Sunday, April 28, 2013

Colorado River: Lyons Gulch and Catamount

     Last week we spent our first four-day stint of the year running electrofishing surveys on the Colorado. We use two rafts with electrofishing gear, working in tandem because of the size of the river. There are three people on each raft, so it takes a crew of six. This is an annual team effort with my downstream counterpart out of Glenwood, Kendall Bakich. We have set up four, two-mile reaches on the river that are roughly equally spaced, between Pumphouse and Dotsero. We're surveying all four of them this year. We use a mark-recapture method of population estimation, which means that each reach takes two days to complete - a mark day and a recapture day. 
     We're working downstream to upstream, so first on tap was the Lyons Gulch station. This is about six miles upriver from Dotsero. We've been surveying this reach only every other year. We surveyed it last year, but did it again this year because there was a horrendous, catastrophic flash flood event in the area last year, in early July. So, it just so happened that we had good data showing what was present prior to the flood event (in April 2012), and now we have good data from April 2013, after the event.
     By pure coincidence, I happened to be in Glenwood Springs on a family trip the weekend that flash flood occurred last summer. I've never seen a debris flow like that. It looked like a volcano had erupted somewhere upstream. After about 24 hours of solid debris flow the fish carcasses started coming down. There were tens of thousands of fish carcasses on the surface of the water, flowing through Glenwood Canyon. I've never seen anything like it. It was astounding. 
     You can see the remnants of that flood event if you drive the river road up from Dotsero. From approximately Deep Creek to Red Dirt Creek, every nameless gully coming in from the north dumped massive amounts of material. The size of some of the boulders that moved is impressive.
     Anyway, in kind of an ironic way we felt lucky because this is a rare opportunity to observe firsthand what changes have taken place in the fish populations as a result of such a huge disturbance. Needless to say, the fish population is way down. On our mark run on Monday, in our boat we only handled about 130 fish. That is an extremely low number to get from two miles of river on this type of a survey. We don't have any of the data worked up yet, but when we do it will show big reductions of all species. (Except for rainbows - Kendall stocked a bunch of catchables after the flood to provide some kind of fishery. They're still around.) The thing that was the most interesting to me, though, is that the species composition seems to be approximately the same - all the fish that have been present in that section are still there: whitefish, browns, flannelmouth suckers, white suckers, and hybrid suckers. It's just that all their numbers are down drastically, across the board. I had some expectation that the flood would have affected different species differently and that we would see an altered species composition as a result. But that doesn't appear to be the case. So the good news there is that everything is going to come back; it will just take a few years.
     Catamount was beautiful as always. I really enjoy that section of river. Numbers of fish were impressive and we finally enjoyed some decent weather. Below are some pictures, courtesy of Mike Kline, of the Catamount run.

We did find a few wild rainbows like the one above. Look at that nice white tip on the anal fin. We don't stock fish anywhere near this stretch.

Ahhh, springtime on the river.

     This week we'll continue upriver to our two upper stations: State Bridge and Radium. The State Bridge station is brand new- it's never been surveyed so we have no data at all on what the fish populations are in that section. We decided to add this one because it splits the difference geographically between the already-established Radium and Catamount stations, and because the new ramp at Two Bridges north of Bond is changing traffic patterns on the river. The section from State Bridge through Bond is suddenly far more accessible because of the new ramp. This will only increase as float fisherman continue to realize that they can separate themselves from the whitewater crowd on this reach. So, we want to get a handle on what the fish populations look like there, and if they undergo any changes over the next several years.
     I've had some good comments and questions lately. Keep them coming. I'm saving them up for a slower week when I'll do another "grab bag" and address a few different topics that you have brought up in the comments. As I've always said, this thing will be much better if there is two-way communication going on.

Sunday, April 21, 2013

More stoneflies for the Arkansas.

