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How can you tell if the water temperature is ok fish?

Summer fly fishing

Summer fly fishing is honestly my favorite time of year to fish here in Arkansas, especially since I am an avid wet wader. Our Arkansas summer weather last longer than northern states as with most southern states.  So even though we get to enjoy the season longer we still have to pay close attention to the water temps and what they mean in terms of trout survival.

Most states do not experience much rainfall during summer months so that typically means lower lake and river levels which results in higher and more lethal water temps for our beloved trout.  Let me break it down, warmer water contains less oxygen than colder water.

"So as the temperature rises and dissolved oxygen decreases the trout begin to stress."

That stress sets in well before lethal temps occur. Yep, this means that even though you may be a catch and release fisherman that if the temp is high enough, they could still die with you good intentions.

This past summer my fiancé and I took a vacation to Colorado, first fishing in a cold alpine lake and then we traveled south to the eagle river in Vail for some more trout fishing. We were amazed at the temperature increase in both the air and water. We made a decision to travel back north to another alpine lake so we wouldn’t risk stressing and killing trout in the eagle river.

How can you tell if the water is safe or not?

So, you may be curious, how can you tell if the water is safe or not?  One way is the more obvious approach, if you are sweating in a t shirt and shorts then it may be too hot. Or, if you spot trout in the water opening and closing their mouths you may think that they are feeding. Nope. They are trying to circulate water around their gills for more oxygen. That rapid opening and closing of their mouths is almost like they are gasping for air.

Another way to tell if the water is too hot for the trout is a stream thermometer.  This is the more scientific and precise route.

"What’s great is that stream thermometers are affordable ranging from $14 at Walmart and up to $40 online at Amazon. " 

So now let’s go over the different ranges of temperatures and tolerance for the different species.

Brook trout need more oxygen

Brook trout need more oxygen (lower water temperatures) than brown trout and rainbow trout.  Brook are more common at high elevations because of this.  The best feeding (catching) temperature for brooks is about 44-64 degrees.  Above 65 degrees brook stress and then past 70 degrees is lethal. 

Cutthroat like the Brook trout thrive much better in colder higher elevations.  Cutthroat optimal feeding (again, catching) temperature is lower than the brook at 39-59 degrees.  Which means cutthroat stress point is about 60 degrees and the lethal point is around 68 degrees.

"Cutthroat trout are the more sensitive to the water temperatures than the other species."

Brown and Rainbow trout are the hardiest of all the species which may explain why they are so common in southern states and have higher survival temperature ranges than the brooks and cutthroats.  Brown and rainbow feeding temperature is 44-67 while 68 stresses them and the 75-77 degree range is lethal.

This information now allows us to take action

I know, I didn’t realize that the water temperature mattered so much in terms of them surviving even though I do my best to “let them breathe” and “keep them wet”.  This information now allows us to take action and be responsible fisherman in warmer temps and luckily, we don’t have to stop fishing all together, just go earlier and later in the day.

That for me is simple and easy enough if it ensures that the trout may continue to thrive and grow so that we can enjoy catching and releasing them years to come.

Comment below what your thoughts are on this.

Tight lines and good vibes y’all!

Rebecca Lentz

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