Friday, February 5, 2016

Green Mountain timeout, part 1.

     I'll start with the good news about Green Mountain before getting into the bad news.  Last June, I spent four days out there running gillnet surveys.  We set 40 gillnets in random locations all over the lake, for six hours apiece. Over the course of that survey we handled 86 lake trout. These lakers looked the best that I have seen them at Green Mountain over the past decade. Below is the size distribution of the lake trout that we caught.
     Out of all the times I have run gillnet sampling on Green Mountain, 2015 gave us the highest catch rate of fish greater than 24", and the average size of all the lake trout caught was the largest. In the four years prior to 2015, when running these surveys, I caught an average of one lake trout over 24" for every 23 hours of gillnet soak time (we have 8 gillnets fishing simultaneously, so each day we're out there we get 48 hours of gillnet soak time). In 2015, I caught one for every 10 hours. 
     Also, when we look at relative weights of lake trout, fish over 24" at Green Mountain are in consistently better condition than fish under 24". Below is the relative weight plot from 2015 to illustrate that. Body condition for fish less than 24" averaged 72.1, while fish larger than 24" averaged 95.7. In fact, we have seen this relationship - increasing body condition as the fish get larger - for all of the past 5 years there. However, the difference between the two groups in 2015 - 23.6 points - is the largest gap that I have observed there. Another way to put it would be to say that the trend line on the graph below has the steepest slope out of any of the years that I have surveyed GM.
     All this information means a lot more when you compare it with other lakes. At Granby, fish over 24" have consistently POORER body condition than fish under 24". Below is the relative weight plot for all the Granby lake trout that I have weighed (899 fish) from 2011-2015. 
     Across all those years, relative weights for the Granby fish less than 24" was 82.7, and for fish larger than 24" was 77.1. I have searched our database and run this calculation for many of the lake trout waters across the state including Jefferson, Taylor, Ruedi, Twin, Turquoise, Blue Mesa, and Williams Fork (of course). The fact is, Granby is the ONLY lake trout fishery in the state that sees a consistently lower (and statistically significant if that matters to you) body condition in large fish than in small fish. 
       Here's how it works out in pounds of fish. Based on these length-weight relationships, the average 30" fish at Green Mountain weighs 10 lbs., while a Granby fish of the same size weighs 8.6 lbs. A 36" fish at Green Mountain averages 18.6 lbs., while a Granby fish of that size averages 15.1. And if you take it up to 40", a Green Mountain fish will average 26.7 lbs., while the Granby fish weighs in at 21. The result of poor body condition in these large fish is extremely slow-or zero- growth in length over time, and less egg production. The population seems to become "decadent" in a way, like an overgrown forest that has suffered from a lack of disturbance and renewal. We've all seen what that results in. 
     You may remember that we changed the harvest regulation at Green Mountain Reservoir beginning in January of 2011. We increased the bag limit of lake trout to 8 fish of any size, separate from the bag limit of other trout. There is no size restriction of any kind on the 8 fish bag.  In the years since that regulation change, I regularly ask the game wardens as well as other folks around Green Mountain if people are taking advantage of the 8-fish bag on lake trout and harvesting limits of them. The answer has always been that they absolutely are. As far as we can tell, anglers have been taking full advantage of the increased bag limit there since we enacted it.
     I'll take this opportunity to point out a statement that I wrote in the 2010 issue paper which proposed to increase the lake trout limit:

"This population should easily sustain increased harvest rates, and may exhibit increased quality as a result of the thinning effect that increased harvest may produce."


