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.

Summer break

     We finished up Granby last week and got started on Green Mountain. At Granby we ended up capturing exactly 200 lakers in our 32 net sets, for an average of 6.25 fish per net. That falls right in there with the past couple years. We did have one net though, where we picked up NINE fish over 30". We've never seen that while we've been using this sampling scheme. It was astounding. We just happened to hit a big group of them travelling together, I guess. Any other time we pick up big fish, they're by themselves, or maybe there are two of them. Never nine of them.
     This is our third year of running the six-hour gillnet sets at Green Mountain. We set a new single-net record on Thursday with 18 lakers in one net. The previous record was 9 fish. We also picked up a 14- and an 18-pounder.
     Another day on Green Mountain tomorrow, and then I'm going to be off for the rest of the week, camping with family visiting from out of state. Hope you're enjoying this warm weather as much as I am.
     James W - those are great questions and I'll get into them soon. I never know how much people are interested in the hardcore analytical side of things but I love discussing it, so stand by on that.

Granby spring netting

     We've been running our gillnet surveys on Granby. I've got a sampling scheme set up where I set gillnets (150 feet long, six feet tall) in 32 random locations all over the lake for six hours each. We typically set 8 of these per day, so it's four days of work on Granby. We got two of those days done this week, Tuesday and Wednesday, and then we had a couple days of horrendous wind. So we were sidelined Thursday and Friday. We'll be out there again tomorrow and Tuesday to finish it off.
     The idea behind running 32, 6-hour net sets in random locations was something that I started working on a few years ago. The traditional way to sample our reservoirs is with overnight gillnet sets, in which the nets are always set on shore, extending out into the lake, perpendicular to the shoreline. If my goal is to know what the trend in the lake trout population is, and have a good amount of statistical confidence in the data, setting a small number of shoreline gillnets (like 6 of them) overnight does not do a good job answering that question. Now, I have a set of 32 independent samples that tell me a lot more about the lake trout population. There are a lot of different statistics that I get out of this sample design, but the one that should tell us the most about trends in lake trout density is the average number of lake trout captured per net.
     This is only the third year that I've sampled the lake in this way. In 2011, the average lake trout catch was 6.4. In 2012, it was 5.3. Right now, with only half the netting done, it's 7.5. We don't have a way to directly measure the actual number of lake trout in the lake, but 5 or 10 years from now, if the average catch is twice, or half, what it is now, we can safely assume that the density of lake trout in the lake has either doubled or declined by half (with a certain degree of error in these estimates, of course).
     I keep using the word "density" for a reason. Even if I run this survey at the same time every year - or at the same water temperature - the biggest variable that I have no control over is the volume of the reservoir. So, for instance, this year on our first day the water was at 8233', which is 30 feet lower than it was when we did this in 2012. So even though I'm setting nets in the same locations (mostly - some of my locations are out of the water and so I have to use alternate ones), those locations are all 30' shallower than a year ago. So it changes the distribution of the fish, but it also changes the density. If you have the same number of fish and put them in a smaller volume of water, the catch rate should go up even though the number of fish is the same - because the density of fish is higher. So, when I get into the analysis of this data later on, I'm going to experiment with correcting for reservoir volume at the time of the netting, and see if that yields numbers that make sense.
    So here are a few photos, courtesy of Mike Kline. Here's the biggest fish we've picked up so far, weighing in at 20.5 pounds:

     This fish did have a fresh meal in its throat, so we investigated:

     It was a big white sucker. Interesting. Here is what we know about Granby right now: The prey base for large macs has become increasingly sparse the past couple years. The kokanee population has taken a huge dive, and we're not stocking as many rainbows as we used to. We know that suckers are definitely not the preferred food item for lake trout, but obviously if that's the only thing available to them, that's what they'll eat.

