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Re: Current PA Brook Trout Population as Percentage of Original?

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Quote:
Percent of watersheds where brook trout were once present that still hold brook trout.
-Green: 1% relatively intact (~90% occupied)
-Yellow: 9% present in reduced percentages (50-90% occupied)
-Red: 39% existing but greatly reduced (<50% occupied)
-Gray: 34% extirpated


The big question is "what does occupied mean"?

Take the red category. "existing but greatly reduced (<50% occupied)".

Does that mean that greater than 50% of the actual streams in the watershed that once held brook trout no longer do?

Stream miles?

Does it mean that the watershed has lost >50% of it's fish, in numbers?

In biomass?

Depending on what you're measuring, it means VERY, VERY different things.

FWIW, I flat out don't believe it means number of streams, because in many of those red areas, >50% of the streams still do hold brook trout. Just doesn't add up.

If by stream miles, maybe. It takes a lot of those little streams, at 1 or 2 miles a pop, to equal the mileage of the larger streams which were indeed lost.

If by number of fish, yeah, I buy it. It takes even more of those little streams, at 1 or 2 miles a pop and a width you can jump across and a couple of fish in each pool a few hundred feet apart, to match the population which was lost in the bigger water.

If by biomass, it's probably an overly optimistic assessment of the situation. I struggle to believe there's any green or yellow in PA!

Posted on: 3/6 15:06


Re: Current PA Brook Trout Population as Percentage of Original?

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Quote:

pcray1231 wrote:
Quote:
Percent of watersheds where brook trout were once present that still hold brook trout.
-Green: 1% relatively intact (~90% occupied)
-Yellow: 9% present in reduced percentages (50-90% occupied)
-Red: 39% existing but greatly reduced (<50% occupied)
-Gray: 34% extirpated


The big question is "what does occupied mean"?

Take the red category. "existing but greatly reduced (<50% occupied)".

Does that mean that greater than 50% of the actual streams in the watershed once held brook trout, and now don't?

Stream miles?

Does it mean that the watershed has lost >50% of it's fish, in numbers?

In biomass?

Depending on what you're measuring, it means VERY, VERY different things.


I think it's referring to stream miles, not population. But I'm not sure.

And the question of what the criteria is for "occupied" is a good one. What is the minimum quantity of brook trout used to put stream mileage in the "occupied" category? And were the same criteria used in different states?


Posted on: 3/6 15:11


Re: Current PA Brook Trout Population as Percentage of Original?

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The data are from the EBTJV pamphlet for PA and were generated by the PFBC. The pamphlet says the percentage shown is from subwatersheds. Unfortunately, what constitutes a subwatershed is not described. As I recall from the presentation, subwatersheds are defined by dividing the state into small parcels and then determining whether brook trout lived there at one time and the current status. The number of parcels (subwatersheds) with brook trout populations in the past can then be compared to the present situation. It's not perfect, but does give one a pretty fair idea of the status of brook trout in PA.

Posted on: 3/6 16:25


Re: Current PA Brook Trout Population as Percentage of Original?

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There are regions there, painted red, where virtually every single small stream holds brook trout. The % of ALL streams currently containing reproducing populations is probably somewhere north of 80%. So it is impossible that brookies were totally extirpated from >50% of streams that used to hold brookies in those regions.

That's my issue. But I tend to think by stream, not by stream miles.

So say you have a medium sized stream, with 30 little tribs, all of which contained brookies. Now the larger stream lost it's brookies cause it's too warm, and maybe 2 of the bigger tribs as well, as they were taken over by brown trout. But 28 still have em, though maybe in somewhat reduced numbers because of acid rain reducing the fertility of said stream. Very common situation.

If you treat it as 31 separate watersheds, now 28 of them still have brookies, and were lost in 3. Far more than 50% still hold fish. If you treat it as 1 watershed, well, it still is "occupied" by brookies in far more than 50% of its member streams. Either way, it shouldn't be red. Which is why in my mind, at face value, the map seems like B.S.

But that 1 bigger stream and it's 2 larger brookie free tribs may indeed constitute >50% of the traditional fish holding mileage, acreage, # of fish, biomass, etc., which would make the map not wrong, but merely lacking a clear enough explanation.


Posted on: 3/6 16:56

Edited by pcray1231 on 2014/3/6 17:17:35
Edited by pcray1231 on 2014/3/6 17:18:46


Re: Current PA Brook Trout Population as Percentage of Original?

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if you look at the excellent PowerPoints about unassessed streams also on the conservation forum, I guess the better ones aren't so different in brookies from way back...

Posted on: 3/6 19:54


Re: Current PA Brook Trout Population as Percentage of Original?

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Quote:

k-bob wrote:
if you look at the excellent PowerPoints about unassessed streams also on the conservation forum, I guess the better ones aren't so different in brookies from way back...


Why do you think that is the case? What info in the Powerpoint presentation is leading you to that conclusion?

I did read through the PowerPoint presentation.

Posted on: 3/6 21:33


Re: Current PA Brook Trout Population as Percentage of Original?