     I'm not making the claim that my recent data at Green Mountain is unequivocal proof of the above statement, and that my data isn't subject to any of the possible pitfalls of such a data set. However, I will say that this data gives me good confidence that the probability of the above statement being correct is far higher than the probability of it being incorrect.
     This is the stuff that a fisheries biologist bases his/her decisions on, in combination with other sources of information such as public input.  One of the main purposes of this blog is to try to fully expose the reasoning that goes into my - and any biologist's - fishery management decisions.  Even though it goes on in my head and across countless spreadsheets and databases, it's a public process. It's what you pay me to do when you buy a fishing license. And  for that, I have to say a heartfelt "thanks" because I love my job very, very much. Entering my tenth year here, I still have to pinch myself nearly on a daily basis and make sure I'm not dreaming. I consider myself to be extremely lucky to have this job.
     Anyway, I digress.  What I was getting at is that I think there is a little bit of an information gap in the world when it comes to making the details of this stuff accessible to the public. It mainly appears in the pages of specialized scientific fisheries journals that people typically don't have easy access to. I believe one reason that there's not that much of it out there is because as a group, we biologists tend to assume that there is not general interest among the public in this level of detail. But I think that there is a sector of the angling public that is interested in as much detail as we're willing to take the time to give. It may not be the majority of license buyers, but a decent slice of them, I think.  That's the group of anglers that this blog aims to serve. There will always be a majority of people who have no interest in the fact that there is a lot of effort, consideration, and decision-making behind each and every fish that they find on the end of their line.  I'm not going to reach those people no matter what, and that's fine.
     There's a selfish motivation to do this also - it makes me a better biologist to work this stuff out in written form. Makes me consider things more thoroughly and carefully.
     I'm going to hold off on the bad news about Green Mountain until my next post.

Sunday, January 24, 2016

2015 favorite fishing moments

     Greetings all, and welcome to 2016. One of my goals this year is to revive this blog. I'm committing to posting once a month. I started out with weekly posts, then slipped to every two weeks, and now I'm going to try monthly posts. I should be able to sustain that. 
      The main reason I lost motivation with the blog is that in 2014 I held a couple of public meetings in which I was attacked and publicly crucified, and that was followed by this article in the Denver Post a year ago, which was a very thinly veiled personal attack aimed squarely at me.  From my perspective, it appeared that the ultimate reward for making an effort to communicate with those that I serve was to be publicly called out as a liar on the pages of the biggest printed media outlet in this state. I've got to be honest -- that was a devastating blow to take.  
     In addition to being accused of lying, what might have been even more brutal was to be accused of not being an angler.  This is a common tactic used by some people when there are no factual arguments to be made, and it's not just directed at me.  There have been many instances around the state in which my coworkers have been branded as "non-anglers".  The purpose of such claims is to cast us as some kind of entity which is "apart" and does not act in the best interest of recreational anglers because we apparently have no idea what recreational anglers want.  These claims have no basis in any kind of factual information.  It is simply impossible to land in this job without being an avid lifelong angler.  I don't even know why someone would want this job if that wasn't the case. It's not particularly easy, and it doesn't pay as well as countless other professional pursuits. However, if fish are the most fascinating creatures in the world to you and you've always been enthralled with their pursuit, it's the best job you could possibly have.
     So enough rambling. People who desire to be personal enemies to me have clearly identified themselves, and it's time to move on. But if I remain silent, I allow them the last word in defining who I am to the world at large.  I realize that these people are a "vocal minority" and many others have reached out to me to express that they find this blog to be valuable. So it's for these folks that I choose to continue with it.  So on that note, here are some of my favorite angling memories from 2015.

     In June, our family's schedules resulted in my youngest son Ben and I having the house to ourselves for a few days. I decided to make it a fishing odyssey.  One evening we were up at Meadow Creek Reservoir to try to catch the evening bite. I'll never forget the sound of Ben's voice as he exclaimed, "what the heck?!?!" as he hooked a sizeable brookie on his kastmaster. He was sure he was snagged for a second, until he realized it was moving. He proceeded to outfish me that evening, for the first time ever.
     The next day, we headed out on an overnight backpack. We take family backpack trips every summmer, but this was the first time that just Ben and I had set out. We headed for a promising lake in hopes of dining on brookies cooked over the fire. It was early in the summer, and the trail was not easy, with downed trees, some snowbanks, and lots of mud in the shady areas. However, we were rewarded with hungry, aggressive fish and we did enjoy that brookie supper. In the morning Ben was excited to get back out there and catch a few more before we packed up. Once again, he caught more fish than me on the trip.

