Warm water killing fish?

[Hammer Handle]

With little rain and hot weather, the lakes seem to be warmer than ever. A lot of lakes have 80 degree water at the surface.

With this, I have noticed many dead fish. Most are walleyes.

Is this due to the stress when they are caught and released in this warm weather?

I caught a wallyeye in 25 feet of water this last weekend. I unhooked and released it right away. I caught a second, and saw the first one floating. As I let the second go and picked up the first too keep...the second was floating.

I was just out fishing for "fun" as I have fish in my freezer. But, decided to keep these too and quit for the day. No, this lake had no slot limits.

[Scott M]

I've been wondering this too. The access ramps are like stepping into a jacuzzi.

The good news is that by this time there is plenty of forage so finding fish that are at high risk to hooking mortality (i.e. walleye) and getting them to bite is tougher. It's the dog days of summer for a tough bite and hot weather.

If fish can find cooler water, no problem...but on shallow lakes and rivers, you will see some summerkill, not from heat but from lack of oxygen. Hot water can't hold oxygen like cold water can.

The other concern about lakes heating up lately is the lack of growth. When water is this warm fish bioenergetics are inefficient. Metabolism is so high whatever they are eating gets burned off. So you see two periods with little or no growth: midsummer and winter. Not good if you want to catch trophies or lots of eaters.

[BobT]

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Hot water can't hold oxygen like cold water can.

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I wonder if you've answered the question. You catch a fish in the cool deep water (25') and bring it up to the surface. It has just been put through a workout so it is in need of more oxygen. Similar to use breathing heavier they too need more. Then you release the fish into water containing low oxygen levels not to mention being removed from its environment into a deadly atmosphere.

Maybe an aerator would be beneficial in this situation?

Bob

[Black_Bay]

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Quote:

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Hot water can't hold oxygen like cold water can.

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I wonder if you've answered the question. You catch a fish in the cool deep water (25') and bring it up to the surface. It has just been put through a workout so it is in need of more oxygen. Similar to use breathing heavier they too need more. Then you release the fish into water containing low oxygen levels not to mention being removed from its environment into a deadly atmosphere.

Maybe an aerator would be beneficial in this situation?

Bob

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Actually the surface water still has plenty of oxygen even at these warmer temps. It's getting continually mixed by the wind. The problem is the thermal shock of coming from say temps in the high 60's at 25 feet to 80+ degrees at the surface.

[Scott K]

You may have put the fish through to much, pulling them out of the cool 25' water into the hot 80 water at the surface, this isnt to uncomon in middle of the summer, mostly in deeper water though!

[Surface Tension]

I was in tourney last weekend and heres what I observed.

Surface temps in the low 80's. That same temp reached down to 20' of water. For someone that is anal about temps(me), I don't find warm water temps driven down that deep too often.

We boated a 5lb.2 and a 4lb eye. I know for a fact my livewell was well oxygenated, of coarse it was at surface temp of 80 degrees, same temp as the bottom. At 20' is were the temp break started.

Heres the kicker, large eyes lay on the bottom, like a dog on a hot day, the bottom temp is constant. Cooler then the water surrounding itself, eyes regulate their internal temps by laying belly on the bottom. Normally they can leave that bottom and feed when the opportunity arises, but not for long and on their own terms. Take them out of that bottom(core) temp and they go into shock. Get them out of +20' of water and lack of being able to expel air in their air balder + leaving the bottom hugging temps means lots of stress. A very quick release sending them down head first quickly is what you need. Thats extra boost pushes water through their gills and instinctively gets them back on the bottom.

Having said that I'm dammed for killing two large eyes.

I knew better then to put them in a livewell under those circumstances to get to a weigh-in.

Anyway, I hope this sheds some light on warm water mortality.

[Ufatz]

Us old time trout fisherman know that there is a time when you just don't fish. Check around the west and you'll find many areas where even the guides/outfitters more or less hang it up for a while.

But of course that wouldn't slow down the tournament anglers I guess.