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for a tiny stream in a forest, pre euro there might have been a few plus factors for trout ( no acid rain so higher fertility) also minus factors (more mink, birds of prey, etc; more hemlocks w/ acidic needles, a strong minus for fertility).... may not have been so different for trout overall

I wonder just how acidic a stream would be in a heavy hemlock forest

some streams might even have more fish now

obviously just a crazy guess that tiny remote streams overall might not have been that different in the number or size of trout

Posted on: 3/7 4:51

Edited by k-bob on 2014/3/7 5:35:41
Edited by k-bob on 2014/3/7 5:37:20
Edited by k-bob on 2014/3/7 5:38:07
Edited by k-bob on 2014/3/7 5:39:05


Re: Current PA Brook Trout Population as Percentage of Original?

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see image below... pre-euro heavy hemlock forests along tiny streams might have produced acidic water (fewer aquatic bugs) and had limited brush for bugs on forest floor (fewer terrestrials). what's a brookie to do?

a tiny stream with swampy headwaters that runs through an intact hemlock forest might even be too acidic for brook trout to live in ... and a lot of hemlocks were cut down back in the day. some mountain streams still have OK water temps.

I love hemlock forests, but they may not have lead to better conditions for tiny stream brookies than the mixed forests that replaced them? the good old days for some tiny stream mountain PA brookies may be .. now?

(part of the reason for "# deer chart" earlier in thread: no guarantee of fewer animals in some envts now versus pre-Euro)

if that is right, the ebtjv map, at least drawn down to the level of tiny-stream brookie health, might look very different. does it need a "more brookies than 15th C" color ?:)

anyone who actually knows what they are talking about, please jump in here ... I was only around for the 19th C, not the 18th :)

Attach file:



jpg  hemlock1.jpg (45.32 KB)
2769_5319b5a5a15bc.jpg 500X378 px

Posted on: 3/7 7:03

Edited by k-bob on 2014/3/7 7:19:36
Edited by k-bob on 2014/3/7 7:20:21
Edited by k-bob on 2014/3/7 7:41:28
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Edited by k-bob on 2014/3/7 7:47:33
Edited by k-bob on 2014/3/7 7:48:37
Edited by k-bob on 2014/3/7 7:49:04
Edited by k-bob on 2014/3/7 7:55:17


Re: Current PA Brook Trout Population as Percentage of Original?

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I thought you meant there was something in the unassessed waters PowerPoint that indicated that the best of the brookie streams today are likely to have populations similar to what they were in the past.

It should be considered as an open question. Do the best brookie streams today have populations that are lower, higher, or about the same as in the past?

Suppose you took a slice of the best brookie streams today, let's say the top 5%. Would to total populations of those streams be lower or higher or about the same?

I think the populations of those streams would be lower, MUCH lower, than in the past.

I realize that doesn't sound intuitive. There is a common idea, which I've often heard and read, that the forests were cut over, the brookies suffered, but now the forests have regrown, so conditions have recovered to similar as before.

But I don't think that is the case. There are still many differences that impact the brookie populations in the best brookie streams.

But the most important factor is the physical habitat of the streams, particular the "holding water" for trout, i.e. pool habitat and overhead cover.

One of the reasons for this is that in forested floodplain streams, much of the pool formation comes from large woody debris, LWD. And LWD levels now are a small fraction of what they were historically.

The accumulated LWD was removed during the logging days, for splash damming. And though the forests have grown back, they are young to medium aged forests, so they produce much less large woody debris, both in numbers of downed trees and in the size of the fallen trees.

In places you can see where there is some good large woody debris, how it creates excellent pools and cover for the fish. A single big downed tree can transform a shallow featureless stretch into a pool that is waist deep, and also has good places to hide in under the tree. I've seen places where one fallen tree created TWO pools, one below the tree and another above.

In the pre-logging era, the forested floodplain streams would have been jumbled with downed trees and logjams. It would just be pool, riffle, pool the whole way up the creek. Such places exist in old growth forests in the west and Alaska.

Besides LWD, other remaining impacts include channels were straightened for splash damming and for building logging rr grades. And many of those remain straight today. Many channels were pinned, constrained, separated from the floodplains by logging rr grades. They cannot meander and form meander bend pools. LWD does not "stick" because the stream is a straight chute. Floodwaters are contained within the channel rather than going out across the flood, creating excessive scour.

There are also grade control issues caused by lack of LWD, and by channelization of streams further down, that extends up into the backcountry areas through nickpoint migration. That is why there are so many stretches running on flat bedrock. The streams have incised down to bedrock because of loss of grade control.

Another thing that is surprisingly common is stretches of stream that are still impacted today by "legacy sediment" on the floodplains left by old splash dams and sawmill dams. The sediment accumulated on the floodplains behind these dams, several feet thick. When the dams were removed or broke down, the streams cut down through that sediment. The physical habitat, particularly pools, is usually very poor in these stretches.

Then there are the gas line crossings, powerline cuts, ATVs riding through the streams.

