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Posts: 1906
Location: Oconto Falls, WI | For those that think the water is cooler just a few feet down take a look at the water column profile taken on Jul 10 of this year on North Twin Lake. On top of that a cool night or two isn’t going to change the water temp all that drastically when it is this warm that far down.
A quick warm up with water temp spikes is one thing for the water being cooler just a few feet down. But a summer like this year is much different.
(NTwin-Water-temp-Jul102012.jpg)
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 NTwin-Water-temp-Jul102012.jpg (93KB - 196 downloads)
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Posts: 32803
Location: Rhinelander, Wisconsin | A half inch of cold rain from a big thunderstorm can drop the temps by 5 degrees if the evening and night is then cool and the storm cloud top is up there high enough to draw down cold air rapidly. Three days of cooler weather where the temps ay night are 50's and daytime weather is cloudy or partly cloudy and it's a little windy can drop water column temps by quite a bit, because cooler/cold water sinks immediately and mixes with the entire column on the way down until equalized.
The water temps on Bay of Green Bay all the way out in 30' dropped 8 degrees after a big storm recently, but several hot days and nights brought it back to mid 70's.. That HUGE body of water is even warm right now, warmer than most can remember seeing it.
No long term relief in sight through the first week August. |
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Posts: 1764
Location: Ogden, Ut | Interesting. The water is holding it's temps pretty effectively even at depth...looks like there's a bit of an oxygen-temperature squeeze going on there too. Cool data.
One caveat though, it's just one lake, and although many will act similarly, each will have their own characteristics and will exhibit those according to the physical parameters they are subject to.
S. |
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| Worthy of note is that the DO is highest at the surface during the warm water period.
BrianF |
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Posts: 1906
Location: Oconto Falls, WI | Brian with the warm temp I am not concerned over D.O. levels what-so-ever. If you look at other lakes you will also find some that the D.O. levels for whatever reason are actually higher 15-20' down then they are on the surface. Oxygen is only one piece of the mortality puzzle.
I found some lakes the water temp was still 80° 15' down or so! You would expect then that the surface was really high, but that is not the case. Going off memory the surface temp was only like 81.5°.
My point being in all of this is don't think or expect the water to be a lot cooler farther down in the water column as it just isn't the case on a lot of lakes. |
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Posts: 32803
Location: Rhinelander, Wisconsin | This IS an extreme exception to the rule though. Been a very long hot streak, setting lots of records.
A break is on the way for us up here, rain and cool temps with a high in the 70's Wednesday and low in the 50's for a few nights. Might be OK for a few days on some water until it heats back up. Looks like it will heat back up.
Worse than Winternet. people are losing it. |
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Posts: 1906
Location: Oconto Falls, WI | sworrall - 7/23/2012 8:41 PM
This IS an extreme exception to the rule though. Been a very long hot streak, setting lots of records.
A break is on the way for us up here, rain and cool temps with a high in the 70's Wednesday and low in the 50's for a few nights. Might be OK for a few days on some water until it heats back up. Looks like it will heat back up.
Worse than Winternet. people are losing it.
Yes this year is an exception on how long we have had this high heat. However it is not an exception on how far down the water column gets heated. Look at some lake data through the years. Here is North Twin for the last two years prior to this year and you will see the same trend that the water stays very close to the surface temp up to 20' down.
(NTwin-H2O Temp 2011.jpg)
(NTwin-H2O Temp 2010.jpg)
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NTwin-H2O Temp 2011.jpg (88KB - 166 downloads)
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Posts: 582
| Every lake is different. Water clarity, movement etc.... Flowages with moving water appear to be cooler 2 feet below the surface. Just because one lake is warm doesn't mean they all are. Take a look at the lake you plan to fish. |
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Posts: 1023
| This is a great graph, Cisco, thanks for posting. I'll be checking out the lakes that I want to hit this coming weekend. |
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Posts: 331
Location: Stevens Point, Wisconsin | Hey Travis,
This might answer a question I have had for a couple years.
When guiding up on the woods I would of course talk with the walleye guides. In mid Aug on the deep isolated reefs, the largest walleyes in the system would be found concentrated around the reefs in great numbers. Of course as with the case with muskies using solar heat gain on shallow rocks, I was told that the late summer warm up of deep reefs is what causes these big walleyes to migrate from the expansive mud flats to deep rock. The guides would always tell me that the deep rocks heat up just like the shallow rocks. I was a little skeptical because I always thought that there was no way the sun could penetrate down 20 feet. Possibly the warm water temps at that depth is enough to warm the rocks?
From your charts it's interesting to see the warm water temps that deep. Maybe I found my answer?
Of course that bite only will last about 2 weeks as the days become shorter and nights cooler in late Aug, but when it's going it can really be impressive.
Ed
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Posts: 432
Location: Eagan, MN | Very interesting data. I wonder what time of the day the the data is collected? I don't think 78.7F is THAT hot, and I think most would still fish at those temps. If that is morning surface temp on a 95 degree day, you could easily see low to mid 80's by late afternoon. Meanwhile is it still 78 degrees 6' down? I noticed that the shallowest readings are 3' down. It leaves a lot of questions, but I think CK's point about extended hot streaks is well taken. |
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Posts: 5874
| I'd bet that the Thermocline(ThermoRefuge) affects the water column temp quite abit. Just like turnover, but opposite. Once that thermo cline is established, the water column above it will turn and equalize.
That's my theory, and I'm sticking to it.
Notice the DO drop off the edge between 20-25' this Jukly? Some of the other years it was 25-30? That is where the big girls will reside, right at the Thermo Refuge.
Edited by Shep 7/25/2012 4:27 PM
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Posts: 8729
| Regarding DO levels and mortality...
Interesting to see D.O. levels highest at the surface. Could the delayed mortality we see in the warmest temperatures be a result of the fish trying to find cooler water, at a temperature that only exists BELOW the thermocline, where there is not enough dissolved oxygen for them to recover from being caught? Let's look at the 70 degree mark. In a normal year, there is plenty of oxygen where you find 70 degree water temps, even during the hottest part of the season. Now look at this year...
If the processes that remove lactic acid buildup are the same in fish as in mammals, you need oxygen, and lots of it. It's why we are out of breath after vigorous exercise.
Make me wonder if the best thing for releasing a muskie in warm water temps would be to keep it near the surface instead of thinking we're doing ot a favor by returning it to the depths. |
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Posts: 432
Location: Eagan, MN | It's true that the POTENTIAL amount of D.O. diminishes as water temps increase, but that doesn't mean D.O. is necessarily lower in warmer water. Simply look below the thermocline for evidence of that.
*Speculation Disclaimer* --I suspect that the oxygen requirements of the fish itself increases as it's body gets warmer, along with probably several other heat-related physiological problems. Perhaps 9 mg/l may be adequate at 75F, while 9 mg/l at 85F is dangerous. |
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| From some recent research of mine I have come to the understanding that fish mortality probably doesn't have much to do with oxygen levels and more to do with an increase in the fishes stress response. However the previous post brings up an interesting point that I will have to research more. |
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Posts: 1828
| CiscoKid, or anyone else, can you post a link to those temperature profiles?
I can't believe I found this thread. |
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