                                        

     In August, we took the best family backpack trip we've ever had. It was one of the last weekends of summer and in the scramble leading up to the school year there were many things on the to-do list. Instead, we scrapped it all and hit the trail for a couple of nights. It was one of the most beautiful hikes we've done. On the second day we headed for one of my all-time favorite lakes, off trail and packed with aggressive cutthroats. This lake doesn't get stocked, and sustains a fantastic fishery solely through natural reproduction. The boys experienced their first-ever "double," pictured below, where they both had fish on at the same time. I won't forget that moment.  




     My sons are finally at the age where they've got some good stamina and enough physical ability that they can now get deeper into the woods than they've gone before, and I'm very excited about our adventures in the coming years.
     
     In September, I took a day and bushwacked in to my favorite low-elevation rugged canyon creek. The fishing is fantastic for a mix of browns and wild rainbows ranging from 8 to 14 inches. Ironically, on this particular day the rainbows were taking nymphs and the browns were all about the dries. It never takes long to get into "the zone" on this creek, and for a few hours the whole rest of the world just melts away. I don't seem to need days like that as often as I used to, but I'm always amazed at how much my batteries recharge when I take the time to do it.

     Over Christmas break, despite the brutal cold we dragged my Dad out and we did a little ice fishing on Willow Creek Reservoir. Although we grew up fishing a lot, southern Kansas never offered much in the way of ice fishing opportunities, and it was my dad's first time ever on the ice. We barely lasted an hour out there because the wind came up, but at least we got out there, on a day that seemed too cold to do anything.



     For me, the enjoyment of fishing has always been about the place just as much as it is about the fish. And increasingly, in the past few years, it's been about appreciating those places with my sons. So with luck I'm looking forward to a 2016 filled with more such memories, and here's hoping that everyone is able to enjoy such special times. 
     I'll get back to talking about fish populations with my next post. I would like to get some feedback on what topics folks would like to read about in 2016. So please don't hesitate to make comments here, or drop me an email at jon.ewert@state.co.us. Thanks!

     

Monday, March 2, 2015

Still alive . . .

     Howdy folks, sorry for the extended break. Hope 2015 finds you well. I still intend to keep this going - just probably not at a weekly pace. For now, check out my updated report on the Colorado River at Parshall, posted here:

http://cpw.state.co.us/Documents/Fishing/FisheryWaterSummaries/Summaries/Northwest/ColoradoRivernearParshall.pdf

     So take a look at that. Hopefully it will stimulate some discussion. If you have any thoughts/comments/questions, either post them here or shoot me an email at jon.ewert@state.co.us. Hope to hear from you.

Monday, March 3, 2014

State of the Fish

     I have scheduled my annual "State of the Fish" meetings for this month. On Tuesday the 18th we'll be at the Frisco library, in the Buffalo Mountain Room, at 6:30. On Wednesday the 19th we'll be at the Granby public library, also at 6:30. These meetings will follow an open format, and we'll talk about whatever waters folks are interested in talking about. There are a few regulation items I'd like to discuss, if anyone in attendance is interested:

  • Grand Lake lake trout
  • Granby lake trout
  • Dillon char
     I hope to see lots of folks come out for these. I'll stick around for as long as anyone wants to hang out and discuss things.

     Aside from that I'm having trouble coming up with topics for posting right now. I need some ideas from you folks. 

     February was a ridiculously warm month, and these reservoirs are not going to make it to April 1 with the ice on if this weather keeps up. Things are changing fast. It's looking like the earliest ice-out I've seen since I've been around here. I wish that wasn't the case because I'm not going to be ready for it before April 1.

