leaping fish

Question
Hi Pat -

We live on the E. fork of the Satsop River in Grays Harbor/Mason county.  The salmon season is always exciting.  It's fun to watch the fish run up the river in droves (schools, I guess) every year, and the spawning that goes on out in front of our house.

For the past few weeks, there are a few salmon (King?  Steelhead? the chum run is about finished...) spawning out in front of our place that leap wildly out of the river, twisting in the air, somersaulting, and slapping back into the water.  They'll do this 4 and 5 times in a row, then disappear for awhile, then do it again.  

Why do they do this?  We've lived here for 4 years, and haven't noticed much of this behavior before.

Thanks for any light you can shed on our curiosity.

Lee Anne

Answer
All ocean-going fish are prone to picking up a parasite commonly known as sea lice. I've caught salmon and steelhead and found them affixed to gills and around fins. One way a fish with lice will try to dislodge them is to rub against bottom rocks and leap out of the water.