    Whether or not the weather cooperates, field season is upon us. We've already completed our first little project of the year, which was to get another batch of Pteronarcys stoneflies from the Colorado River to transplant over to the Arkansas. These bugs were native to the Arkansas before acid mine drainage wiped them out. The Arkansas has been cleaned up enough in modern times that it looks like they could survive there again. So last year my friend and counterpart in Salida, Greg Policky, came up with the idea of making these transplants.
     In 2012 we collected about 37,000 nymphs from the Colorado to transport to the Arkansas. This year, over two days of collection we managed to gather about 50,000 nymphs. Greg transplanted all these nymphs to four specific riffles with good habitat on the Arkansas. He did observe adults hatching last year. So now it's just a question of whether or not there are enough adults to find each other once they do hatch and look for mates. 
     Here are some photos of this year's collection efforts. They were taken by Mike Kline, who is working with me as a field technician this spring.

     Here we are trying to become enthusiastic about getting in the river on a less-than-pleasant day.

     Any day in the field is better than any day in the office, though, right? Sometimes we have to remind ourselves of that repeatedly.
     Here's the collection process. It's just a matter of rolling rocks in the places with just the right depth and velocity. You quickly get a feel for finding the "sweet spots" that hold a lot of nymphs.

     When you roll a good rock, your net looks like this.

     High-quality trout food.

     As field season progresses, my approach to these posts is going to change a bit. My year basically runs in two modes: data collection mode and data analysis mode. What you've been seeing up to this point is the result of the data analysis part of my year. Now that field season is here, I don't do a lot of data analysis. So these posts are going to become more of a journal of what my weeks entail, and what interesting things we ran across. Keep posting questions - this is going to be a much better resource for everyone if there is two-way communication here. So I appreciate that and it helps guide me as far as what topics are of interest to people.
    On tap for the next two weeks is eight days of spring raft electrofishing surveys on the Colorado. We're surveying four, two-mile reaches that are roughly evenly spaced between Pumphouse and Dotsero. Here's hoping that the weather doesn't treat us too miserably.


Sunday, April 14, 2013

Dillon, part 2: the char experiment

     On to the subject of arctic char in Dillon Reservoir. The idea of stocking char in Dillon originated well before my time. As the '80's wore on into the '90's, it was obvious that Dillon was entering into an "aging reservoir" period, where the fishery was becoming less and less productive. This is not unusual in artificial impoundments, but it did seem to be more pronounced in Dillon than many other places. One thing that Dillon did have was mysis. Densities of mysis seemed to be relatively consistent - more so than Granby. There are a lot of reservoirs in Scandanavia where the fishery consists of arctic char which prey on mysis. Dillon resembles these lakes as much as anything, and this is where the idea of trying arctic char in Dillon was born. 
     The first char stocked in Dillon were in 1990. Here is the stocking history of char in the lake from 1990-1998: 

11/14/1990     12,751 fish     4.3" avg. length
7/15/1992       125 fish          19" (must have been brood fish)
7/15/1996       56,501            2.0"
11/20/1998     6,754             3.9"

     As you can see, this is an extremely inconsistent stocking history. I have no idea what the story was on the 125 big fish stocked in 1992, because I am not aware that we ever had a brood stock in captivity.  The 1990 and 1998 fish were stocked at a strange time of year, when you wouldn't necessarily expect to get a lot of survival out of a fingerling plant. I'm sure this was a result of the timing of egg availability. It seems that the only plant that really hit the mark was the 1996 one, going into the lake in July with a good number of fish. 
     So, when I got here there was already a discussion going regarding making a second try with char at Dillon. One question that has been asked of me is, "If they didn't work out the first time, why should they work if we try them again?" The answer to that question is obvious if you look at the stocking history. They were never given what I would consider a full chance. 
     In 2007, we found what looked like a good egg source in Canada. We have to buy the eggs outright, so there is a limit to how many eggs we can get. We've been buying 50K eggs every year since then. There is a pretty high mortality rate - 50K eggs do not result in 50K fish. Here is the stocking history since 2008:

     This is a much more consistent stocking history than what was tried before. We've (in particular the crew at the Shavano hatchery in Salida) gone to a lot of effort to make this happen annually. These are not large numbers for a reservoir the size of Dillon. My primary goal in stocking these fish is not to directly produce a sport fishery with them - it's to get enough char into the lake that they hopefully can find each other when the romantic time of year rolls around, get some successful reproduction going, and establish a self-sustaining fishery. 
     Enter Devin Olsen. Devin is a CSU student working on getting his Master's degree in fisheries. He is studying the success (or possibly the lack thereof) of char in Dillon Reservoir. Over the past couple of years he's figured out some important facts. The char are definitely feeding on mysis, which is good. But the real kicker is some data he's got that is hot off the presses: Out of approximately 60 char that he netted out of the reservoir in 2012, 45% of them were stocked, and 55% of them were born in the lake. This is the first time that natural reproduction has been proven beyond a shadow of a doubt. Devin also picked up two fish this past year that would have broken the old state record, but since he was collecting them for research purposes neither of them were entered as a new record. Below is a picture he took of a nice male.

