'Tis the season of preparing my stocking requests for 2014. I try to invest as much time as I can into finely tuning my stocking schedule, and I learn more every year. It takes a few years to really start to understand what to tweak and what to leave alone.
The way our stocking schedule works is like this: We have a centralized database (called "Trans 6") in which all the biologists submit their stocking requests. Around December 1, the database is opened to all the hatchery managers across the state, and they go through all the requests and select the ones that they can fill. Every hatchery is different in what it can produce and when. Each hatchery has a kind of "niche" that it tries to fill that it is best at. If the biologist who is making the stocking requests puts stuff in that no hatchery produces in that size, at that time, or both, then you end up with requests that don't get filled. So it's important to have a good understanding of what our hatcheries can and can't do.
In 2013, I stocked a grand total of 3,617,620 fish into waters in my area. 2,089,096 of those fish were kokanee from Glenwood. Aside from those 2 million kokanee, 70% of the rest of my fish came from Rifle Falls hatchery. It is our biggest and most productive hatchery, and so I need to coordinate as closely as possible with them when making my stocking requests.
In even years, we make our high lake plants with an airplane. I know that folks can get a little touchy about naming specific high lakes, so I won't do too much of that here. But I've made some changes, hopefully for the better. As I've said before on this blog, I really appreciate and want to encourage input from folks regarding alpine lakes. I have added lakes to the stocking schedule based on suggestions from anglers. I'm always looking for places we should be stocking to create a good alpine cutthroat fishery.
One lake that I'll name is Pacific Lake. I put in a request to stock grayling there this year. Pacific hasn't been stocked for a number of years and doesn't appear to support natural reproduction. I've had several people ask me about it though, and it seems like a good place to try some grayling.
I'd really like to track someone down who has been to Island Lake, in Grand County. I attempted to get there on a pack trip this year but didn't get past Gourd because of the weather. Island really takes some commitment to get to, as far as I can tell. We stocked it up through 1993, and haven't stocked it since. I can put it back on the schedule, but before I do that I want to know if there is a fishery there that is self-sustaining. We may not need to put it back on the schedule.
Another thing I'm going to try is some tiger trout in Meadow Creek reservoir. I've netted that lake twice since 2007, and both times it's been loaded with stunted brookies. They top out at 10" at most, and they are in poor body condition. Tigers have been used in these types of situations to control stunted brookies. So we'll see if that works out.
If you have any questions or input about high lake stocking and you don't want it to be seen by the general public, you can shoot me a private email at jon.ewert@state.co.us . As I was saying above, our high lake stocking program has benefitted from input I've received from high-lake enthusiasts. I can only make it to a few of them every year, and I've got a lot in my area.
Friday, November 15, 2013
Friday, November 8, 2013
Kokanee update
Just a quick update on kokanee egg collection. Up here in my neck of the woods, things are getting off to a very slow start. At Granby, we haven't seen fish arrive in any numbers at all yet. They're still running 300 or so CFS out of Shadow dam which makes things really difficult down there. I really have no idea what to expect up there this year.
We took spawn yesterday - Thurday, the 7th - at Wolford for the fifth time. We had 173 ripe females in the trap, which yielded 146,000 eggs. We're now up to about 350K for the year there. Wolford has had an excruciatingly slow start. However, Thursday was our biggest day yet and felt like the run has finally started to pick up. On Monday the 4th, we took 105 spawns. Each time we spawn we clear the trap out. So from Thursday the 31st (or previous spawn day) to Monday the 4th, we had an average of 26.25 ripe females per day swim into the trap. From Monday the 4th to yesterday (the 7th), we had an average of 57.7 females per day. So the rate of activity essentially doubled this week.
I'm very optimistic that this coming Monday will be our biggest day at Wolford yet this year. We've got Wolford covered for next year, but we would really like to see Wolford cover Williams Fork (need 360K eggs) and Granby (need 1.2 million). Last year Wolford did that. I don't know about this year, but I remain optimistic.