     I've been thinking a lot about body condition in these lakers. In every other fish population I deal with, when prey is scarce, you can see it very clearly in the body condition of the fish. For comparison, if you look at all the brown trout larger than 14" in a certain reach of the Colorado River, they tend to be all skinny or all fat. There's not that much variation in the body condition. What I'm seeing right now at Granby is that some of the lake trout look skinnier than any lake trout that I've handled to date. But some of them (like the one above) are in perfectly fine body condition. Here's a good example of one of the skinny ones we've seen:

     That is a very skinny lake trout. Nearly starving, I would even venture to say.  So I guess what I'm saying, is that under conditions of sparse forage, it appears to me that the variability of body condition in large lake trout in Granby increases. It seems that a portion of them successfully switch to other prey items, and some of them don't seem to do that at all. I don't know if that seems like a relevant, much less profound, conclusion or not, but I can say that this is not the way that any other trout population that I've seen behaves. It's fascinating, and I wish I knew what determined which fish are successful and which ones waste away. When I get the data worked up, we'll see if my hypothesis about increased variability holds true.

Stonefly heaven

     I don't have a lot to report on this week. I was on the river all day (for fun) and I'm somewhat fried now. The giant stones are popping on the Colorado. Such a wonderful thing to see. I went down and checked on Friday and didn't see a thing, but today they showed up. At Pumphouse they were still seeming a little groggy and unsure, and I suspect tomorrow will be the big day. It's uncanny how often they hit at Pumphouse right on Memorial Day weekend.
     This week we finished up pike trapping at Wolford and Green Mountain. Got 14 out of Green Mountain, none of which were smaller than about 24" - a good sign. At Wolford we ended up with about 66 fish, all but one of them from last year's spawn.
     We also ran our standard gillnet survey at Wolford this week. From that, and from the pike trapping, I've got a couple of observations on Wolford this spring. First, the kokanee are still looking excellent and we should see another great year for summer kokanee fishing once the water clears. Second, I have seen more large (20" and larger) brown trout in Wolford than I've seen in my time here. Should be a good year for large browns there also.
     I'm about to nod off. Please make comments and let me know what you want to hear about. Ron Fletcher - you had asked about Muddy Creek below Wolford. I'll just say this: It's a nice place. That is all.

Waiting for the reservoirs to fill

     We've been in a little bit of a holding pattern for the past week. It's time to start my annual spring reservoir netting surveys, but I decided to delay these a little bit in order to run the nets at a time when the reservoir elevations are at least a little closer to what they have been in the past. If the reservoir elevations are extremely different, it will be harder to draw solid conclusions when I compare this year's data with past years. But we'll get started this week, beginning with Wolford. We've been spending our time over the past week mostly running pike traps in Wolford and Green Mountain.

     So, I'll answer a few recent questions. From an anonymous poster on another website:

"Why can folks put feeders on the river in close proximatey (sic) to public waters?"

     Well, the real answer to this question is because it has never been outlawed. I can think of many reasons to do so. I personally don't agree with this practice at all. However, to propose such a regulation would invite a tussle of political maneuvering the likes of which I, as a lowly field biologist, have no desire to engage in. I could certainly provide some very solid arguments for why this practice is detrimental to the wildlife of this state in the big picture and the long run. But the impetus for passing such a regulation would have to come from an organized group of sportsmen from outside this agency. Unfortunately, our sportsmen are not all that organized, and at times that really costs the wildlife of this state. Not trying to be controversial or un-politically correct here, just calling it as I see it, personally.

 "Why then cannot I use corn or such to shoot deer or ducks over? "

     Because enough people thought it was unethical to do this, and passed regulations and/or statutes to outlaw this practice. But the analogy you're drawing here is more similar to chumming fish, which is also illegal. But where do you draw the line between feeding a free-ranging fish population in a river and chumming fish? Therein lies the rub.

"Are there the same 2 week regulations?" 

     I don't understand this question.

"Why is this allowed at all...shooting food into the river? Do they feed what they want? re they regulated as to what feed they can use?" 

     Again, it's allowed because it's never been disallowed. There are no regulations regarding what type of fish feed people can throw into a river. I'd be glad to discuss this topic further, if anyone is interested in doing so. Please comment.

