using bedrock geology info to fish in acidrain areas

[k-bob]

"So, in fertile watersheds, why do the browns not totally displace the brookies in the upper ends? I don't know, but it's not about pH, IMHO." ... " It may be related to groundwater temps for spawning being more favorable for brookies than browns."

maybe feeding, but in a different way? there is slightly colder water in the headwaters, and I think the rosenbauer small stream book says browns don't grow as well as ST in colder water

 

[sarce]

I think browns may simply need/prefer a bit more space or slightly deeper water than the brookies. At least the adults anyway, since they tend to run larger than the adult brookies. Just a thought, I don't really know either.

Great info here btw, thanks.

 

[Chaz]

troutbert wrote:
I think that the brook trout and the brown trout would increase in roughly the same proportions.

And it's quite possible that the brook trout would improve at a higher proportion than the browns.

In the infertile watersheds, brook trout would re-inhabit the headwater stretches which presently hold no fish.

Below these headwater fishless stretches are commonly long stretches that hold brook trout but which are still very infertile. If pH of rainfall was returned to a normal 5.5, these stretches would still probably not support brown trout. The brook trout would improve here as a result of better food supply.

Further down, yes, there would be some increases in the range of brown trout in the upstream direction.

But I think the increases in brook trout would be as great or greater than increases in brown trout populations. In the infertile watersheds there would still be only brook trout for many miles down.

In the fertile watersheds, I'm not sure there would be much difference. Because the brown trout are not currently limited by pH in those watersheds. Often these streams have pH suitable for brown trout as far up as there is water. But the headwaters of these streams are still typically all brookies for a ways down. Then the brown trout appear, but they are still typically outnumbered by the brookies for a ways further downstream. Then you get to a zone where they run about 50/50, and the ratio continues to shift towards more browns / brookies as you continue down.

But this does not seem to be pH related. Because the pH is within the range for browns from right up where the streams originate the whole way down.

So, in fertile watersheds, why do the browns not totally displace the brookies in the upper ends? I don't know, but it's not about pH, IMHO.

It may be related to groundwater temps for spawning being more favorable for brookies than browns. Or it may be that brookies survive better in droughts in the small streams. Some PFBC survey reports during a severe drought stated that their data indicated that.

TB, Your last paragraph is probably spot on as to the reason why. I would add that if the upper reaches of those streams because of temps and droughts have different macros, then the macros may some how favor the brookies. I've never found anything on that aspect, but I never really looked either.

 

[Chaz]

sarce wrote:
I think browns may simply need/prefer a bit more space or slightly deeper water than the brookies. At least the adults anyway, since they tend to run larger than the adult brookies. Just a thought, I don't really know either.

Great info here btw, thanks.

All things being equal, if you were to take 2 streams that were the same PH, the same temperatures throughout the years, and had all else equal except species, browns in one stream brookies in the other, the brookie stream would have the same size structure as the brown stream.

Again, all great stuff.

 

[sarce]

Chaz, do you have any studies or other sources that came to that conclusion? I would be interested in reading them. I was under the impression that, all other things being equal, browns will grow faster and bully the brookies around, which is how they displace them. But I could also see brookies losing out simply because browns are more aggressive toward other fish.

 

[pcray1231]

There are a number of streams where its all browns way up to the headwaters. In those cases, yes, browns run small just like brookies in the same situations. And they act more like brookies too.

As for why they can't do that in all streams? I dunno, but suspect generalities doesn't cut it. Each stream is unique and may have a unique reason. I do suspect pH is a common reason. But temperature, structure, food base, availability of spawning beds, etc. are possibilities as well.

There's also simple opportunity. All else being equal, a habitat may be capable of supporting lots of browns. But all else is not equal. A few brown invaders may struggle to get a substantial foothold in the face of a healthy established brookie population. Introduce a temporary disaster to make both species re-establish from scratch, and all bets are off. This has happened in places.

 

[troutbert]

pcray1231 wrote:
There are a number of streams where its all browns way up to the headwaters.

What are some examples?

 

[pcray1231]

As for examples, I'm excluding true limestoners, or streams typically thought of as limestoners. But some of these likely may have a touch of limestone influence as some of the alkalinity values are in the upper teens and 20's. These are listed class A browns with headwaters as upper limit. It's not all of them listed like that, just what I picked out in a minute or two looking at the list. I've fished a couple, others I haven't.

Berks Cnty: Hay Creek, Beaver Run
Columbia: Mugser Run, Roaring Creek, Tenmile Creek
Centre: Rupp Hollow
Clinton: Shingle Branch, Spring Run
Lycoming: Mill Run
McKean: Lewis Run
Potter: Dingman Run, Bear Creek
York: Rambo Run

 

[RLeeP]

I'd have to cogitate on some of the streams on that list in order to form an opinion as to why they present exceptions to the ST dominated headwaters/mixed middle sections/BT dominant lower sections model. In some cases, geology and its effects on Ph may be primary. In others, probably not. My guess is that most are a mix of factors and that in some cases, decent alkalinity may be contributory but a different factor is actually determinative. For example, the situation on Lewis Run is probably more indicative of the fact that it is directly accessible to the strong wild BT pop. in the EB Tunungwant Creek than anything to do with Ph. I don't know what Lewis Run's alkalinity numbers are, but my guess would be that even if they were no better than the average stream in its size class in that area, it would still be dominated all the way to the headwaters by BT.

Something similar may be the case with Dingmans, the difference being the replenishing factor could be large browns from the Allegheny who spawn in Dingmans. There probably aren't a lot of these fish, but it wouldn't take that many to do the trick.

There are probably a lot of streams in that same situation and probably quite a few as well where the chemical characteristics are perfectly fine for browns but ST remain dominant because they lack direct connection to a stream with a potent enough BT population to overwhelm the dominance of the brookies.