We've seen nothing encouraging yet at Granby, but we're going to try to take spawn there next Thursday and see what happens. At this point there is pretty much no possibility that Granby will cover itself.
From Vanish, regarding the last post about the whitefish in Parshall:
Neat! I bet they used to be in the upper colorado. Many anglers find them to be trash fish but I really enjoy taking a trip to NW CO once a year to fish for them. They can give a pretty good tussle.
Vanish, I agree with you that the whities get the short end of the stick from anglers sometimes. It hasn't always been that way.
But I want to address your first statement about whitefish occurring in the upper Colorado at some point. I want to make it absolutely clear that there is NO historical account - not from John Wesley Powell, any of the original settlers, any old-time surveyor - of whitefish ever occurring in the upper Colorado. We are certain that they are not native to the Colorado River. They are native to the White and Yampa rivers. They were first introduced into the Colorado and Roaring Fork rivers in Glenwood by Colorado Fish & Game in the 1910's. Prior to that introduction, they had not lived anywhere in the Colorado.
It may seem like a minor point, but I want to make sure that the biological significance of this is clear. Whitefish re-invading a place where they had previously lived would be a very different thing than whitefish pioneering a place they have never been. The latter scenario is the case here.
We seem to have two distinct whitefish populations on the Colorado: one upstream of Glenwood Canyon and one downstream. I honestly can't say if the whitefish up in the Pumphouse neighboorhood really originated from the historic stocking downstream from Glenwood Canyon. Another theory that I have has to do with a trans-basin diversion that takes water from Yamcolo Reservoir, which is loaded with a native whitefish population (being a tributary to the Yampa River). When they're running water through that ditch, it dumps into Egeria Creek, entering the Colorado River at McCoy. So, this is a trans-basin diversion. I don't know all the details but I do know that the owners of the water in that ditch use it to pay back water owed to the Colorado. So there can be a significant volume of water making that trip. It's entirely possible that larval or young whitefish from Yamcolo Reservoir have been entrained into that ditch, made their way down Egeria Creek and into the Colorado. It makes sense to me because that population of whitefish seems to have its "nucleus" in the vicinity of McCoy.
The original stocked whitefish around Glenwood came from the White River. If the above theory is true, we have White River whitefish downstream, and Yampa River whitefish upstream. We are not able to distinguish between the two genetically at this point, but it would be an interesting question to answer in the future. It would be a great subject for someone to do a masters' thesis on.
I can't figure out how to post PDF's on this blog. But here is a link to the Wild Trout Symposium that has an interesting article about whitefish. It's a huge document. But check out the article that starts on page 106, entitled "Becoming Trash Fish", about how people's perceptions of whitefish have changed over the past century. It's interesting stuff.
http://www.wildtroutsymposium.com/proceedings-10.pdf
We took spawn yesterday - Thurday, the 7th - at Wolford for the fifth time. We had 173 ripe females in the trap, which yielded 146,000 eggs. We're now up to about 350K for the year there. Wolford has had an excruciatingly slow start. However, Thursday was our biggest day yet and felt like the run has finally started to pick up. On Monday the 4th, we took 105 spawns. Each time we spawn we clear the trap out. So from Thursday the 31st (or previous spawn day) to Monday the 4th, we had an average of 26.25 ripe females per day swim into the trap. From Monday the 4th to yesterday (the 7th), we had an average of 57.7 females per day. So the rate of activity essentially doubled this week.
I'm very optimistic that this coming Monday will be our biggest day at Wolford yet this year. We've got Wolford covered for next year, but we would really like to see Wolford cover Williams Fork (need 360K eggs) and Granby (need 1.2 million). Last year Wolford did that. I don't know about this year, but I remain optimistic.
We've seen nothing encouraging yet at Granby, but we're going to try to take spawn there next Thursday and see what happens. At this point there is pretty much no possibility that Granby will cover itself.