Here's another:

"I read your comments abouth the Blue River in the Denver Post. You said the aquatic life in the river is just not up to supporting a quality fishery and that the lower section, down towards Green Mountain is especially barron. My observation of the Blue is that there are long sections of river that are just gravel and have no structure. I would think dumping a bunch of good sized rocks in those sections would increase insects and the fish they support. I see alot of the same featurelss water on the Platt downstream of Deckers. Are there any plans for streambed impovements on these rivers. It seems to me that improving what we already have access to is just as important as getting more access. "
     Thanks for the comment Homeboy. Please use your real name. This is a good question. I don't disagree that some of the sections of the Blue downstream from Silverthorne have poor habitat quality. I'm sure that those sections would benefit from habitat improvements, to a certain extent. I am not aware of any immediate plans to do habitat work on these sections, but it certainly may happen in the future.
     However, I don't believe that physical habitat quality is the limiting factor on the trout population on the Blue. I have lots of good data that shows that slow growth is a consistent trait of this trout population, in multiple locations on the river. Slow growth is not caused by a lack of physical structure. It's caused by a lack of food availability. You're suggesting that working on the physical habitat would increase insect densities. The focus of a physical habitat project in a river is to improve the trout habitat, not necessarily to improve insect production. Those are two different things. Cobble riffles are generally the best habitat for insect production (at least, the kind of insects that are desirable for trout and us), and I can show you plenty of featureless, cobble riffles on the Blue that are just fine insect habitat (but poor trout habitat). But, that doesn't change the fact that the insects are sparse there. What I'm getting at is that I think it's more of a nutrient/chemical issue of some kind than it is a physical habitat issue. 
     On the Colorado, there are many places where the trout habitat is awful- the river is far too wide for the amount of water in it and there are vast, featureless cobble riffles. There is a far higher density of both insects and trout - and far better growth rates in the trout, even though the habitat is very poor. It's an interesting comparison to the Blue.
     Another important thing to think about, is that there are some sections of the Blue - the one that comes to mind is the section from Boulder Creek down to Columbine Landing and the Highway 9 bridge - where there is no shortage of good, quality trout habitat. It's got plenty of deep runs and pools that are difficult to wade at any flow. There is a ton of large object cover. And the trout population there is really no better off than the population in the sections with poorer habitat. The density is a bit higher as a result of the better structure, but the quality of the trout themselves is no better. They still grow very slowly, and do not often reach very large sizes. 
     I'm not saying that there is no place for doing some in-channel work on certain sections of the Blue. I just think that if we do, we need to be very realistic about what the potential benefits of that work would be. It's not going to magically produce a high density of quality-sized trout. It would produce a higher density of skinny, 8-10-inch browns.
     I've had a lot of discussions with various folks about how we could go about directly addressing the productivity issue on the Blue, and we've got some ideas floating around. They're pretty preliminary though.

Now - I covered two specific topics in this post. Did I contradict myself between the two topics? You tell me.

Customer service

     Here are a couple emails (from the same person) which I received recently which really stood out from the crowd. They are all-time classics, so I thought I would share them here:

I'm a 11 year summit county local and would consider myself to flyfish far more than others. Far more. I know the Blue River system top to bottom and I have no clue as to why you would have a 2 fish limit below silverthorn to Green Mtn. There really aren't any fish there and the ones that are there can be big...why are you choosing to kill off this fishery in a drought year?  I haven't seen your latest shocking survey for this section but I can say from my experiences, this section, of almost 12-15 miles of river, is almost dead - in public water at least. Did you see the catch rates from the fly fishing championships last summer - it was horrible!

A 2 fish limit is completely unreasonable and tells me a little more about the mgt. I clearly remember the whirling disease / stocking program fiasco. Don't kill this resource for so many.

The second email:

I am looking for supporting documentation and an explanation to justify the 2 fish over 16inch limit on the Blue below silverthorne to Green Mountain. There are hardly any fish in this section of the river - and your management survey clearly shows that fish don't do well the farther downstream of the dam that you go. How can you possibly have a regulation like this in place? Licenses are never checked and bait containers are everywhere. All of this aside, how can you possibly justify a 2 fish regulation like this? My next correspondence, if I don't receive an

answer, is to the newpapers in Colorado. They would love to jump on this.    

     I have to admit, I was pretty stumped at first as to how to go about responding to these emails. I would love to have any of the readers of this blog put yourself in my shoes and let me know how you would respond if you were me.

