Sunday, March 3, 2013

State of the fish

     Hi all, just wanted to let you know that we are going to host a couple meetings that I'm calling "State of the Fish" meetings. One in Granby at the public library on Wednesday, March 13, at 6:30 PM. We'll do another one in Silverthorne on Monday, March 18, at the public library also at 6:30 PM. 
     I'd like to run these meetings with a "data workshop" format. That is, I won't necessarily have a canned power point presentation to show people. Rather, I'd like to start the meeting by asking folks in attendance to call out the name of a water body. Then, I'll walk everyone through data, stocking records, future plans, etc. regarding that body of water. It will be important for this to be a collaborative meeting, with a lot of give and take. Hopefully the flow of information will be in both directions, as the purpose of these meetings is just as much for me to gather the anglers' perspectives on these waters, as for me to give folks information. So, I hope folks can make it out for that. 
     Meanwhile, I've got four new reports up on the web page, check these out and chime in with any comments or questions:

Now, From Bennett - 
Hi John thanks for the reply on the Tiger Muskie. I am really hoping that you plan comes to fruition. As far as the lake trout are concerned in Grandby is what your seeing a cyclic problem? Every few/many years we can expect an imbalance? Or is there a greater concern such as what you are seeing at Blue Mesa and a serious management approach needs to be taken. Also, in Colorado do we have any good self sustaining lake trout lakes or do all of them need to be fed with kokanee or rainbows? 

 Bennett, the biggest difference between Blue and Granby is the presence of mysis in Granby. When conditions are unfavorable for kokanee in Granby, it's not just due to a simple overabundance of predators - it's also due to an overabundance of COMPETITORS (in the form of mysis, preying on the same zooplankton that kokanee prefer) who happen to do well in the same conditions that favor lake trout reproduction. Once all three species (mysis, lake trout, kokanee) were present at Granby, it's always been on a cycle where conditions swing wildly back and forth. When the kokanee can't maintain themselves, a big predator such as lake trout is basically a luxury that the lake can't afford - that is, they have no forage base. We're going into a period now, though, that is going to be unfavorable to both lake trout reproduction and mysis densities. With the way that Granby has been dropping through the winter, there will be very few or no lake trout born in the lake in 2013, because the eggs are getting dried out or frozen as we speak. So, it's like a pendulum that swings back and forth in response to drought/wet weather cycles. One big drawback is that we really can't depend on Granby for eggs to stock other waters any more - if we get them, that's great, but we can't count on them. 
     When you ask about "self sustaining" lake trout lakes, I think you're using a little bit different definition than normal. We usually use that term when we mean that a species of fish maintains itself with no stocking to maintain its numbers over time. In that sense, pretty much all our lake trout lakes are self-sustaining -- that is, we don't stock them. They do a good job of reproducing on their own. But what I think you're asking is, are there any lakes that produce their own forage for lake trout, without any stocking to augment their prey base.  I'm not aware of any. Granby may be the closest, if you just consider the life stage of lake trout up to 21-24 inches. Prior to reaching that size, they do really well feeding on mysis. But there is always some predation of fingerling rainbows, age-1 kokanee, etc. So that's close to a self-sustaining system in the sense that you're talking about. Then they make the prey switch and start eating stocked fish. That is one reason why kokanee are such an important link in the chain - they are far cheaper to maintain as a forage base for lake trout than stocked rainbows are.

     Again, I hope to see folks come out to the State of the Fish meetings. See you there.

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