     I'm headed up to Laramie for our annual American Fisheries Society meeting/conference, which is always a great experience, with lots of information being exchanged and new ideas being born.

     



Friday, February 14, 2014

Scrappy Sculpin and the Sad, Sad Snake

     Thought I'd share some info on a couple different topics. First, one of my favorite fish species of all time - mottled sculpin, Cottus bairdi. I previously posted some pics of a recently-consumed sculpin coming out of the throat of a brown, down at State Bridge. We are lucky to have some areas of very dense sculpin populations, where they are the most numerous species of fish. Here's my favorite picture of a sculpin, taken by my Forest Service counterpart Corey Lewellen:


     They've got the best pectoral fins out there.
     One reason it occurred to me to discuss our sculpin populations is the appearance of this recent news item:

http://news.yahoo.com/big-headed-fish-species-discovered-idaho-montana-rivers-201333579.html

     It is always interesting when a new species is described, and the news media picks up on it to say that it has been "discovered." It makes it sound as if no human has ever seen the fish before. The reality is, anglers and biologists have likely handled these fish untold thousands of times; it's just that this is the first time that they were examined genetically. I'm certain that something very similar would happen if we closely examined our sculpin species in Colorado. We would probably have at least one new named subspecies or species. Right now, we've got two that we know about; paiute sculpin (Cottus beldingi) and mottled sculpin (Cottus bairdi). Some of the sculpin from waters in Grand County have been keyed out as paiutes, which is only possible in a lab. The bottom line is, we don't know the exact distribution of the two species, if they overlap, if there is hybridization, or if there is at least another subspecies that is unrecognized. There has been talk that the sculpin in the Eagle River may constitute their own subspecies. For simplicity's sake, what is important is that they're a native fish, and on the upper Colorado we've always referred to all of them as mottled sculpin.
     We've found some interesting patterns in their distribution at the headwaters of the Colorado River. Below is a map depicting a simplified version of the distribution pattern:

     The green lines I've drawn here represent streams that have sculpin populations, and the red lines represent streams where sculpin are absent.  We have found that almost without exception, we have dense populations of sculpin upstream of every impoundment in Grand County, and the absence of sculpin below every impoundment. It is astounding how consistent this pattern is. Last September I was able to add the Muddy Creek watershed to this map, after doing some sampling on private land upstream of Wolford Reservoir and finding high numbers of sculpin there. There are zero sculpin in Muddy Creek below Wolford. Williams Fork, Windy Gap, Willow Creek, and Granby - all these reservoirs have dense sculpin populations upstream and no sculpin downstream.
     On the Fraser River in the town of Granby, sculpin are by far the most numerous fish species. In 2012, in a 600-foot reach of river there, we collected 1,279 sculpin, and they constituted 83% of the fish we captured. That yielded a population estimate of at least 20,000 fish per mile. Moving downstream past Windy Gap, to the mainstem of the Colorado River, at the Hitchin' Post Bridge, we have searched the riffles there every year for sculpin and found zero. This is only about four miles from the site on the Fraser in Granby, and the species that is most plentiful in the first site is completely absent from the second site. 
     Sculpin reappear in the Colorado River at some point below the Blue River confluence. At Pumphouse, they are very dense again, and are again the most numerous fish species present. 
     We don't know the precise reasons for this distribution pattern, but we would like to. It's not an overstatement to say that there has to be a massive ecological shift that takes place over short geographical distances to produce such a contrast. 
     On a positive note, there is some movement toward mitigation work taking place on the Colorado as part of ongoing negotiations with the water providers. It's looking likely that Windy Gap will be re-engineered somehow to become an off-channel reservoir, and that a bypass will be built. Also it looks like there may be a pool of money that becomes available to to a lot of physical habitat work in the river from Windy Gap on down. We'll see.