From Vanish, regarding the last post about the whitefish in Parshall:
Neat! I bet they used to be in the upper colorado. Many anglers find them to be trash fish but I really enjoy taking a trip to NW CO once a year to fish for them. They can give a pretty good tussle.
Vanish, I agree with you that the whities get the short end of the stick from anglers sometimes. It hasn't always been that way.
But I want to address your first statement about whitefish occurring in the upper Colorado at some point. I want to make it absolutely clear that there is NO historical account - not from John Wesley Powell, any of the original settlers, any old-time surveyor - of whitefish ever occurring in the upper Colorado. We are certain that they are not native to the Colorado River. They are native to the White and Yampa rivers. They were first introduced into the Colorado and Roaring Fork rivers in Glenwood by Colorado Fish & Game in the 1910's. Prior to that introduction, they had not lived anywhere in the Colorado.
It may seem like a minor point, but I want to make sure that the biological significance of this is clear. Whitefish re-invading a place where they had previously lived would be a very different thing than whitefish pioneering a place they have never been. The latter scenario is the case here.
We seem to have two distinct whitefish populations on the Colorado: one upstream of Glenwood Canyon and one downstream. I honestly can't say if the whitefish up in the Pumphouse neighboorhood really originated from the historic stocking downstream from Glenwood Canyon. Another theory that I have has to do with a trans-basin diversion that takes water from Yamcolo Reservoir, which is loaded with a native whitefish population (being a tributary to the Yampa River). When they're running water through that ditch, it dumps into Egeria Creek, entering the Colorado River at McCoy. So, this is a trans-basin diversion. I don't know all the details but I do know that the owners of the water in that ditch use it to pay back water owed to the Colorado. So there can be a significant volume of water making that trip. It's entirely possible that larval or young whitefish from Yamcolo Reservoir have been entrained into that ditch, made their way down Egeria Creek and into the Colorado. It makes sense to me because that population of whitefish seems to have its "nucleus" in the vicinity of McCoy.
The original stocked whitefish around Glenwood came from the White River. If the above theory is true, we have White River whitefish downstream, and Yampa River whitefish upstream. We are not able to distinguish between the two genetically at this point, but it would be an interesting question to answer in the future. It would be a great subject for someone to do a masters' thesis on.
I can't figure out how to post PDF's on this blog. But here is a link to the Wild Trout Symposium that has an interesting article about whitefish. It's a huge document. But check out the article that starts on page 106, entitled "Becoming Trash Fish", about how people's perceptions of whitefish have changed over the past century. It's interesting stuff.
http://www.wildtroutsymposium.com/proceedings-10.pdf
Thursday, October 24, 2013
A new species in Parshall
On September 24 & 27, we ran our annual raft electrofishing survey of the Parshall-Sunset reach, AKA the Kemp-Breeze State Wildlife Area. I always consider this to be probably the single most important data set that I collect every year, for the simple reason that it is one of the longest-running big river trout population data sets that exists in the state. Our researcher Barry Nehring was the first biologist in Colorado to start running raft electrofishing surveys, in the late '70's. He had gone up to Montana, where they had figured out how to do it. 1981 was the first year that he surveyed the Parshall-Sunset reach, so as of this year that data set is 32 years old. It's been done the same way, at the same time of year all those years.
Speaking of Barry Nehring, I often like to say that I owe my career to a series of phenomenal mentors. I did not arrive in this job by the traditional route of attending graduate school in fisheries. Instead, three years out of college when I was trying to figure out my next move, I stumbled into my first permanent job as a wildlife officer for our agency. After five years I transferred into the biologist job. My goal was always to work as a fisheries biologist; I just arrived here via a slightly different route than most. It's not unprecedented - I've got coworkers who took the same route. But what I was getting at, is that I am constantly thankful for the series of spectacular mentors that I have worked with in the fisheries field. These are guys that I feel so lucky for every day that I have worked side-by-side with. It's the knowledge that I was able to glean off of them that got me where I am today. Barry is one of those guys. It seems that quality mentorship may be slowly fading away in the professional world, and if that's truly the case it's a sad, sad thing.
