Sunday, April 14, 2013

Dillon, part 2: the char experiment

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

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

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

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

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

7 comments:

  1. Jon, Thanks for the info on these fish. Also good talk a few weeks ago in Silverthorne.

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    1. Jon, Great info! Can you tell me anything about depth of these guys? When you mean deep.... 40ft 80ft 100ft? If you don't have much info on the Dillon char how about the ones found in Canada or how deep are the Mysis shrimp that they are feeding on? I am trying some new techniques with fishing deep on a fly rod and arctic char might be a good challenge. Thanks

      Bennett Colvin

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    2. Thanks Mark. Bennett, I really don't have anything more specific than what I gave you on depth habits. You have to go out and find them.

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  2. Jon, Is there any chance you are going to be doing a survey of Dillon any time soon?

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    1. James, I have been running nets on Dillon only every other year - the even-numbered years. So I don't have any plans to do it this year. There are other folks (like Devin Olsen, who I mentioned above) doing much more intensive work right now, so there's not a lot of need for me to be gathering more information - they're doing it as part of the current research project.

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  3. Thanks for this article, Jon. I have always wondered how this species has been fairing,

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  4. Thanks for the great information and article Jon!

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