     This past week, we did a few more days' work on the river, which will pretty much conclude our mainstem river work for the spring. This week we'll be getting the gillnets out and switching to lake/reservoir mode. On Monday and Wednesday, we did something that hasn't been done for a long time: we ran a spring raft electrofishing survey of the Paul Gilbert and Lone Buck units, right below our office. There was just barely enough water to float my 14-foot electrofishing raft, so we went for it. The results were very encouraging.
     The reason I decided to run this survey was mainly to see what kind of numbers of rainbows are showing up to spawn, with the success of the HXC plants over the past couple of years. Historically, wild spawning rainbows were collected in that reach of river and spawn was taken in order to provide rainbows for other waters around the state. Right now we're using a captive broodstock at the Glenwood Springs hatchery to provide our HXC eggs, but a wild broodstock operation has more advantages if it's possible. For one, wild fish are all subjected to the natural selection pressures that are present in a wild environment, and so you should end up with a fish that is better adapted to that environment, in comparison to fish derived from a captive broodstock. It's also far cheaper to obtain eggs from a wild brood - all the hatchery costs associated with maintaining that captive broodstock go away. So I wanted to see if we're anywhere near even being able to consider the idea of collecting eggs at this location, or how many years out we might be.
     Anyway, on Monday, the 6th, we handled about 700 fish from the Byers Canyon bridge down to the downstream end of the public water at Lone Buck. About 100 of those were rainbows. That may not sound like much, but it's the largest proportion of rainbows I've ever picked up in any survey on the Colorado River  in my time. I don't have the population estimates calculated yet (won't for a long time) but it looks very encouraging. Only about two of the rainbows we collected appeared to be pellet pigs. Everything else had strong wild characteristics. Timing-wise, the biggest females (the ones around the 16" mark - these are apparently the 2010 year class that I stocked) were mostly spent. The year class younger than them, though, were still pretty green. This is the 2011 year class that I stocked, and they're up to about 12" now. They were by far the strongest year class present. I think a lot of those smaller females will go ahead and spawn this year - they're just running later since it's their first year.
     Take a look at this gorgeous 2010 male, ready to party:

     And here's an obligatory stomach-content series, a particularly awesome one at that:

     That guy had eaten his lunch in the more-traditional head-first manner, as opposed to those weirdos we ran a cross down at State Bridge the week before that were eating fish tail-first.

     All right, one other topic for today. A comment from Brian Young:

I was curious whether there had been any discussion about reintroducing stoneflies to the Upper Colorado. Sounds like they had good success down on the Arkansas with reintroduction, and they used Colorado River stoneflies. I know the water regs may still not allow for survival, but even that would be an important finding at some level. 

I could arrange for some private landowners (downstream from Lake Granby) to have the reintroduction done on their property if that is easier to control and evaluate than doing it initially on public water.

Brian Young

     Thanks Brian, that's a great question. It's an idea that we have been kicking around and it's definitely on the table. However, here's the short answer for the moment. The species we're talking about - Pteronarcys californica - is present in that area, just in such low numbers that they are not really noticeable, and they do not constitute a major food source for the trout at this time. But you can find them in low numbers if you look in the right spots. We know that was not the case historically. They used to be very dense and were the most important food source, all the way to the town of Granby and above. So something has changed drastically in the past 30 years. Each female produces around 1,000 - 1,400 eggs, according to the literature. So - knowing that we have a kind of sparse, "baseline" or "latent" population, if you will, that tells us that if the conditions were favorable, they would easily return to their historic densities on their own. The bottom line is that we've got a habitat problem in the river that far upstream. The cobble riffles where these guys live are heavily embedded. Until that changes, there is no reason to believe that they will be successful if we just dump a bunch more in that part of the river. That's a very different situation than down on the Arkansas. There, we know that metals wiped them out, and we know that the metals have since been cleaned up. Nothing has changed on the upper Colorado to improve the conditions for this species. However, the bright point on the horizon is that the mitigation agreements that are being hammered out with the water providers right now call for quite a bit of in-channel habitat work to address this exact issue. If and when that finally happens, we will absolutely be moving nymphs into the improved river channel reaches after the work is done. There is no reason to do so prior to that. Hopefully that makes sense.

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 . . . 

BOO-YAH!!! 

     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.