Anyway, I digress. I haven't worked up the data yet from the Parshall reach, but thought I would share a couple of things. First of all, it looks like the density for large fish (>14") is as low as it has ever been, and at this point may be flirting with dropping below the gold medal standard of at least 12 fish per surface acre greater than 14 inches. That is really bad news, for a reach of river that not very long ago supported densities in the neighborhood of 100 or more per acre. Numbers of rainbows in that size category are up, which is good news, but browns are way down. I don't have a precise explanation for it at the moment, but we can get into that over the winter.
But here is the really sensational tidbit that I wanted to share for now. On our first day, the mark run on the 24th, I was working fish out of the tank and picked up this little 3-inch silvery thing. I immediately said "kokanee" because every once in a while we pick up the occasional small kokanee that got flushed out of one of the reservoirs. However, as soon as I said it, I realized that was not what I was looking at. I said, "Wait--" and the other guys on the boat looked, and three of us said in unison, "MOUNTAIN WHITEFISH !?!?"
We have NEVER captured a mountain whitefish anywhere upstream of Gore Canyon. Thirty years of one of the most intensively studied trout rivers in this state, and not a SINGLE record of a mountain whitefish. Not just in the Colorado, but not in any tributary, any lake or reservoir, nowhere in the Blue River watershed. In the entire time I've been here, I've taken it for granted that Gore Canyon is the natural upstream barrier of whitefish on the Colorado. There are a lot of them below, and there are none above. That is simply the way that it is and what we have observed in the entire historical record. But here was this little three-inch fish in my hand that was very definitely a mountain whitefish, no question about it.
The weird thing about it is, this is not a species that people move around. When a new species pops up in an unexpected place, it is almost always the result of either deliberate or accidental introduction by people. But I just can't see someone willfully moving mountain whitefish from a lower section of the Colorado to the upper section, and I have a hard time picturing how it would happen on accident. I didn't know what to make of it, and chalked it up to just one of those crazy anomalies that keeps us humble. A one-time occurrence that I probably would never run across again.
Three days later, on the 27th, we ran our recap run on the same reach. You'll never guess what we picked up right in the Parshall Hole. Not one - not two - but THREE young-of-the-year mountain whitefish. Three of them. I was just flabbergasted, and remain so today.
So here is my theory for the moment. We just came through two extremely unusual years flow-wise. 2011 was an insanely high-water year, and 2012 was an insanely low-water year. I think that if whitefish were to make it through Gore Canyon, it would be more likely to happen during high water than low water. I'm thinking that maybe a few adults managed to find their way through in 2011. We have never run across the adults, but now we have found their offspring.
There is a good lesson in humility for me in this. At some point over the past year, I was talking with someone who told me that their friend caught what he was sure was a mountain whitefish somewhere above Gore Canyon. I don't remember who it was or exactly where the person was fishing. But it was a secondhand report that came to me. Secondhand reports are never very reliable, and I basically brushed it off because there are many examples of incorrect species identification by anglers. I can't tell you how many times I've talked to people who don't know the difference between a whitefish and a white sucker. So, whoever it was that told me that, if you're reading this please drop me a line so I can get those details again, and you can watch me eat a little crow.
If whitefish proliferate in the upper Colorado, it could change the ecology of the river significantly. There would be some benefits to the sport fishery and some potential drawbacks. It will be fascinating to see if they manage to get a foothold here. If they do, 2013 will be a milestone marking the end of the "pre-whitefish" era and the beginning of the "post-whitefish" era.