 

[troutbert]

Shingle Branch has a lot of brook trout, as well as browns.

In Mill Run also I've caught both browns and brookies.

Dingmans also has both browns and brookies.

So, I don't know why these would be considered exceptions. They fit the general pattern for fertile freestoners, i.e. the mix of brookies and browns strongly favoring the browns in the lower ends, then shifting more and more towards brookies as you go upstream. And up where the stream gets quite small, the population is dominated by brook trout.

This happens even where the streams are fertile the whole way up. For example Kettle Creek.

And the headwater branches of the Genesee River, which are flowing out of fertile glacial till. Further down it's mostly browns. But up where those streams get quite small, it's dominated by brookies. It's not a pH thing, it's some other factor(s).

Another example is where you have a fertile freestoner with a mixed population, but more browns than brook trout. Where a small, secondary channel splits off the main channel, that channel will have a greater percentage of brook trout than the main, unsplit channel.

That is definitely not a pH thing. Because it's the same water flowing through both sections. The brookies seem to have an edge over the browns in the smaller, shallower stream sections.

 

[duckfoot]

Now that I think of it, the basic survivability instincts also are something to consider.

As tides go in or as water goes up, fish and crabs move with water to find food. As soon as that water goes down, fish disappear to deeper depths to prevent getting caught high and dry.

Browns = larger, deeper water fish...more scared of getting caught in shallow water?

Brooks = smaller, more agile fish...more thrifty and patient to extreme changes in the water column?

Just a passing thought.

 

[RLeeP]

Well, all we really have is the Commission's determination (based on the most recent couple of surveys, I guess..) that the streams under discussion from Pat's list are Class A for brown trout, which last I knew (admittedly a while ago..) meant that they had determined that 75% or more of the biomass from the marking runs (or whatever they call them...) was comprised of browns. I don't know where they do the sampling on any of them and I wouldn't be the least bit surprised if the percentage of brook trout rises as you go upstream. Still, based on the rules of the Commission's Class A system, these are brown trout streams all the way to the headwaters, not mixed Class A's.

I'd agree that Ph is probably not the determinative factor, at least not usually. As I said, my vote for primary factor, at least in some of them, would be for proximity to a stream with a strong enough wild BT pop to keep the ST population overwhelmed.

I don't know if this solves or clarifies anything and I don't even know if any of the three of us actually disagree about any of it... This just happens to be what I think...

 

[k-bob]

I don't know about this issue, but I like the idea that there are at least some brookies in many streams

 

[pcray1231]

As RLee states, I do not know specifics on all of those streams, including the ones you pointed out. Merely that the commission lists them as class A browns, NOT MIXED, to the headwaters. That's not to say that there are no brookies. It's also not to say the sampling is complete nor up to date. Just that according to the list, 75% or more of the biomass is brown trout the whole way to the top.

A few of them are indeed dominated by browns to the top, from personal experience.

In addition to pH, temps, structure, etc., RLeeP does bring up another good point regarding access to a truly BT dominated stream. Certainly, I've caught browns with a lack of brookies in some really tiny trickles, unnamed tributary size, that are near larger brown trout streams.

That is definitely not a pH thing. Because it's the same water flowing through both sections.

I'm not asserting that it IS a pH thing, and I do agree on the importance of other factors. But it COULD be a pH thing. It's the same water, yes. However, even in freestoners, there's a difference between the pH and buffering capability of spring water vs. pure runoff.

At the very top end of streams, during a rain/snow melt event, the % of flow from runoff (rather than springs) is much higher, hence your low pH spikes may be more severe. As you get downstream, a higher % is from springs. Further, keeping in mind that the source of a stream is generally from a single geological formation, which may or may not have any real buffering capability. As a stream falls, it may pass through other geological formations. Picking up springs with better buffering as it goes, and also some portion of the stream is usually flowing in the gravel under the streambed, which can offer some buffering.

 

[troutbert]

From both a practical fishing and a conservation perspective it's good to know that freestone streams that are listed as Class A brown trout, headwaters to mouth, typically also have a lot of brook trout.

This discussion raises an interesting question: Are there any freestone streams in PA that have wild brown trout, but that have zero native brook trout, even clear up to their headwaters tributaries?

 

[sarce]

Troutbert, I believe there are several such streams in the "River Hills" of the lower susquehanna valley. Mostly direct tribs to the river. I don't have a ton of experience fishing that area myself, but have heard a few streams there are browns only, which matches my few trips to those streams. Another example I can think of is Indian Run in chester county, I used to catch the odd brookie there but have not seen one in a few years. I think the browns took over. The kicker is that the headwaters are too slow moving and silty for trout, so it may not fit the description of the streams you're thinking of.

 

[RLeeP]

I'd be willing to say that the sort of streams you're talking about (with only wild BT all the way to the headwaters) probably aren't all that uncommon in portions of Pennsylvania. My guess would be that you'd find the majority of them in areas where development/agriculture has simply made it too difficult for brook trout to hang on. I'll bet there are quite a few in the SE, SW and I'm pretty sure I can think of a half-dozen or more just in Erie and Crawford Counties in the NW. Then, of course, on the other hand, I'd think such streams would be far less common in the more mountainous, less developed counties of the NC.

This is a fun discussion...

 

[troutbert]

Isn't Indian Run a limer?

It is very common for limestone streams to support wild brown trout, but no brook trout. That is the case in the majority of limestone streams in PA.

But not common in freestone streams. There may be some, but they are pretty rare I think.

 

[Chaz]

When the conditions are right in brookie only streams, brookies will grow to 14, 15 inches and can be abundant.

 

[sarce]

Indian run is an infertile freestoner. Very few browns over 13".