Saturday, September 28, 2013

Used and abused

     Hi folks, and sorry for the long break. Summer just becomes a wave of activity that builds and builds and doesn't really crest until kokanee spawn is over with. I have every intention of continuing this blog; there just hasn't been time over the summer.
     I had a great summer, but it ended too soon as always. Every summer I wish I made it to more high lakes, although I did squeeze in one last pack trip at the end of August. 
     We ran our annual population survey of the Blue tailwater below Dillon on Friday the 16th and Monday the 19th of August. It's two days of work because we use a mark-recapture survey. I like surveying this section during the second half of August because I feel that we're getting a relatively clear picture of the resident fish population. If we wait until September or October, it's always hard to know how much the data is influenced by seasonal movements of browns getting ready to spawn. And when you're working on a section of river immediately below a dam, if there's a seasonal upstream concentration of adult browns, then all your data will really tell you is that the browns are getting ready to spawn.
     In higher-water years, if there is at least 150 CFS coming out of the dam after August 15, we put the electrofishing raft on the river and run the survey starting at the power plant bridge and end it at 7-Eleven, which is 0.7 mile. If it's a low-water year, such as 2012 and 2013, we wade electrofish a smaller reach, starting at the USGS gauge and working upstream to the power plant bridge. So, the low-water station is a portion of the high-water station. 
     This summer was a weird time for the Blue tailwater, because releases were pegged at minimum flows for a very long time. For August, 58 CFS is about half of the 25th percentile of flow. On December 10, 2011, flows dropped to near the minimum release of 50 CFS and stayed there until just the past couple of weeks. There had been brief periods of marginally higher releases, but the river never exceeded 200 CFS during that time, and in 2012 and 2013 there were no flows that ever resembled a "runoff" period. The last time the river exceeded 200 CFS was August 15, 2011.
     I want to be clear up front here and point out that I'm not trying to run down the Blue tailwater or be insulting. It gets a huge amount of fishing pressure and generates a lot of economic activity. It is the most accessible, visible, and urban of all our gold-medal trout rivers. But during such a long period of constant flow, the Blue tailwater resembles an aquarium more than any river I've ever spent time on. We know that the forage base is very sparse, and my belief (I don't have solid data to back this up, but we're moving in the direction of doing a study on this) is that at those low flows there are very few mysis - maybe even none - getting entrained in the tailrace. It's also really cold during the growing season. So between the cold temperatures, lack of food, and insanely high fishing pressure, growth rates in the fish are extremely slow. I stock brood culls from the Glenwood Springs hatchery there, and unfortunately that's really the only thing that maintains a large-fish component to the fishery there. 
     During this year's survey, I thought the rainbows were in particularly rough shape. So much so, that on the recapture day I designated an official photographer to document the condition of the fish. So here's a "rogues' gallery" of rainbows from the blue. I'm dead serious when I say that these fish have it pretty rough. Be sure to click on the pictures themselves so you can see close up the full gnarliness of the situation.






     There is literally not a single fish in that reach with a clean jaw. The other thing going on, that I hadn't really seen before, is shown in the pictures below. Massive abrasion starting from the upper jaw and sometimes extending all the way back nearly to the dorsal fin. I really have no idea what causes this. It's only on the brood cull rainbows, and not at all on the browns. The only thing I can think of, is that they have such a hard time finding anything to eat, that they're rolling rocks looking for food, causing the abrasions. Maybe that's a stretch, but it really baffles me. I'd  be interested in hearing anyone else's ideas.





11 comments:

  1. I personally haven't thought of the Blue as Gold Medal water for a long time. I know that Silverthorne/Summit County would fight it, but maybe it's time to delist the Blue as Gold Medal water and just make it a put and take fishery.On this stretch of water C&R looks like cruel and unusual punishment to me.

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  2. What happened to all the fish that have the ID tags? I see a couple tags in the pictures above, but how many are being re-captured? How's their growth? Why are you stocking every year if these fish supposed to be able to survive? Where are they going? What are your plans for this river? Obviously the fish aren't dealing with the fishing pressure and availability of food stuff well.

    I think the abrasions are from the fish trying to hide from fisherman. You can see them stacked up under trees and undercut banks and at this low water, they are all trying to stay out of the reach of fisherman. That, and all the abuse they receive from people handling them poorly.

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    1. Andrew, all your questions have complex answers. I've been tagging the fish that I stock in order to track growth, weight gain/loss, etc. as a way to get more specific details about how they fare after being stocked. I haven't worked up any of this data yet, but you can see last year's report here:
      http://wildlife.state.co.us/SiteCollectionDocuments/DOW/Fishing/FisheryWaterSummaries/Summaries/Northwest/BlueRiverinSilverthorne.pdf

      By reading that report you can see what I'm doing with the tag information.

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    2. After I process this year's data, we can discuss your other questions further.

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  3. Woo-hoo! You're back. Thanks for the write up. Do you see the management plan changing in light of your obervations?

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  4. I too think they get like that from trying to dislodge hooks on the stream bed or stuffing their heads under rocks. I don't give trout a lot of credit for abstract thinking, and the idea that a number of them have independently arrived at the same conclusion (ie, that you can root under the substrate like an armadillo and turn up food-stuffs) is a little far out for me.

    I have quit fishing that stretch. It is cruel to catch those fish. That place is a joke.

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  5. That is some gruesome work.

    "The last time the river exceeded 200 CFS was August 15, 2011."

    That right there is all you need to know. It's just a poor trout habitat.

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  6. These fish jump/ breach when on the line and take many headers into the rocks and gravel in the shallow pools caused by the low flows. I've also noticed these fish don't spook like other low-flow/ high-pressured trout.

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    1. So, you think the abrasions are happening at the time the fish are being caught? I think that's the best explanation I've heard so far, because it explains why the browns do not have it. These fish get caught many more times than the browns do. These fish don't spook because they spent the first 5 years of their lives living in the raceway at Glenwood, being fed.

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    2. The brood culls are probably banging their heads on everything in the river looking for pellets to eat.

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