Speaking of Barry Nehring, I often like to say that I owe my career to a series of phenomenal mentors. I did not arrive in this job by the traditional route of attending graduate school in fisheries. Instead, three years out of college when I was trying to figure out my next move, I stumbled into my first permanent job as a wildlife officer for our agency. After five years I transferred into the biologist job. My goal was always to work as a fisheries biologist; I just arrived here via a slightly different route than most. It's not unprecedented - I've got coworkers who took the same route. But what I was getting at, is that I am constantly thankful for the series of spectacular mentors that I have worked with in the fisheries field. These are guys that I feel so lucky for every day that I have worked side-by-side with. It's the knowledge that I was able to glean off of them that got me where I am today. Barry is one of those guys. It seems that quality mentorship may be slowly fading away in the professional world, and if that's truly the case it's a sad, sad thing.
Anyway, I digress. I haven't worked up the data yet from the Parshall reach, but thought I would share a couple of things. First of all, it looks like the density for large fish (>14") is as low as it has ever been, and at this point may be flirting with dropping below the gold medal standard of at least 12 fish per surface acre greater than 14 inches. That is really bad news, for a reach of river that not very long ago supported densities in the neighborhood of 100 or more per acre. Numbers of rainbows in that size category are up, which is good news, but browns are way down. I don't have a precise explanation for it at the moment, but we can get into that over the winter.
But here is the really sensational tidbit that I wanted to share for now. On our first day, the mark run on the 24th, I was working fish out of the tank and picked up this little 3-inch silvery thing. I immediately said "kokanee" because every once in a while we pick up the occasional small kokanee that got flushed out of one of the reservoirs. However, as soon as I said it, I realized that was not what I was looking at. I said, "Wait--" and the other guys on the boat looked, and three of us said in unison, "MOUNTAIN WHITEFISH !?!?"
We have NEVER captured a mountain whitefish anywhere upstream of Gore Canyon. Thirty years of one of the most intensively studied trout rivers in this state, and not a SINGLE record of a mountain whitefish. Not just in the Colorado, but not in any tributary, any lake or reservoir, nowhere in the Blue River watershed. In the entire time I've been here, I've taken it for granted that Gore Canyon is the natural upstream barrier of whitefish on the Colorado. There are a lot of them below, and there are none above. That is simply the way that it is and what we have observed in the entire historical record. But here was this little three-inch fish in my hand that was very definitely a mountain whitefish, no question about it.
The weird thing about it is, this is not a species that people move around. When a new species pops up in an unexpected place, it is almost always the result of either deliberate or accidental introduction by people. But I just can't see someone willfully moving mountain whitefish from a lower section of the Colorado to the upper section, and I have a hard time picturing how it would happen on accident. I didn't know what to make of it, and chalked it up to just one of those crazy anomalies that keeps us humble. A one-time occurrence that I probably would never run across again.
Three days later, on the 27th, we ran our recap run on the same reach. You'll never guess what we picked up right in the Parshall Hole. Not one - not two - but THREE young-of-the-year mountain whitefish. Three of them. I was just flabbergasted, and remain so today.
So here is my theory for the moment. We just came through two extremely unusual years flow-wise. 2011 was an insanely high-water year, and 2012 was an insanely low-water year. I think that if whitefish were to make it through Gore Canyon, it would be more likely to happen during high water than low water. I'm thinking that maybe a few adults managed to find their way through in 2011. We have never run across the adults, but now we have found their offspring.
There is a good lesson in humility for me in this. At some point over the past year, I was talking with someone who told me that their friend caught what he was sure was a mountain whitefish somewhere above Gore Canyon. I don't remember who it was or exactly where the person was fishing. But it was a secondhand report that came to me. Secondhand reports are never very reliable, and I basically brushed it off because there are many examples of incorrect species identification by anglers. I can't tell you how many times I've talked to people who don't know the difference between a whitefish and a white sucker. So, whoever it was that told me that, if you're reading this please drop me a line so I can get those details again, and you can watch me eat a little crow.
