Heat kills - any anecdotal evidence?

There is a small lake at about 2700' on the west side of the Cascades not too far from Pugetopolis that I like to fish every year a few times. It gets a modest plant of cutthroat fry every couple of years and there usually are plenty of healthy 12-14" fish. In my experience, it peaks around 4th of July with a great Callibaetis hatch, which coincides with when the Snoqualmie Tree Farm is closed, so I usually fish it this weekend every year.

I went up on Friday to avoid the holiday weekend traffic (the lake is never crowded, but the roads getting there are). I got on the water a little after 11. It had rained up there over night and was cloudy all day; the air was cool, about 66ºF. However, the water temp was warm, 74ºF and the cooler air meant that fog was swirling over the lake. I looked forward to some good fishing. There were a couple species of caddis, Callibaetis mayflies, and midges over the water, but no sign of fish. I started fishing with a wet fly, but the lake was dead. After about an hour of fruitless casting, I discovered that “dead” was not just a euphemism. I encountered one fish belly up near the far end, towards which a light wind was blowing, and thought at first maybe a mishandled C&R, but then I saw another nearby. At that point, I reeled in my fly and kicked along the far shore of the lake, counting 15 dead fish along the way. Given the cooler overnight temps the past few days and the rain Thursday night, I suspect the water temperature was quite a lot warmer earlier in the week. I imagine dead fish are scavenged pretty quickly by osprey and raccoons, or will sink to the bottom once they reach a certain stage of decay, so seeing 15 dead fish 4 days after the peak of the hot weather, seemed to me to mean that a lot more had died, but were not in evidence. I spent about 2 hours or more on the lake and at the launch (where I took this picture of another dead 14-15" fish) and came away with the distinct impression that the fish kill may have been close to 100%. Very sad. It is stocked every couple of years, but it may be a few years before it fishes well again. Maybe there are still fish hanging out deep, but I tried fishing a weighted fly on a long leader and didn’t touch any fish.

Have any of you seen any evidence that the recent extreme heat event led to fish kills in any lakes or streams you have visited this week? I would be curious to hear if this is a one-off or was more common.
dead fish Lake Evan.jpg
 

Jim Ficklin

Genuine Montana Fossil
Sorry to hear that, Richard. I'm no fisheries expert, but I did a Google search and discovered this info. Seems plausible to me. Cutties & Brooks seem to be the most sensitive to elevated water temps. People & fish both took a beating during the recent heat wave & I fear more may be yet to come.

 

girlfisher

Active Member
Depth and altitude play a role for sure. One of my favorite lakes lies at about 3700 feet but is only about 20 ft deep. It suffers from summer kill quite often and this year will no doubt be one of the worse!
 

Squamishpoacher

Active Member
Depth is the most critical. We were at lakes over 4000 feet last week that at the surface the temperature was exceeding 70 degrees. The fish were all showing at the bottom below 35 to 60 feet. They will avoid warm water near the surface as it has low oxygen and they will go to depths where its cooler. The snow melt in high elevation areas has been very rapid the past week. Lakes at higher elevation receive some benefit from cold water input from snow melt but it is short lived. Extensive periods of temperature over 68 starts to become lethal in most salmonids. That lethal threat becomes more acute as temperature rise over 70 degrees. Catch and release in these temperatures only adds a stressor that is not healthy for them. Hopefully we begin seeing a cooling trend accompanied by some moisture, and without lightening accompanying it.
 

Grayone

Fishin' to the end, Oc.P
WFF Supporter
There is a small lake at about 2700' on the west side of the Cascades not too far from Pugetopolis that I like to fish every year a few times. It gets a modest plant of cutthroat fry every couple of years and there usually are plenty of healthy 12-14" fish. In my experience, it peaks around 4th of July with a great Callibaetis hatch, which coincides with when the Snoqualmie Tree Farm is closed, so I usually fish it this weekend every year.

I went up on Friday to avoid the holiday weekend traffic (the lake is never crowded, but the roads getting there are). I got on the water a little after 11. It had rained up there over night and was cloudy all day; the air was cool, about 66ºF. However, the water temp was warm, 74ºF and the cooler air meant that fog was swirling over the lake. I looked forward to some good fishing. There were a couple species of caddis, Callibaetis mayflies, and midges over the water, but no sign of fish. I started fishing with a wet fly, but the lake was dead. After about an hour of fruitless casting, I discovered that “dead” was not just a euphemism. I encountered one fish belly up near the far end, towards which a light wind was blowing, and thought at first maybe a mishandled C&R, but then I saw another nearby. At that point, I reeled in my fly and kicked along the far shore of the lake, counting 15 dead fish along the way. Given the cooler overnight temps the past few days and the rain Thursday night, I suspect the water temperature was quite a lot warmer earlier in the week. I imagine dead fish are scavenged pretty quickly by osprey and raccoons, or will sink to the bottom once they reach a certain stage of decay, so seeing 15 dead fish 4 days after the peak of the hot weather, seemed to me to mean that a lot more had died, but were not in evidence. I spent about 2 hours or more on the lake and at the launch (where I took this picture of another dead 14-15" fish) and came away with the distinct impression that the fish kill may have been close to 100%. Very sad. It is stocked every couple of years, but it may be a few years before it fishes well again. Maybe there are still fish hanging out deep, but I tried fishing a weighted fly on a long leader and didn’t touch any fish.

Have any of you seen any evidence that the recent extreme heat event led to fish kills in any lakes or streams you have visited this week? I would be curious to hear if this is a one-off or was more common.
View attachment 287508
Yes. In my pond/lake. Trout do not get enough oxygen at 74 or higher temperatures. I am in the process of losing fish as you read this. My waterbody is only 12 feet deep so I see this happen all to often. This is an over simplified explanation.
 

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