The Skwala Hatch on the Bitterroot River

Now, before you get too excited and start making travel arrangements, the Skwala's aren't out yet.  As a matter of fact we have a fresh two inches of snow on the ground.  However, the time is nearing and I wanted to talk about what to look for and expect during the hatch.  Skwala nymphs, like most stonefly nymphs, live in the middle of the river for almost an entire year.  The nymph is classified as a "clinger", meaning they attach themselves to the rocks. They aren’t good swimmers.  Stonefly nymphs, as a whole, are very susceptible to variations in water conditions, their diet is mostly comprised of algae and diatoms and they require clean, cold and highly oxygenated water.  They can be the proverbial canary in a coal mine for a river.

Skwala nymph photo taken on February 10, 2011

In late winter/early spring Skwala nymphs start their behavioral drift, which is exhibited by most hatching aquatic insects.  Typically, there is an environmental trigger that cues an nymph to start emerging; either light cycles, or water temperatures.  In the case of the Skwala, it’s when day and night start approaching a 12/12 cycle.  When this occurs, the nymphs start their migration to shore in mass.  The behavioral drift ensures the survival of the species.  If only a few nymphs migrated at a time, they would be easy prey for fish.  However, when millions of nymphs are migrating at once throughout the river, i.e. behavioral drift, the fish can't get them all.  This is happening right now on the Bitterroot River.  I usually start seeing Skwala nymphs in the rocks around the first week of February and this year is no different.  The nymphs will congregate close to shore and stack into the rocks until the next environmental trigger.

That next trigger will be water temperature, not light.  The magic number is 42º.  Skwala adults will start to emerge when the water temperature reaches 40º, but they really get going at 42º.  If you don't carry a thermometer, you may want to seriously reconsider.  I carry one on the boat and ALWAYS have it in the water.  Water temps can tell you a lot about fish and insect behavior.  Once I start seeing water temps creeping into the 40's, I will start throwing Skwala dries, even if I don't see adults.  

Adult female Skwala taken March 2010

An important side note of the Skwala hatch is you will not see the adults in mass.  The female stonefly is the only one to develop wings, however most female Skwala don't fly.  If you look closely you’ll see that some have underdeveloped, almost mutated looking wings.  Most people I have talked to claim it’s because the Skwala has evolved to emerge when the air temps are quite cool.  Instead of flying over the river and dropping their eggs, Skwala females deposit their eggs by crawling back from the bank.  Note that even the most observant angler will have a hard time seeing adult Skwala's.  On a good day, when the hatch is in full swing, I usually see a  dozen at most.  However, if you have a thermometer, you will be way ahead of the game.

Nice rainbow taken on a Skwala dry March 2010

The Skwala hatch is no longer a secret on the Bitterroot River.  In just the short 11 years that I have been fishing here, the pressure has measurably increased.  As a matter of fact, it was the Skwala hatch that originally brought me to the Bitterroot.  And why not?  During this time of year anglers in other parts of the country have to fish with size 20-24 midges (if they aren’t forced to nymph), while we throw size 8-10 dries!  Because of this, don't think you’re going to have the river to yourself.  I’m not talking Madison, Big Hole or Bighorn  crowds but 6 or more boats in one section is common.  Be patient.  There is plenty of water out there and everyone is entitled to fish, good etiquette goes a long way.  Common courtesy give’s wade fishermen a wide berth and when close to  another boat, pull over to put some distance between you.  No one likes the feeling of being crowded.  That said, the Skwala hatch on the Bitterroot River can offer some of the best fishing of the year.  Forty fish days are not rare and some of the biggest fish of the year can be caught on dry flies.  The fish are just coming out of winter, are very hungry and are greeted by a steak sized bug floating down the river.  This year is shaping up to be another great one. Have fun and come by the shop and show me pictures of the one that didn't get away!