Tuesday, March 1, 2016

Green Mountain timeout, part 2.

So that was the good news. Now the bad news. We've got problems at Green Mountain. They had already started by the time I got here in 2007, with an explosion of the gill lice parasite in the kokanee salmon population. From that time onward, the reliability of the kokanee run took a nosedive and has never recovered. Green Mountain used to produce a good spawning run in the Blue River as well as reliable ice fishing for silver kokes. Those opportunities disappeared after the gill lice showed up.  As far as I can tell, a few folks still get into some fish by snagging during the spawn or ice fishing for silvers, but it's extremely spotty and unpredictable.
       Because they originated in the Pacific, the gill lice that we have infect both kokanee and rainbows (also from the Pacific). They do not infect browns or lake trout. The rainbows at Green Mountain are also heavily infected and have been for years, with no reduction in infection apparent over time. There is no known mechanism of control of gill lice in a water body this size. Except for one. 
     This is an obligate parasite - meaning, it won't survive if it can't find its specific host species, in this case rainbows and kokanee. The only known biological way to reduce prevalence of the parasite is to deprive it of its host. This is one of the three reasons that, for the first time in the history of the reservoir, we are not stocking Green Mountain with any fish in 2016.
     The other problem we've got at Green Mountain is an illegal introduction of northern pike. I received some word-of-mouth reports of pike being caught beginning in '08 or so, but no confirmation with photos or any carcasses. I finally picked one up in my standard gillnet surveys in 2012.  Then I got four in 2013, one more in 2014, and in 2015 I picked up 17. That's not quite as bad as it sounds, because in 2015 I increased my gillnet effort from 24 net sets to 40. So in terms of gillnet hours, pike capture went from 0.01 fish per hour to 0.07 fish per hour. So still a low catch rate indicating a small population, but they were all the same size (22-25 inches), indicating that they are all from the same year class, born in the lake around 2012. 
     When Green Mountain spills, the volume of water going over the spillway can be big. 2015 wasn't a particularly big water year, and it spilled for 15 days at an average of 513 CFS. In 2011, which was a huge water year, it spilled for 27 days at an average of 1,141 CFS. So if pike take off in GM, we've got a huge risk of the lake dumping a lot of them into the Blue and Colorado Rivers. We do a lot of survey work downstream of GM, and we have not seen pike establish themselves at this point. 
     What's so frustrating about this is that whoever takes it upon themselves to spread fish around is probably unaware of the implications of tying these waters to the Endangered Fish Recovery Program. We have a great luxury here at the head of the basin in that we can manage these waters with recreational opportunity as the top priority. This is a luxury that we should never, ever take for granted. If the species that are problematic to the Recovery Program - northern pike, yellow perch, walleye, smallmouth - continue to turn up in these waters, it is probably only a matter of time before it is proven that fish from one or more of these reservoirs are finding their way all the way down to Rifle and causing problems in the recovery area. At that point, managing these fisheries to maximize recreational opportunity immediately becomes the second priority, and that luxury that we've enjoyed all this time disappears indefinitely, possibly permanently. All options are on the table then, including rotenone treatment of large reservoirs and closing large bodies of water to fishing.
     I know I'm preaching to the choir here.  I've communicated this message before many times, and no one who would bucket stock fish would ever take the time to read this. So this is the second reason we're not stocking any fish into Green Mountain this year. We're not going to turn that lake into yet another pike feedlot. We've got plenty of them around, and it's a ridiculously expensive way to manage a fishery. 
     Here's the little bit of good news within this piece of bad news: we're implementing a northern pike angler harvest incentive of $20 at GM. If you catch a pike there, you can take it to Heeney Marina and they'll give you a twenty dollar bill. We have got to get on top of this as quickly as we can, and enlisting the help of anglers is the best way to do it.  So I'm hoping that whatever angler traffic is lost due to the lack of stocking, is replaced by folks going after pike.
     The third reason we're not stocking fish is that we've got some production issues in the hatchery system. I rely heavily on our Glenwood Springs hatchery for a lot of my plants, and last year Glenwood came down with a disease called Bacterial Kidney Disease. It's a long story, but the point is that we can't stock fish that have been exposed to this disease, and Glenwood had to be completely depopulated and disinfected last year. So there is a general shortage of fish on the west slope as the other hatcheries try to make up for the fish that Glenwood will not have in 2016. One of the results is that I have a smaller allocation of rainbows than normal. If I cut one major reservoir (Green Mountain) out of my schedule, I am able to maintain catchable numbers at the other large waters in my area.
     One benefit taking a timeout from stocking is that this will serve as a large-scale lake trout management experiment. A couple messages that I get on a regular basis from the lake trout angling community are an almost universal lack of support for kokanee in Colorado, and and the assertion that we can have perfectly good trophy lake trout fisheries based on a sucker prey base alone. These two positions are totally misguided - and quite possibly tragic for the future of trophy lakers in this state - but we've seen over and over again that it doesn't matter how many times we try to communicate this.  Here is our golden opportunity to test these theories.  The proof will be in the pudding, and we'll see how this trophy lake trout fishery fares when both kokanee and rainbows disappear from the prey base.