If whitefish proliferate in the upper Colorado, it could change the ecology of the river significantly. There would be some benefits to the sport fishery and some potential drawbacks. It will be fascinating to see if they manage to get a foothold here. If they do, 2013 will be a milestone marking the end of the "pre-whitefish" era and the beginning of the "post-whitefish" era.
Tuesday, October 15, 2013
Kokanee season
I'm fully immersed in chasing kokanee eggs at the moment. Things are not looking quite as rosy this year statewide, and we have a good chance of coming up a bit short. By this date last year, Blue Mesa had produced 2.5 million already; prior to today, they were sitting at right about half of that, at 1.2 million. I think it's safe to say that they're not going to have another record-breaking year. Hopefully I'm wrong about that.
Up here, things are looking decidedly worse. As for Williams Fork, all our indicators tell us that whatever run takes place will be very weak. My best estimation is that we would get about half the eggs we got in 2011 - which would be approximately 300K. That's the best-case scenario. That operation is extremely labor-intensive. If you've never seen it, I have to build an electric barrier in the river to stop upstream migration, which means that I have to hire a dedicated person to live in a camper there and monitor the thing around the clock. 300,000 eggs is not worth that much expense and manpower. So, we're not putting the trap in at WF this year. The buoy line is in and the fishing closure is in effect, but the purpose of that is to allow us to get our disease sample. We have to keep a disease history current to continue to use it as an egg source in the future. That involves getting ovarian fluids and a couple other biopsies from 60 females. Once we have that, we'll pull the buoy line. Hopefully that will happen by the 25th. We haven't seen a fish running there yet. My first year here, 2007, we took 4.5 million eggs from Williams Fork. Crazy how times change.
Granby is not looking much better. Last year, we scraped and scraped for 800,000 eggs. That was the first time in over a decade that Granby did not provide enough eggs for itself - we need 1.2 million there to break even. Our projections for this year suggest a continued decline, and I will feel lucky if we get half a million there.
It's also a weird year for Granby with the water regime. When the floods started happening around September 11, the water entities immediately stopped taking water through the tunnels to the east slope. There hasn't been any water going through the Adams, Moffat, or Roberts tunnels since the floods. Because of that, all of a sudden we've got a lot more water in certain places where there is never water this time of year. One of those places is below Shadow Mountain dam. It's sitting at 200 CFS right now, when normally at this time of year they're releasing 40. The only control they have on the elevations of Grand and Shadow right now is releases out of Shadow Mountain dam. Normally there is a lot of water going through the Adams Tunnel this time of year. At one brief point in September, Shadow dam was spilling 1600 CFS. Our whole kokanee trap system there is designed to handle 40 CFS, and it's always a very controlled, steady situation, except for this year. We're way late on getting a trap in the river there. So, tomorrow they're going to cut releases for us for a few hours while we jump in the river and get a trap built that can handle 200-300 CFS. When we're done they'll crank it back up and we'll stand there with our fingers crossed hoping that it holds. It's a good problem to have; I shouldn't complain.
The one bright spot in this neighborhood is Wolford. We have every reason to believe that I'll take just as many eggs there this year as I did last year - 1.9 million. Over the past year we built a new and improved Merwin trap which corrected some of the design flaws of the original one that we used. We set it yesterday, and this morning there were 100 or so kokes in it. That's a good sign. We'll start taking eggs there on Monday, and we'll be taking every egg we can get out of Wolford. Our biggest day there last year was November 20, so we'll be sticking with it for a while, and in fact Wolford will probably be the lake that saves our bacon for kokanee up here.
Here is the disturbing trend for kokanee in Colorado: fewer and fewer lakes are able to support them. My mantra for kokanee the past few years has been "Competitors, Predators, and Parasites." That is, I'm not aware of a single lake in the state with a viable kokanee population that has all three of those things. In my time here, I've seen both Williams Fork and Green Mountain go from one to two, and the kokanee populations at both those lakes have taken a major hit. The only lake I've got left with none of those three things is Wolford - assuming we can stay on top of the pike population there. If the pike take off, or gill lice were to get into Wolford, I'm afraid we'd be done with kokanee in this area. We keep turning away from problem reservoirs as egg sources, and it feels an awful lot like we're backed into a corner now.
