Current PA Brook Trout Population as Percentage of Original?

[k-bob]

right forgot about that... less than of 100 % of PA had brookies in 1492

 

[FarmerDave]

Sorry for coming to this late.

troutbert wrote:
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'd say about the same, maybe a little bit less. But here are a few things to consider.

First lets establish that this is to be an apples to apples comparison. make a lit of best 5% and compare them to the exact same streams before Europeans.

If you and I assessed all the streams and we both picked out what we think are the 5% best brook trout streams today, our lists would likely be different. My 5% would indeed have similar habitat to what they did before Europeans complete with LWD.

Now here is the kicker. If we come up with a lost of the best 5% of today and compare that to the best 5% back then. The best 5% today would have WAY less because they would be completely different streams. The best brook trout streams before Europeans arrived now likely are dominated by brown trout.
There are so many things to consider.

But back to your original question. I'd put the biomass of brook trout today (in PA) at less than 10% of what it once was before Europeans.

Probably less than 5%

For those that think it might be higher, here is an interesting math exercise.

Pull up the list of ALL class A trout streams. Now, count the number that are class A for Brook trout and divide that by the total.

The number is likely quite small and that is only percentage of stream sections. Consider that the class A for brook trout are the smallest, it is not much of a stretch to come up with 10% and that is likely very conservative.



I hope I didn't repeat someone else's. If I did, I apologize. The thread is long and I only read part way.

 

[k-bob]

We all agree that current total brookie PA biomass must be much less than 1492 total PA brookie biomass. I'd probably say 20%. That's a higher number than anyone else gave. My thinking: hemlocks are poor for in-stream invertebrate productivity, so the old biomass level may be less than we imagine. But everyone else said half that much or less. ??

The more interesting question to me is whether any of the PA streams that currently have brookies had fewer brookies in 1492. My guess is a few. Pat said that a rare few may have improved.
TB care to weigh in on that? Buckeye Bullet?

 

[FarmerDave]

troutbert wrote:

troutbert wrote:

pcray1231 wrote:

I'm not so sure it's true that old growth results in more LWD than modern successional forests, though. There's certainly more woody debris in your typical 80-130 year old mixed forest than there is in the pockets of virgin, mostly Hemlock, forests I've been in.

Where were you seeing this? (The streams flowing through pockets of mostly hemlock old growth forest?)

BTW, this question is not just for pcray. I'd be interested in any stretch of stream people have seen flowing through old growth forest in PA. There are probably very few such stream stretches, but I'm interested to go see the ones that exist.

Most old growth that I know of is on hilltops in PA, so you usually don't see streams flowing through old growth in PA. But I do know of a couple. However, IMO Pat's reasoning is sound. Old growth forests are stable and dominated by trees that are hundreds of years old. When one falls, it creates an opening that quickly closes up because of the fast growth of conifers.

Trees in mixed secondary growth actually fall more frequently.

As far as naming streams, I won't get into that. But a lot of streams I used to fish for brook trout were so choked with LWD that it was virtually impossible to flyfish.

Troutbert, you do have a good point about LWD. It applies to the majority of streams, but not all.

 

[troutbert]

FarmerDave wrote:

Now here is the kicker. If we come up with a lost of the best 5% of today and compare that to the best 5% back then. The best 5% today would have WAY less because they would be completely different streams. The best brook trout streams before Europeans arrived now likely are dominated by brown trout.

That's a good point. They would be different streams.

Here's something to think about:

I. The population of brook trout in the Little Juniata River, back in the day.

II. The population of brook trout in all of Potter County today?

Which would be greater? And by how much?
Explain your work. ;-)

 

[FarmerDave]

k-bob wrote:
We all agree that current total brookie PA biomass must be much less than 1492 total PA brookie biomass. I'd probably say 20%. That's a higher number than anyone else gave. My thinking: hemlocks are poor for in-stream invertebrate productivity, so the old biomass level may be less than we imagine. But everyone else said half that much or less. ??

The more interesting question to me is whether any of the PA streams that currently have brookies had fewer brookies in 1492. My guess is a few. Pat said 5%.

TB care to weigh in on that? Buckeye Bullet?