  1. A couple of quick questions. How many years would you have to maintain the "no stocking" regimen in order to eliminate the gill lice? Is it feasible to stock Brown trout, ie do we have the hatchery resources? Do Rainbow trout move into Green Mountain from the Blue River and if so is there a way to prevent or minimize it? I'm assuming you will continue to stock the Blue.

  2. Keith, one positive aspect of Green Mountain is that it's got a relatively robust wild brown trout population, and I don't see a need to supplement that. I do not have a specific plan for how many years of no stocking that we're going to pursue. It will be a year-by-year decision. We will monitor both the gill lice and the pike situations to help guide that decision. I'm not optimistic that we can actually eliminate gill lice from the reservoir - the goal is to knock them back to a lower level of prevalence so that we can at least see a kokanee run develop again. There's a big difference between fish with 1-5 gill lice visible vs. having their gill just packed full, which is what we see now. And yes, stocking plans will remain the same for the Blue - there's a gap there though, because we don't stock anything downstream of the Silverthorne city limits - just in town.

  3. Jon, Thanks for this bog, As an avid fishernan for trophy lake trout since 1992, I promise you those lakers will adapt, I have caught many lakers at Gm that were spitting out suckers. My best strategy at GM is to locate big fish on shalow muddy flats from 10 to 30 and pck them off the bottom as they are cruising slowly to ambush suckers. On top of being sucker eaters at GM, the biggest fish I caught out of GM last year was 34 inches, and it had a 13" lake trout in its mouth. With so many young and small lakers in GM. Those big lakers will also benefit the fishery by helping control the over population of the samller lake trout.
    Kokanne salmon are high in calories but those lakers have to work harder to get then by staying under the schools, and then shooting up from down below to ambush them. Out in the deep, kokanne move fast, and lakers can only get them buy chasing hard as the kokanne scurry. The large lake trout at green mountian like the shallow mud flasts were they can hang out, cruise and ambush sucker fish. The big lakers in GM will be the most beneficial fish for the fishery. Your nets will see a substantial decline in suckers, and the body condition of the large lake trout probably wont increase, and it may slightly decrease to look more like a Granby mac, but those lakers big lakers will sustain and remain. They wont die off due to lack of kokanne and rainbows. They will find away and continue to provide one of the best ice fishing opportunities for lake trout in the whole state. Randy Ford

  4. Jon,

    Correct me if I'm wrong, but it sounds like we don't know if there is a sustainable sucker population in GM to solely feed such a large laker population. That's beside that fact that the newly introduced northern pike will compete with the lake trout for the same suckers. Both of these species are opportunistic feeders, but it sounds like this decision could devastate this fishery. It appears you don't have a choice due to the gill lice, but is there a "plan B" in the event the this plan fails.