And also harvest of trout. Even the backcountry streams get hit. Some more than others. But many of the streams in good condition (by todays standards) are known and people fish them and harvest fish.

Posted on: 3/7 8:46

Edited by troutbert on 2014/3/7 9:02:15
Edited by troutbert on 2014/3/7 9:12:06
Edited by troutbert on 2014/3/7 9:21:52
Edited by troutbert on 2014/3/7 9:26:38


Re: Current PA Brook Trout Population as Percentage of Original?

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TB, you bring up a very interesting factor .... I wonder how true it is for very small steep streams?

even if streams were altered, a stream with seven percent plus elevation change over half mile still has pools... And I am not sure that very steep streams ever meandered so much -- too much energy in a flood for that? steep streams probably resist human intervention.

as important as pools are, fertility and the terrestrials are still very important also ... not clear to me that hemlocks were better than mixed from a stream acidity and ground vegetation point of view..

who knows? but I still think there may be a some streams with more trout now than in the 15th century

tropical storms have put in LWD for example.. not just sandy and the 11 hurricane, but the 50s NEPA floods etc. LWD put back after logging in many cases, logging in many areas now 125 years ago?

TB, so to be clear, is it your view that if we had data for all the PA streams pre euro & present, incl tiny steep mountain ones, almost none would have better brookies now? not my guess.


Posted on: 3/7 8:54

Edited by k-bob on 2014/3/7 9:14:35
Edited by k-bob on 2014/3/7 9:18:09
Edited by k-bob on 2014/3/7 9:19:52
Edited by k-bob on 2014/3/7 9:21:49
Edited by k-bob on 2014/3/7 9:23:19
Edited by k-bob on 2014/3/7 9:25:55
Edited by k-bob on 2014/3/7 9:26:44


Re: Current PA Brook Trout Population as Percentage of Original?

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2011/6/29 9:38
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Okay, you guys have got my juices flowing to fish some remote backwoods stream. The kind that probably still have 15 inches of snow to walk through. Uggggggggggggggggggg!

I want the spring to be here!

Posted on: 3/7 8:56


Re: Current PA Brook Trout Population as Percentage of Original?

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it's gonna warm up George

Posted on: 3/7 9:24


Re: Current PA Brook Trout Population as Percentage of Original?

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I'm actually watching youtube videos in my office of native PA brook trout fishing and living vicariously through those guys LOL

Posted on: 3/7 9:37


Re: Current PA Brook Trout Population as Percentage of Original?

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In steep narrow gorge streams, the physical situation is different than in streams with well developed floodplains.

On the gorge streams, you have more influence of rocky habitat, i.e. bedrock features, such as ledge pools and waterfall pools. And in some places more influence from large boulders. Those rocky features would have been there before and are there now.

But, two things to consider:

1) The stream mileage of the very steep gorge sections of stream, with good rocky habitat, is a very small percentage of the brookie stream mileage in PA.

2) Even on steep ravine or gorge streams, the effect of large woody debris is very significant. It creates step pools, much in the same way that large boulders creates step pools. So while there may still some nice pools on those streams, from ledges and/or boulders, there are still far fewer pools because there is much less LWD than in the past.

And the LWD also acted as a grade control. On many of those streams, you will have some ledge pools and pockets, then long stretches where the stream is running of flat bedrock. Which we call "walk past water."

Many of those stretches in the past would not have been running on flat bedrock, and would not have been "walk past water." There would have been LWD jams that would have maintained a cobble substrate, and formed pools in that substrate.

Regarding the idea that the water quality would have been worse in the past, because of hemlock pollution. I don't think that is true. The forests were not 100% hemlock in the past. There were plenty of hardwoods as well. In many places there are lots of hemlocks today along the stream and the water quality is fine for supporting brookies.

The waters would have been far less acidic in the past, since there would have not been acid deposition from coal burning and other sources.

So, yes, I think that the top brookies streams today, let's say the top 5%, have lower populations than in the past. MUCH lower. Of all the reasons I've gone over, the main reason is because of pool habitat. The population of trout is very much related to pool habitat. And the amount of pool habitat on the freestone streams is far less than in the past because of the loss of LWD, and channel straightening and relocation, channel constraints (grades, rock walls), and loss of grade control, and therefore channel incision, extreme instability and scour during floods.

And I've only scratched the surface here. There is a lot more. But bottom line, the streams are physically very different, i.e. worse, than in the past. They are much more shallow, lacking in pools, so the trout populations that can be supported are much less. Things could be done to start remedying this. But that's another topic.

Posted on: 3/7 9:38


Re: Current PA Brook Trout Population as Percentage of Original?

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still not clear what you mean by top 5%? then? now? diff betwn then & now?

for clarity, is the idea that if we had data for all pa streams, incl tiny steep mountain ones, then and now, that in almost none would brookies be greater now?

my guess: with good water temps & pH, steep structure, and LWD from trpcl storms in the 100+ years since logging, I suspect some PA streams have better brookies now in mixed forest than hemlock...no way to really know of course

Posted on: 3/7 10:00

Edited by k-bob on 2014/3/7 10:38:57



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