     I gave an update recently at a meeting of the Snake River Watershed Task Force in Keystone. If you're not familiar with the Snake River, it's an interesting place. It's got by far the most polluted water of any stream in the area. A lot of the metals pollution comes from the Peru Creek drainage, where there are old mines releasing acidic water laden with high concentrations of metals that are lethal to fish. If you're at all interested in water chemistry, Peru Creek is a fascinating place. You can walk up the stream and the bed of it is an ever-changing rainbow of colors, based on which metal is precipitating out of the water in that particular reach. There are white sections, red sections, greens, blues - lots of different shades.
     Below is a map, courtesy of my USGS colleague Andrew Todd, depicting where in the Snake River watershed we have fish living in streams and where we have no fish at all. The blue sections are where there are fish, and red is where there are none:

     Below Peru Creek, the only reason that any fish can live in the Snake River at all is the dilution that is provided by the North Fork, coming down off of Loveland Pass. The amount of relatively clean water coming from that drainage dilutes the metals pollution just enough to allow some trout to persist below that point. However, it's not exactly a high-quality trout population.
     We have a survey site, right along the base of Keystone, that we sample every year to check on the status of the fish population and it tells some interesting stories. The brook trout numbers tell us the most, because those fish  are never stocked or manipulated in any way -- if they're there, they got there on their own. Here is the population estimate for brook trout on that reach going back to 2007:


     These numbers are estimates of the total number of brook trout inhabiting the 500+ foot reach that we survey. It's not extrapolated out to fish per mile or anything. So you can see, this is a distressed fish population and this river teeters on the edge of even being suitable for fish at all. The reason why there are two samples in 2007 is that there was a flash flood from a cloudburst that hit the Peru Creek basin in late July of that year. We had already surveyed the site before the flood. We had reports from the public that there had been a fish kill during the flood. We went back a month after the flood and electrofished again, and saw that the flood had wiped out the brook trout population, and in fact it wasn't until three years later, in 2010, that we even saw brook trout there again. And, as you can see, the brook trout population has never returned to pre-2007 flood levels. 
     Keystone Resort purchases and stocks rainbow trout annually in this reach of river. They buy them at a large size, and they do provide entertaining fishing for the tourists. I wondered if we get any holdovers at all from year to year among those rainbows, and so in 2008 I started adipose-clipping all the rainbows that we handled in the survey section. This way, we can see whether or not any of those stocked rainbows survive a winter there. Below are those results:
r
     So, out of the 46 fish that we marked in 2008, we captured 5 in 2009, for 11% survival, and so on. 2012 and 2013 have been particularly rough in this respect. For this data, fish emigrating out of the reach counts the same as mortality. Whichever happens, it's obviously not very hospitable there.
     The good news about the Snake River is that after a couple of decades of effort and attention, there is a broad coalition of entities (EPA, US Forest Service, USGS, Summit County, etc.,) starting to clean up the mines of Peru Creek.  It has taken a huge amount of concentrated effort and searching for funding. There is real momentum now and in 2013 quite a bit of underground work was done to figure out what it's going to take to clean up some of the most polluted water. So, hopefully in future years we'll see those metals concentrations drop and a healthier fishery develop.



Thursday, January 30, 2014

Tough times in Parshall

     I've done some processing of the data that I collected on the Parshall reach of river and it's not great news. This is the reach of river that we have a long-running historic data set for, going back to 1981. I survey two miles of river there every September, starting in the split channels upstream from the Parshall Hole, and continuing on downstream into the BLM Sunset parcel. We end it at the big irrigation diversion there. This reach of river has really been struggling the past several years and I can't put my finger on the exact reason why. Here are the population estimates in fish per mile greater than 6" (rainbows and browns combined) going back to 2000:

     Here are the rainbow population estimates:


