Sunday, May 19, 2013

Waiting for the reservoirs to fill

     We've been in a little bit of a holding pattern for the past week. It's time to start my annual spring reservoir netting surveys, but I decided to delay these a little bit in order to run the nets at a time when the reservoir elevations are at least a little closer to what they have been in the past. If the reservoir elevations are extremely different, it will be harder to draw solid conclusions when I compare this year's data with past years. But we'll get started this week, beginning with Wolford. We've been spending our time over the past week mostly running pike traps in Wolford and Green Mountain.
     So, I'll answer a few recent questions. From an anonymous poster on another website:

"Why can folks put feeders on the river in close proximatey (sic) to public waters?"

     Well, the real answer to this question is because it has never been outlawed. I can think of many reasons to do so. I personally don't agree with this practice at all. However, to propose such a regulation would invite a tussle of political maneuvering the likes of which I, as a lowly field biologist, have no desire to engage in. I could certainly provide some very solid arguments for why this practice is detrimental to the wildlife of this state in the big picture and the long run. But the impetus for passing such a regulation would have to come from an organized group of sportsmen from outside this agency. Unfortunately, our sportsmen are not all that organized, and at times that really costs the wildlife of this state. Not trying to be controversial or un-politically correct here, just calling it as I see it, personally.

 "Why then cannot I use corn or such to shoot deer or ducks over? "

     Because enough people thought it was unethical to do this, and passed regulations and/or statutes to outlaw this practice. But the analogy you're drawing here is more similar to chumming fish, which is also illegal. But where do you draw the line between feeding a free-ranging fish population in a river and chumming fish? Therein lies the rub.

"Are there the same 2 week regulations?" 

     I don't understand this question.

"Why is this allowed at all...shooting food into the river? Do they feed what they want? re they regulated as to what feed they can use?" 

     Again, it's allowed because it's never been disallowed. There are no regulations regarding what type of fish feed people can throw into a river. I'd be glad to discuss this topic further, if anyone is interested in doing so. Please comment.

Here's another:

"I read your comments abouth the Blue River in the Denver Post. You said the aquatic life in the river is just not up to supporting a quality fishery and that the lower section, down towards Green Mountain is especially barron. My observation of the Blue is that there are long sections of river that are just gravel and have no structure. I would think dumping a bunch of good sized rocks in those sections would increase insects and the fish they support. I see alot of the same featurelss water on the Platt downstream of Deckers. Are there any plans for streambed impovements on these rivers. It seems to me that improving what we already have access to is just as important as getting more access. "
     Thanks for the comment Homeboy. Please use your real name. This is a good question. I don't disagree that some of the sections of the Blue downstream from Silverthorne have poor habitat quality. I'm sure that those sections would benefit from habitat improvements, to a certain extent. I am not aware of any immediate plans to do habitat work on these sections, but it certainly may happen in the future.
     However, I don't believe that physical habitat quality is the limiting factor on the trout population on the Blue. I have lots of good data that shows that slow growth is a consistent trait of this trout population, in multiple locations on the river. Slow growth is not caused by a lack of physical structure. It's caused by a lack of food availability. You're suggesting that working on the physical habitat would increase insect densities. The focus of a physical habitat project in a river is to improve the trout habitat, not necessarily to improve insect production. Those are two different things. Cobble riffles are generally the best habitat for insect production (at least, the kind of insects that are desirable for trout and us), and I can show you plenty of featureless, cobble riffles on the Blue that are just fine insect habitat (but poor trout habitat). But, that doesn't change the fact that the insects are sparse there. What I'm getting at is that I think it's more of a nutrient/chemical issue of some kind than it is a physical habitat issue. 
     On the Colorado, there are many places where the trout habitat is awful- the river is far too wide for the amount of water in it and there are vast, featureless cobble riffles. There is a far higher density of both insects and trout - and far better growth rates in the trout, even though the habitat is very poor. It's an interesting comparison to the Blue.
     Another important thing to think about, is that there are some sections of the Blue - the one that comes to mind is the section from Boulder Creek down to Columbine Landing and the Highway 9 bridge - where there is no shortage of good, quality trout habitat. It's got plenty of deep runs and pools that are difficult to wade at any flow. There is a ton of large object cover. And the trout population there is really no better off than the population in the sections with poorer habitat. The density is a bit higher as a result of the better structure, but the quality of the trout themselves is no better. They still grow very slowly, and do not often reach very large sizes. 
     I'm not saying that there is no place for doing some in-channel work on certain sections of the Blue. I just think that if we do, we need to be very realistic about what the potential benefits of that work would be. It's not going to magically produce a high density of quality-sized trout. It would produce a higher density of skinny, 8-10-inch browns.
     I've had a lot of discussions with various folks about how we could go about directly addressing the productivity issue on the Blue, and we've got some ideas floating around. They're pretty preliminary though.

Now - I covered two specific topics in this post. Did I contradict myself between the two topics? You tell me.

1 comment:

  1. Sorry Jon, my name is Alan Berry (homeboy). There was an observation on CFF that the biomass in the reservoir was better with a sewage plant upstream. Maybe we need a "do #2 in the Blue" ad campaign and some streambed improvement. ;O) Thanks for your thoughtful response to my question.