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Thursday, August 2, 2012

Water Temps and Trout Safety in the Summer

The blitz of early summer hatches is finally slowing down.  Still a few caddis out in the evenings and some giant nocturnal goldens, but the main attraction that is post-runoff fishing in Montana is on its way out for another year.  It always seems longer than a few weeks when you think about it in January!  Now it's T&T time!  Tricos and terrestrials!

Hoppers are clicking around on the banks, spruce moths are taking their morning dip, and the trout are keying in, but action slows big time in the heat.  Now that the snow melt faucet has been turned to the off position, water temps are getting into the danger range in mid to late afternoon.  This is the time of year you want to get up early and get off the water early too.

Zach Scott from FCFT with an early morning reward on the Blackfoot.  We put in at 7am.  On our day off.  Hardcore!

In case you are curious, here's your water temperature and trout lesson for this year.  Trout are a cold blooded, cold water fish.  This means that their body temperature depends on the surrounding water temperature, unlike we mammals.  As you also might remember from freshman biology, all animals respire to stay alive.  This means they take in oxygen and expel carbon dioxide, and in the process they metabolize food for energy.  A trout's metabolism is in high gear when the water is between 55 and 65 degrees Fahrenheit.  As water warms, it holds less and less oxygen.  Once water temps get above 70 degrees, trout begin to have a tough time breathing even though their metabolism continues to increase.  Thus, two things occur.  First, trout have a hard time keeping up with high water temps metabolically.  They just can't eat enough to keep up.  Second, when a trout is caught, it can't process enough oxygen and it gets a lactic acid build up in its muscles very quickly, just like an athlete.  If the fish is fought too hard in warm water, and especially if it isn't well revived, it will likely die from the experience even if you let it go. 

That's the main gist, but their are some other things to consider, as well.  First, some trout become better conditioned to high water temps and low oxygen levels if they deal with them frequently.  For example, fish in the lower Clark Fork might respond to these conditions better than fish in the middle reach of the Blackfoot.  Second, riffles and rapids increase dissolved oxygen in the water, so fish are usually more active in the riffles and the pools below them when water warms up.  Third, some species are more tolerant of warmer water than others.  Generally, cutthroat, bull and brook trout need colder water than rainbow and brown trout.  Add all this up and you can have better fishing and be nicer to the trout by following a few simple rules.  Here are a few tips to make sure you and the trout stay happy until we get some cooler temperatures.

1) Get a stream thermometer and use it

Joe Humphreys, one of my east coast mentors, calls a stream thermometer a fly fisherman's geiger counter.  I take water temps all the time when I'm fishing.  Sometimes, I just tie a piece of heavy tippet to the thing and hang it right off the boat.  The other day on the Blackfoot, when the water hit 65 between 10am and 12pm, the fish went crazy.  Then it hit 67, and the fishing shut down hard.  By using your thermometer, you can not only predict the feeding period, you can find spring holes and other little refuges too.

2) Pay attention to cold tributaries, springs, and the riffles

These sources of colder or more oxygenated water will hold more active trout then the big, slow, pools when water warms.  You have to be sneaky to find some of these spots though.  Always good to pay attention to cold spots in the water when you are out tubing with your friends.  Also, in winter you can spot springs because they'll steam on cold days.

3) Fish early

In Montana, we get peak sun in late afternoon, instead of midday like other areas of the country.  This means that sometimes peak water temps don't arrive until late evening or even later.  By morning the water has cooled down and this is often the best time to fish.  By 3pm, the water is too warm.  Go swimming instead. 

4) Fight fish quickly and revive and release them properly

While it is trico season, please be respectful to trout and don't take 20 minutes to land a big fish on 7x.  You will likely kill it.  This time of year, you should try to land the fish as quickly as possible.   Use a rubber net to land the fish and make sure it stays in the water, not in the air where it can't breathe.  Keep pics and handling to a minimum.  Before you release the fish, hold them in the net, upright, facing into the current, so that water is flowing over their gills.  When they're ready, they will usually swim out of the net on their own power.  Never release a fish before it is revived.  It won't make it.

5) Hit the small streams

Not as many big fish, but the water usually stays cold all day, and every once in a while you get a nice hog seeking refuge from the warm river water in the main stem.

Hope these tips help!  I'm hitting the Bob for a week, then Michigan for 2 weeks.  Till I get back, be nice to the trouts!  I should have some great pics to come.

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