     2012 was the year that we finally saw good success with the HXC's. Rainbow numbers came down in 2013 but I'm optimistic that the overall trend will be upward in the coming years. A quick comparison of the two figures shows that rainbows still make up only approximately 4% of the total trout population of fish greater than 6". Anglers have been reporting better catches of rainbows since 2012, but you have to remember that rainbows are approximately 10 times more vulnerable to being caught than browns are. So you can have a population that is 90% browns and 10% rainbows, and because of the greater catchability of rainbows, an angler may perceive that there are equal numbers of the two based on his catch rates. 
     Here are the density estimates of "quality" browns (over 14"), by surface acre of river. To me, this is the most disturbing statistic:

     As you can see, this is the lowest estimate we've had in recent history for fish >14". This reach of river has really been struggling in this regard. At this point it's barely maintaining the minimum standard for a gold medal-designated fishery. In 2010, we captured more than twice as many browns over 14" on that reach of river than we did in 2013. The gold medal standard is at least 12 fish per acre over 14", and at least 60 lbs./acre of total trout biomass. Speaking of biomass, here are the estimates from recent years:

     This is the only parameter that we saw an increase in 2013 - albeit a small one at that, and well within the margin of error for these estimates.
     So when I've got data like this that shows a lot of doom and gloom, one of the first things I do is ask myself if there is some way that the data could be wrong, and that it is not reflecting true trends in the population. The biggest reason for it to be totally wrong would be if during some years there is some large-scale movement of fish out of the reach, and in some years the opposite. But we know that for the most part browns don't move large distances. Most movement studies that have been done with trout in rivers show that a very small percentage of fish move large distances, but most fish live their whole lives over a relatively small reach of river - a mile or a few. The way that I control for timing of movements is by running this survey as close to the same dates as possible every year - right around the third week of September. The reason why it works best at this time is that the water has cooled enough that it's not overly stressful on the fish, and it's still early enough that major spawning movements and concentrations are not in full swing yet. 
   The other thing that makes me think these trends are real is best illustrated in the biomass estimates. The trend was downward every year from 2007 to 2012. If there was a large amount of error in this estimate, there would be a lot more variation - it would bounce around more. 
     I'm interested in hearing from folks who fish the Kemp-Breeze a lot, to know if their angling experiences match what I'm seeing in this data. Are you catching fewer browns over 14" than you did just a few years ago? Has the average size of fish that you are catching become smaller? 
     So let's assume this is all real, and speculate as to the reasons. We know there is functionally no harvest taking place there, because it's a catch-and-release area. There is a ton of fishing pressure, but there always has been. I definitely don't believe that there was more pressure there in 2013 than there was three, or five, or ten years ago. This reach of river doesn't have extreme temperature problems because it's right below the Williams Fork confluence, which cools it down during the hottest portion of the summer.
     One thing that always lurks in the back of my mind is the impact of anchor ice in certain winters. Last winter was a great example, when we had weeks of brutal cold, around 30 below every night. During times like that, you can go look at the riffles right around the Parshall Hole and see the anchor ice covering the cobble. That has to have some form of impact. It's difficult to get an idea of how flow varies from year to year in the dead of winter, because the flow gauges in the area are off for the season. 
     I also wonder if it's a forage issue. We know that since the early '80's, we've lost the giant stonefly hatch that used to be prolific there. That species isn't the only one that's gone - our studies have found a whole list of invertebrate species that have disappeared from this reach of river. But these extirpations happened gradually over the past 30 years - it's reasonably safe to say that they had already occurred at the times in the previous decade when biomass was twice what it is now and when densities of quality trout were far higher. Also, there is evidence that does not support the forage limitation theory: the fact that body condition of the fish is consistently good. Not spectacular, like we have seen at Radium, but good. 
     It could be a habitat degradation issue. There are sections of river that are utterly featureless, and at 150 CFS on these sections the river is 200 feet wide, ankle deep, and contains nearly zero fish. Whether or not the physical habitat has slowly been degrading over time is a question that I don't have an answer for. 
     Anyway, I'm interested in hearing your thoughts on this, so let me know if you've got any opinions. Thanks.