    Ryan Dougherty

    1. Hi Ryan, thanks for the comment. GM is actually one of our lakes that has a very high biomass of suckers. In the last four years of my gillnet surveys, suckers have made up 65, 57, 70, and 61 percent of the total fish caught. Putting it another way, for every one lake trout > 24", in 2012 we caught 16 suckers, in 2013 we caught 19, in 2014 we caught 23, and in 2015 we caught 9. So one way this could be successful (as Randy Ford has pointed out) is that the large lake trout are forced to eat suckers because that's the only prey available, driving sucker densities down. That would theoretically result in higher densities of small invertebrates and zooplankton in the reservoir, making it ultimately more productive for rainbows and kokanee in the future. But we have to give them the chance to do that. If you continue feeding lake trout with stocked rainbows and kokanee, they will always preferentially feed on those two species before resorting to suckers - that has been proven in many studies over and over. That is the reason why we do not have any lakes that we can point to where we have achieved sucker control with lake trout alone - because all of those lakes continue to have high densities of rainbows stocked. Suckers do not replace kokanee and rainbows in terms of quality of prey - they are long-lived and slow-growing, and their flesh contains far fewer calories. Also, regarding pike vs. lake trout competition: I do not believe there are enough pike in the reservoir currently to make much of a competitive impact with the lake trout. That's why it's so important to enlist the help of the anglers right away in getting on top of this pike invasion before it does turn into that.

  5. This comment has been removed by the author.

  6. Bad news for sure, the Gill lice have decimated Kokanee populations at several reservoirs. Getting rid of the Host hopefully will eventually help the situation.
    Although being natural in the environment it is still a possibility the lice will come back as fish get stressed they are more subject to getting infected.

    The last paragraph of your Article is very concerning.

    You believe that universally Lake Trout anglers do not support Kokanee fisheries.
    I could write a book about how wrong this is…. Most Lake Trout anglers also love to catch Kokanee.
    Personally I was a Kokanee fisherman long before I fished for Lake Trout.
    My family and friends would catch them all summer trolling and Can them to eat along with catching and snagging them where allowed to smoke and collect eggs for bait.

    Of course we support Kokanee...

    We may be tired of always hearing from the fish managers that the Kokanee's woes are the Lake Trout's fault when they know there are much greater problems facing them.
    Gill lice devastating populations at GM, Williams Fork, Eleven mile and now Blue Mesa.
    A natural Algae bloom and die off at Blue Mesa.
    Starving Kokanee at Dillon and Granby due to Mysis depleting there source of food and leaving the water depleted of the basic nutrients they need to thrive.
    None of these problems have any thing to do with Lake Trout yet they are constantly looking at ways to discredit and try to downgrade our great Lake Trout fisheries.

    The proof in the pudding as Jon puts in the last sentence that we will see how Lake Trout do without stocked Rainbows or Kokanee is going to be an interesting experiment.
    I'm guessing do to the basic productivity of the lake with a large population of Smaller LAke Trout and Suckers along with overall low populations Large Lake Trout we won't see a dramatic change.
    Steve Penley.

  7. Jon instead of totally devastating the seasonal open water rainbow Shore fishery, maybe at peak usage times it would be great if you could stock a few larger Rainbows that would fair better around predators for the benefit of the many shore Anglers.

  8. Jon can you provide any insights on the locations where the pike were caught? Best way to target the, from shore ? Thanks

    1. Mark, the shallow coves in the northeast part of the lake are where we picked up almost all of them. A boat probably isn't necessary, but waders or a float tube would be good. Before the lake is full, there are big areas in those coves less than 10 feet deep, and they seem to cruise anywhere in there. Go get 'em.

  9. With all the ongoing problems with Hatcheries and Gill lice, now would sure be a great time to invest in self sustaining species.
    Lake Whitefish would be a great addition to Granby.