What is too warm?

Smalma

Active Member
#1
Here in western Washington with the recent hot spell our local lake temperatures after a prolong cool spell are soaring. When do folks say enough is enough and end their lowland lake trout fishing until the fall? What is your temperature thresholds?

I visited Pass yesterday and found that the surface temperature had raised to 71 degrees (at 10 AM) up 5 degrees in the last week. Of more concern Pass is a shallow lake; most less than 20 feet deep. I ran a quick temperature profile and found that 70 degree water extended down to more than 10 feet and even at 20 feet the bottom 4 or 5 feet of water was 66/67 degrees. I did fish but tried to land the fish quickly (actually broke one off and pulled several hooks) and minimize any handling. The fish fought well (several making the backing) and did not appear to be unduly stress. However have decided to call it season for the lowland lake trout season and am ready to move on t0 various warm water species, rivers, and Puget Sound opportunities.

At what point do others make similar decisions?

Curt
 
#3
Even in deeper lakes that have a thermocline, the temperature of the surface layer (the water column from the surface down to the thermocline) won’t change that much. Temperature monitoring has shown as little as 2 degrees depression down to the thermocline from the surface.
 

Starman77

Active Member
#4
I generally say that 70 degrees is the high temperature limit for rainbow trout. Above that and the risk of unintentional mortality increases greatly even with careful C&R techniques. But, it depends on the lake too, as some lakes with good depth may provide better conditions for the fish, or strong underwater springs may provide cooler water and more oxygen, or shade from trees or cliffs may help the fish stay cooler. I recommend going higher in altitude where the lakes take longer to warm up (think Leech Lake at 4,000 feet or high altitude BC lakes in the 3,500 to 5,000 feet range). Another alternative is to fish for the Lahontan Cutthroat, as they can tolerate the warm water temperatures a lot better than rainbows (think Omak or Grimes). Or fish for different species (think shad or bass or pink salmon late summer in odd years).

Several years ago a friend had a fish finder that read the temperature at various depths. Here is the chart he produced from Grimes Lake one summer:

Water temperature gradient chart.jpg


I'm sure some lakes are different, depending on a lot of factors, but at least at Grimes Lake, the temperature at the surface was substantially different than the temperature in the thermocline (which was about 24 feet down).
 
#5
From looking at the graph it looks like the point of inflection of the temperature was about 67-68 degrees which on that day is most likely where the thermocline was. Still only a 5 degree difference from the surface temperature. I agree that different species such as Lahontans can tolerate higher temperatures since they evolved in that environment.
 
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Irafly

Indi "Ira" Jones
#6
Stoked trout. I understand wanting to limit your impact, but at the same time these fish, even in Pass are just stoked trout. Yes with higher temperatures, you end up with more evaporation of dissolved oxygen and the fish's metabolism increases, thus creating a need for more oxygen. Windy days will then be better than dead calm days. If I find a time to fish in the Summer at Pass, I will.
 

Starman77

Active Member
#7
From looking at the graph it looks like the point of inflection of the temperature was about 67-68 degrees which on that day is most likely where the thermocline was. Still only a 5 degree difference from the surface temperature. I agree that different species such as Lahontans can tolerate higher temperatures since they evolved in that environment.
I'm sure the thermocline level can change from day to day and even in different parts of the lake, depending on underwater springs or inlet creeks, and maybe wind (as Ira points out, although it seems to me that it would take an awful lot of wind over a fairly long time to change the dissolved oxygen content down at 24 feet). I identify the thermocline layer by not only where most of the fish are holding, but also by the sonar reflection on my fish finder. At least at Grimes on most parts of the lake, that thermocline layer is usually at 24 feet.
 
#8
I have been a lake steward on a small King County lake the last few years. Measured water quality, visibility, temps, etc. every two weeks spring thru fall. It is fairly deep for it's size ~50'. The surface temp (3' down) got up to 75 degrees. At 20' feet down the water stayed at a fairly constant 55 degrees due to depth and all the natural springs. I noticed bringing up the fish from ~15 to 20 feet down was hard on them due to temps and lack of O2. So I quit fishing last season when the near surface temp was above 65 degrees. I will stop earlier in the season this year; especially with this heat wave we are having.

I know each lake is different but when nice, healthy fish show lots of fatigue/stress when fighting before the release it is time to wait until fall when the temps cool down...
 

Krusty

Active Member
#9
As others have alluded, temperature is just one aspect....every lake exhibits seasonal thermoclines....but the real kicker is what's the dissolved oxygen level in that colder dense summer hypolimnetic layer? It could provide a refuge if sufficient, but without a DO probe it's anybody's guess regarding potential lethality.
 
#10
Make it easy, fish for Bass, panfish, or Carp this time of year. By this time I am ready for some warm water fun.
Trout and Salmon are way overrated. ;)
 
#11
It has been my experience that once the top few feet reach 70+ degrees the survivability rates are not very good. Although I have seen 8lbs "rest" on the bottom for a while before swimming away. At two sleepy fish, resting in the weeds, I call it a day :rolleyes:

Science ;)
 

bakerite

Active Member
#13
Stoked trout. I understand wanting to limit your impact, but at the same time these fish, even in Pass are just stoked trout. Yes with higher temperatures, you end up with more evaporation of dissolved oxygen and the fish's metabolism increases, thus creating a need for more oxygen. Windy days will then be better than dead calm days. If I find a time to fish in the Summer at Pass, I will.
I love catching the "stoked" trout too Ira!

"stoked" is to be completely and intensely enthusiastic, exhilirated, or excited about something. those who are stoked all of the time ...
 
#14
I love catching the "stoked" trout too Ira!

"stoked" is to be completely and intensely enthusiastic, exhilirated, or excited about something. those who are stoked all of the time ...
I was hoping no one had caught that yet. But in Ira’s defense, the ones in Pass tend to be stoked even in warmer weather, so I’m sure he meant to say that...after all he’s a teacher! :D
 

Rob Allen

Active Member
#15
I have mixed views on this.

1. I don't think people should be fishing for trout in warm water and that temp is somewhere close to 70 degrees.

2. Am am incredibly sick of the type community fly fishing has become everyone telling everyone else what to do. No hero shots , keep em wet, and on and on and on.
Everything you do, if you share it here you get jumped on for something. No more rules formal or informal go fishing and leave everyone else alone.
 

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