tb – I want to say I remember talking to some guys who fished Greens Valley at the Jam a couple years ago. Might have been pcray’s group? I think they said they caught Brookies in it, but I’m not 100% certain. Pat – Was that you guys?
Yeah, that was us. And we did NOT catch brookies in it. Plenty of holding water, just didn't move a fish. We fished upstream from where Laurel comes in. We did hit Laurel for a minute or two and caught fish there.
Now that the new mapping thing is out, and shows the stream class, it looks like Greens Valley where we fished it is class D. I won't claim there were zero fish, but I'm guessing not many, and combined with a severe rhodo tunnel effect, we just didn't catch them. But if we had gone downstream, it may have been better in terms of # of fish. We went the wrong way.
I suspect you guys are referring to some combination of geology and lack of bug life when you say a stream “looks” infertile, but can you elaborate on that? What do you “look” for? What leads you to suspect that based on the stream’s “look”?
Obviously "orange" is a bad sign, lol. But aside from AMD, many of the poor streams I've fished are acidic from a combination of acid rain and a lack of buffering, and that's the true reason for the poorness. You will find a lack of bug life, not even all the little dancing midges and so forth that you see elsewhere on the water. It can be midsummer but the stream gives you that January "dead" feel. There's not even a biologic film on the rocks.
As for fertility, note that pretty much all streams which are acidic (for acid rain reasons) are also infertile. Because fertility and buffering go together. That said, not all infertile streams are overly acidic. Infertile streams which are not too acidic do tend to hold fish, and sometimes fish very well. Structure is the #1 factor regarding size and number of fish in these streams. But given the same structure, fish will tend to run smaller on less fertile waters.
Fertility can often be judged by common sense as well as water color. Infertile streams often have that absolutely, jaw droppingly crystal clear water, where every color shade on every rock even at 3 or 4 ft deep can be distinguished. I think we instinctively notice rock types too, even if we don't know the real geology.
If it happens to be class A, the class A list gives T_Alk, which is the best measure. This is not pH. You can have very low alkalinity and still not be acidic. It is essentially a measure of the buffering capability, which tells you how much acid has to be added to move the pH a fixed amount. But even so, if no acid is added, the pH doesn't move. And while acid rain affects everywhere, some areas have far more acidic rain than others, and it can be quite localized.
T_Alk < 10 is infertile. Most freestoners are in the teens and 20's, and richer freestoners can get up to numbers like 30, 40, even 50 (generally bigger valley streams). Limestone influenced streams are generally 100+, and "pure" limestoners will often be in the neighborhood of 200, for comparison.
But I will almost never blame fertility alone for a total lack of fish. Acid, yes. And fertility leads to resistance to that. But acid is still the cause. Other causes include summer water temperatures, streams drying up, and other forms of pollution. In rare occasions, the stream CAN hold fish but for some reason they got wiped out at some point, and never recovered due to a lack of a connection with a breeding population.
In most cases, when you have a situation where one stream has fish and a neighboring, seemingly identical stream does not, the cause is acid rain, and the reason for the difference is natural buffering capability based on the rock strata the respective streams flow through. Even a short distance through a more soluable rock will make a stream more resistant to the effects of acid rain. That's why limestone sanding works.
