Sunday, May 5, 2013

Colorado River: State Bridge and Radium

     We spent four more days last week electrofishing two more stations on the Colorado - a never-before surveyed reach at State Bridge, and at Radium. It was a wonderful week, although a little on the chilly side at times.
     Surveying a new station for which we have no fish population data at all is always a very exciting prospect. The State Bridge reach lived up to the anticipation. We chose to survey the two miles of river which starts right at the highway bridge. Out of all four of these river reaches, this section had the most evenly split population of sport fish, between browns, rainbows and whitefish. As a bonus there were some native suckers present as well - both flannelmouth and blueheads. 
     The rainbows were of course nowhere near as numerous as the browns, but this reach contained by far the most wild rainbows of any of the four reaches. This was something I didn't necessarily expect. They were definitely wild - clean fins, no telltale signs of hatchery origin at all. Besides, we don't stock any rainbows for many river miles upstream or down from this location. 
     I've often thought that in the spring, it seems like a common pattern for trout to feed aggressively as a storm front approaches and the barometer drops. Then, immediately after a storm passes through, activity slows significantly for a day or two. You can tell me if you agree with that or not. But for whatever reason, when we made our recapture run on May 1 at State Bridge, the browns were absolutely stuffed to the gills. They had clearly been on a massive feeding binge the day before, or possibly overnight. We also saw this the next day on the Radium reach. Food items appeared to be almost exclusively Pteronarcys nymphs. Just a little belly massage produced regurgitations of large volumes of orange goo - the very same orange goo that you see if you pull a Pteronarcys nymph apart. One interesting thing about this is that the feeding frenzy appeared to have taken place at a time when the water clarity was very poor as a result of low-elevation runoff.
     The highlight of my day on the 1st was being able to photo-document (thanks again to Mike Kline) a couple other prey items. Check out the pictures below. 
There's a little surprise in there - is that what I think it is??
Here it comes . . . wait for it . . . 
     I was just mentioning to you guys how little information I have on browns directly feeding on sculpin, and how most of the evidence I have is indirect. I would consider this to be as direct as you can get. Made my day. I was surprised to see that this guy had been eaten tail first.
 This one is an age-1 whitefish. He was eaten tail-first too. 

      This week, we'll be pioneering another new station: raft electrofishing the entire Paul Gilbert and Lone Buck reach in one shot. We've always surveyed those reaches in September when flows are really low, but I've been wanting to do it in the spring when there is enough water to float the boat. That way, we get a full population estimate of the entire reach from the Byers Canyon bridge to the downstream end of Lone Buck. We'll also be able to get an idea of whether or not any of our Hofers are spawning this year. I think there's just enough water right now, so we're giving it a shot Monday and Wednesday. Tuesday will be dedicated to Wolford - putting pike traps out and floating our new-and-improved merwin trap for the first time. I had a local welder (who has a great head for design) build one up over the winter, with a lot of design improvements over our original one that we used to take kokanee spawn last year. Thursday, I'll be taking some Summit County high school biology students (in Jamie Lambrecht's stream ecology class) on a field trip to do some electrofishing surveys in the Williams Fork tailwater.


1 comment:

  1. Jon, great timing on the photographic evidence of sculpin in the brown trout's diet! And thanks for all the great information.