Sunday, January 27, 2013

The Merwin Trap

     For kokanee spawn this year, we tried out a new piece of gear called a Merwin trap that has never been used in the state before. The idea to use one of these came from some of my southern counterparts, in particular Jim White in Durango. New Mexico uses a couple of these for both walleye and kokanee spawn operations. Jim found out about New Mexico's use of this piece of gear and thought that it would work great for some of our applications, particularly capturing the developing kokanee broodstock at the new Lake Nighthorse. Mike Martinez, a technician at the Durango hatchery, welded it up. The Lake Nighthorse fish aren't mature yet, so there wasn't any need for the trap yet in 2012 down there. So, I got to be the lucky guy to deploy this thing for the first time at Wolford Reservoir, where we knew we were going to have a good kokanee spawn season. 
     Here we are trying to figure out how to put the thing together:

     There is always a lot of kokanee activity right around the boat ramp, so we kept things simple with this first try and set it right there, using the dock to tie off to. In the photo below we are getting the lead figured out. It's ten feet tall, with a float line on top (you can see the white floats) and a weighted line on the bottom. The lead is 150' long, but we didn't use the whole length of it.

      Here it is, deployed and anchored. There are two pots with throats in them, so when fish that are swimming parallel to shore hit the lead, they turn out toward the lake to get around it. They are forced to swim into the pots and are not able to find their way back out. It's just like a huge minnow trap.

     This is what it looked like from above. Strong winds could be tough on this thing, so it was great to have a relatively sheltered spot.

     I had no idea what we were going to find after this thing fished for a night. I half-expected that there would be no fish at all in it. However, the picture below shows what was waiting for us the next day

     This was a very good sign. The best-case scenario in my mind is that we could potentially take as many as 2 million eggs out of this thing if everything went well. We took 1.9 million over the course of a few weeks. It was a spectacular success. This completely made up for the fact that the Williams Fork egg take was a bust this year, and it even covered a little bit for Granby's weak showing. Here we are picking up one of the pots on one of the spawn mornings (below).

     Check out this splake that showed up in the trap (below). We had a few show up, which surprised me. We haven't stocked them since 2000.

      Since this was the first time any of us had used one of these, we quickly figured out some things that we would design differently, and I'm already having a second one built. This might have great usefulness during Walleye spawn, and my friends in the Southeast region are going to try it at Pueblo in the spring. I can't wait to see how that works. 
     As far as using it next year for kokanee, I just have my fingers crossed that we still have kokanee living in either Wolford or Williams Fork next fall. Things are not looking good at all for those two lakes unless our weather pattern changes drastically.

On another note, I've got a new report on our website about the Colorado River, Pumphouse-Radium. Take a look if you're interested and let me know your thoughts, thanks!


  1. John, we tried traps nets for walleye and caught a ton. The only problem was 95% of the walleye were males.

  2. Yeah, Mandy was telling me the same thing. But when I worked for KS and helped run walleye spawn there, all we used was trap nets - a dozen of them spaced across the face of the dam. So we'll see. If it's a benefit then great, but if not, no big deal. Might as well give it a shot.

  3. You are welcome to come to New Mexico and see it in action. Call the Los Ojos Hatchery.