     The char are still sparse in the lake, but we now know that they're reproducing. We might be approaching a period of time when the population growth becomes exponential and they start to turn up in a lot of new areas in the lake. So far it appears that they rarely venture into shallow areas, and seem to stick to deeper habitat year-round. 
     No one has figured out how to catch them during the summer yet. A handful of guys have got them dialed in through the ice during a narrow window of opportunity in the winter, but I'm not aware of a single char being caught out of the open water yet. That is the challenge for some enterprising reader out there - be the pioneer in figuring out how to catch these guys in the summer. 
     I have been asked multiple times why we won't stock lake trout in Dillon. There are many reasons, but the biggest one is that we need to see how this fishery is going to develop. There are many waters in every direction from Dillon to fish for lake trout. But Dillon Reservoir is the ONLY PLACE in the lower 48 states outside of MAINE that these fish can be caught. We are constantly criticized by certain sectors of the angling public for what is perceived as managing our fisheries with too narrow a focus and not providing enough diversity of opportunity in terms of species. Isn't this worth something? I think it's worth a lot.

Sunday, April 7, 2013

Dillon, part 1

     All right, I've been asked to get into Dillon Reservoir a number of times. I've been holding out because we had a meeting this past week regarding Dillon and I wanted to wait for new information. There's a lot to talk about with Dillon, so we'll take it one topic at a time.
     First of all, let's talk about the browns. Historically, Dillon enjoyed the status of having a trophy brown trout fishery. It was a destination, and people would travel to Dillon specifically to fish for the large (4-6 lbs or more or larger) browns. All reservoirs experience a reduction in productivity as they age, and Dillon is no different. It is definitely less productive now and the highly visible trophy brown trout fishery has declined over the past couple of decades. However, it is not gone entirely, and in fact has been showing some signs of resurgence lately. The brown trout population in Dillon is actually pretty dense - more dense than any of the other reservoirs in my area. We don't stock any at all; they're all the product of natural reproduction. the problem is, they just don't have anything to eat, and so they tend to be very skinny, and there has been somewhat of a "growth barrier" right around the 15-inch mark.

     The figure above shows the size distribution of brown trout in my 2008 gillnet survey. I'm using 2008 as an example because it's the most pronounced drop between 15-inch fish and 16-inch fish. But that drop exists in all the gillnet sampling I've done. I've only been netting Dillon every other year, with six overnight gillnets in established locations. Picking the suckers out of the nets is just too much of an ordeal to do it every year, and things don't change that much on an annual basis to necessitate netting it every year.
     Speaking of suckers, here's the species composition from 2012 in the gillnets, by percent:

     Every gillnet sample is very similar in this regard too. Here is a graph showing body condition by size in the brown trout population. There are multiple years' samples on this graph, pooled together.

     Because of that apparent growth barrier that I mentioned above, I ran trend lines for these fish as if they were two different populations. What we see at Dillon consistently over the years is that body condition in the brown trout declines as the fish approach 16 inches. Only a small percentage of the fish make it beyond the 16-inch mark, but the ones that do exhibit increasing body condition the larger they get. The reason for this is most likely that those few fish making it beyond 16" figure out how to prey on the 10" catchable rainbows that we stock annually. Brown trout will eat other fish half their length (or sometimes even larger), and there are some runts in those catchable batches that run as small as 8". 
     I'll talk about arctic char next week, but for now I'll finish off with a shot of the largest brown we picked up in the gillnet survey last summer. It went 24" and weighed a whopping 9.3 pounds, which calculates to a relative weight of 177. A very fat fish. So, rest assured that there are still fish like this out there.