downstream it seems clear to me they were there temporarily for the cooler water. Just got me to thinking...

 

[jayL]

They may have preferred the cooler temps of the tributary, but I think it's more likely that they were after the food and the shade.

 

[greenghost]

Smallies especially are shade junkies. imo, they are more light sensitive than even trout, providing temps are tolerable.

 

[troutbert]

I have a related question. How warm do warmwater rivers get in PA when water levels are very low and air temps get very hot?

I took a temp of 90F on Middle Creek, and also 90F in the Susquehanna near Marysville. I heard that the Susque goes as high as 100F.

What is the warmest water temp you've measured? (Not counting hot water releases from industries or power plants.)

 

[JackM]

Bass seek out the warmest water available during winter. There is little or no feeding activity by largemouth of smallmouth in temperatures less that 50 F and no growth occurs. Digestion occurs 6 times faster at 77 F than at 44 F. Initial spawning activity, like nest building, will begin when temperatures climb to 60 F. Actual largemouth spawning occurs at 64-66 F while smallmouth spawn at temperatures 4 degrees cooler. Maximum growth rates are achiever at 80 F for largemouth and 78 F for smallmouth.

Smallmouths prefer cool, clean, clear water and are not fond of muddy or dirty water systems. They like temperatures in the 65° - 72°F range and moderate current (in rivers) and are usually found in deeper water than largemouths (in lakes). The lethal water temperature for smallmouths has been calculated to be about 95°F.

 

[Swattie87]

You guys could be right on the shade theory. When fishing for them I do tend to focus on shade/sunlight boundaries. I doubt forage was the reason they were up that trib though. The bottom in the mouth of the trib is mostly mud/silt where as the main stem of the Swatara is a run/riffle/pool gravel/boulder bottom with lots of crayfish. There were some small Sunfish in the trib, but from my experience big Smallies don't focus in on them as a primary food source the way big Largemouth tend to. I would think the crayfish and juvenile Fallfish and Chubs in the main stem would be the primary food sources for big Smallies in this stretch.

I'd be interested to know if a Smallie would prefer 82 degrees and shade, or 64 degrees and sun, forage being equal.

troutbert wrote:
I have a related question. How warm do warmwater rivers get in PA when water levels are very low and air temps get very hot?

I took a temp of 90F on Middle Creek, and also 90F in the Susquehanna near Marysville. I heard that the Susque goes as high as 100F.

What is the warmest water temp you've measured? (Not counting hot water releases from industries or power plants.)

The USGS site in Harrisburg on the Susky used to keep temperature data, although it looks like they may have stopped. I've seen it over 90 in the summer...I'd bet there are some local spots that get even hotter. 85-86 is the highest I've ever personally gotten on a thermometer...below the last of many impoundments on a warm water trib of the Swatara.

 

[Swattie87]

JackM wrote:

Bass seek out the warmest water available during winter. There is little or no feeding activity by largemouth of smallmouth in temperatures less that 50 F and no growth occurs. Digestion occurs 6 times faster at 77 F than at 44 F. Initial spawning activity, like nest building, will begin when temperatures climb to 60 F. Actual largemouth spawning occurs at 64-66 F while smallmouth spawn at temperatures 4 degrees cooler. Maximum growth rates are achiever at 80 F for largemouth and 78 F for smallmouth.

Smallmouths prefer cool, clean, clear water and are not fond of muddy or dirty water systems. They like temperatures in the 65° - 72°F range and moderate current (in rivers) and are usually found in deeper water than largemouths (in lakes). The lethal water temperature for smallmouths has been calculated to be about 95°F.

Good info Jack, thanks.

 

[Fishidiot]

I'm not sure of the hottest temps I've recorded but I have certainly seen 90s in shallow, slack water areas of large rivers. The lower Juniata was 86 the other day (I took two temp readings in the shade to verify) and fishing was slow. On the other hand - in my experience - fishing for smallmouths is often very good with water temps in the 80s. Looking thru my old fishing records indicates a lot of good days of river bassin with temps in the 80-85 degree range. I'm not sure about temps much above about 87 but I suspect this is the upper range in which one can expect good bass fishing, esp for larger fish. Oxygen levels at that temp may also be on the lower side and a C&R fisherman perhaps should use some caution. There was some discussion on this board last year regarding this issue due to the extremely hot, low water conditions we had last summer (last year was probably my worst year for bass fishing).

Ditto on the shade effect.

 

[afishinado]

Fishidiot wrote:
I'm not sure of the hottest temps I've recorded but I have certainly seen 90s in shallow, slack water areas of large rivers. The lower Juniata was 86 the other day (I took two temp readings in the shade to verify) and fishing was slow. On the other hand - in my experience - fishing for smallmouths is often very good with water temps in the 80s. Looking thru my old fishing records indicates a lot of good days of river bassin with temps in the 80-85 degree range. I'm not sure about temps much above about 87 but I suspect this is the upper range in which one can expect good bass fishing, esp for larger fish. Oxygen levels at that temp may also be on the lower side and a C&R fisherman perhaps should use some caution. There was some discussion on this board last year regarding this issue due to the extremely hot, low water conditions we had last summer (last year was probably my worst year for bass fishing).

Ditto on the shade effect.

Agreed on all points. Fishing can be good in higher temps (80's), but when SMB fishing, on hot days I usually look for water with a decent flow and/or shade from the sun. The early morning or evening fishing is often tremendous.

I also agree that last year was the poorest SMB season I can recall. I surmise the temps were too high for long stretches of time (a record fifty eight 90*+ days last summer in SE PA), putting the smallies in a funk on many/most days.

 

[greenghost]

JackM wrote:

There is little or no feeding activity by largemouth of smallmouth in temperatures less that 50 F and no growth occurs.

The biggest bucketmouths on Lake Arthur are often caught through the ice in February and early March. (Not to poke "holes" in your source... ba-dum.)

 

[BPS]

GreenGhost- It does seem the bigger ones do feed in the colder temps. Maybe they have to to maintain their size, because I never caught many small bass in cold temps. I have caught some nice sized smb in the little j in february/march.

 

[JackM]

Probably the terms "little or no" to describe "feeding activity" were poorly chosen by the author.

I agree that fish must feed all year round. In the extremes of temperature, however, their metabolism slows, and they eat only enough to maintain health/life, typically losing some weight or staying the same, but rarely gaining weight over a winter.

During a fishes growth months, "feeding activity" takes on a slightly different meaning, and I suppose the author had typical "growth period" activity patterns in mind. That particular article was more about fishing than biology, but I thought it answered some of the questions and would get the OP on his way to further discovery.

Ice-fishing involves dangling the offering in about the same place for hours on end. Eventually, if there is a fish nearby or passing by, it isn't going to pass up an easy meal and you'll get a strike. "Whoopee, pass the bottle!"

 

[brain]

the warm water fish are also more robust than the trouts...which in imho are fragile.