Up here, things are looking decidedly worse. As for Williams Fork, all our indicators tell us that whatever run takes place will be very weak. My best estimation is that we would get about half the eggs we got in 2011 - which would be approximately 300K. That's the best-case scenario. That operation is extremely labor-intensive. If you've never seen it, I have to build an electric barrier in the river to stop upstream migration, which means that I have to hire a dedicated person to live in a camper there and monitor the thing around the clock. 300,000 eggs is not worth that much expense and manpower. So, we're not putting the trap in at WF this year. The buoy line is in and the fishing closure is in effect, but the purpose of that is to allow us to get our disease sample. We have to keep a disease history current to continue to use it as an egg source in the future. That involves getting ovarian fluids and a couple other biopsies from 60 females. Once we have that, we'll pull the buoy line. Hopefully that will happen by the 25th. We haven't seen a fish running there yet. My first year here, 2007, we took 4.5 million eggs from Williams Fork. Crazy how times change.
Granby is not looking much better. Last year, we scraped and scraped for 800,000 eggs. That was the first time in over a decade that Granby did not provide enough eggs for itself - we need 1.2 million there to break even. Our projections for this year suggest a continued decline, and I will feel lucky if we get half a million there.
It's also a weird year for Granby with the water regime. When the floods started happening around September 11, the water entities immediately stopped taking water through the tunnels to the east slope. There hasn't been any water going through the Adams, Moffat, or Roberts tunnels since the floods. Because of that, all of a sudden we've got a lot more water in certain places where there is never water this time of year. One of those places is below Shadow Mountain dam. It's sitting at 200 CFS right now, when normally at this time of year they're releasing 40. The only control they have on the elevations of Grand and Shadow right now is releases out of Shadow Mountain dam. Normally there is a lot of water going through the Adams Tunnel this time of year. At one brief point in September, Shadow dam was spilling 1600 CFS. Our whole kokanee trap system there is designed to handle 40 CFS, and it's always a very controlled, steady situation, except for this year. We're way late on getting a trap in the river there. So, tomorrow they're going to cut releases for us for a few hours while we jump in the river and get a trap built that can handle 200-300 CFS. When we're done they'll crank it back up and we'll stand there with our fingers crossed hoping that it holds. It's a good problem to have; I shouldn't complain.
The one bright spot in this neighborhood is Wolford. We have every reason to believe that I'll take just as many eggs there this year as I did last year - 1.9 million. Over the past year we built a new and improved Merwin trap which corrected some of the design flaws of the original one that we used. We set it yesterday, and this morning there were 100 or so kokes in it. That's a good sign. We'll start taking eggs there on Monday, and we'll be taking every egg we can get out of Wolford. Our biggest day there last year was November 20, so we'll be sticking with it for a while, and in fact Wolford will probably be the lake that saves our bacon for kokanee up here.
Here is the disturbing trend for kokanee in Colorado: fewer and fewer lakes are able to support them. My mantra for kokanee the past few years has been "Competitors, Predators, and Parasites." That is, I'm not aware of a single lake in the state with a viable kokanee population that has all three of those things. In my time here, I've seen both Williams Fork and Green Mountain go from one to two, and the kokanee populations at both those lakes have taken a major hit. The only lake I've got left with none of those three things is Wolford - assuming we can stay on top of the pike population there. If the pike take off, or gill lice were to get into Wolford, I'm afraid we'd be done with kokanee in this area. We keep turning away from problem reservoirs as egg sources, and it feels an awful lot like we're backed into a corner now.
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.
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.
Sunday, June 9, 2013
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.
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.
Sunday, June 2, 2013
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:
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.
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