What if we say the closest without going over, wins.;-)

And leave Dave Blaney out of this.

 

[FarmerDave]

troutbert wrote:

FarmerDave wrote:

Now here is the kicker. If we come up with a lost of the best 5% of today and compare that to the best 5% back then. The best 5% today would have WAY less because they would be completely different streams. The best brook trout streams before Europeans arrived now likely are dominated by brown trout.

That's a good point. They would be different streams.

Here's something to think about:

I. The population of brook trout in the Little Juniata River, back in the day.

II. The population of brook trout in all of Potter County today?

Which would be greater? And by how much?
Explain your work. ;-)

That is a tough one and I don't know Potter county or LJ very well. But if you picked Forest County, and Penns Creek, I'd say Penns Creek.

Forest County is still over 90% forested, and damn near every stream has brook trout, but not many.

 

[FarmerDave]

How about this one.

Total biomass of ALL trout in Clarion County today compared to same area in 1492?

I'm going to say less than 1% but increasing.

 

[k-bob]

let's look at it from a fishing perspective: the state of PA can never have its brookie biomass from 1492 again.

are there any individual streams in PA with greater brookie biomass right now than the same stream had in 1492?

 

[Chaz]

I'm going to say, it's 95% less biomass then it was pre 1492. Additionally it has to be very high, because of the EBTJV estimate of 85 % loss of streams.
The map in the status only shows the streams we know that had brook trout when records started being kept.

 

[k-bob]

I'd probably agree, only a handful of PA streams say 5% (steep, groundwater, no browns) have more brookies now than 1492. Main reason they could have more ST biomass now: more aquatic bugs in streams of hardwood forest, versus streams of old hemlock forest there before.

http://harvardforest.fas.harvard.edu/sites/harvardforest.fas.harvard.edu/files/publications/pdfs/Willacker_NEN_2009.pdf

 

[FarmerDave]

k-bob wrote:
let's look at it from a fishing perspective: the state of PA can never have its brookie biomass from 1492 again.

are there any individual streams in PA with greater brookie biomass right now than the same stream had in 1492?

Not likely... Or at least if any do exist, the numbers would be insignificant and differences would be negligible. Mother nature is way better at building trout streams than man is.

 

[pcray1231]

I. The population of brook trout in the Little Juniata River, back in the day.

II. The population of brook trout in all of Potter County today?

Which would be greater? And by how much?

Hmm. Good question.

I don't know the answer. But I'll show the back of my envelope for you, and feel free to tear apart the assumptions. They are nothing more than guesses, and I'd be happy to massage this into something more accurate.

Potter County has roughly 380 wild trout streams listed by the PFBC.
We'll say 325 of those are primarily brook trout.
And we'll say the average length is 3 miles, considering that some are much longer but many are little trickles that are shorter.

So we have 975 miles of brook trout water in Potter Cty.

Now, the average width is probably, what, 1/20th of the LJR? So all of Potter County has the trout holding surface area of approx 50 miles of the LJR.

Now, the LJR certainly has more fish per surface area. It's deeper. It's more fertile. Because it's bigger and more fish are in the riffles, a greater % of it is fish holding water than the little streams in Potter. We'll make that a factor of, what, 5? Meaning, per square foot of surface area, the LJR has 5 times as many fish as your AVERAGE Potter County brookie stream. Seems close to reasonable.

That would say that ALL of modern Potter County is approximately equivalent, in number of brook trout, to what 10 miles of the LJR is capable of holding.

 

[k-bob]

" Mother nature is way better at building trout streams than man is."

that is kind of the assumption.. mankinds influence is one way downward ratchet. and it usually is ...

 

[FarmerDave]

K-bob, I typed that last one before you provided some explanation. I'll admit that your explanation might have some merit.

However, IMO, the streams that now have more aquatic bugs and such as a result are likely now brown trout streams.

Most of the brookie streams are still on the acidic side which means less fertile.

I don't subscribe heavily to hemlocks mean less trout. IMO they do more good than harm. They thrive on acidic soil, they don't necessarily cause it. That is just opinion though. I haven't studied it.

 

[pcray1231]

Oh, they cause acidic soil. No question about that. Use pine needle mulch on your flowers and see what happens....

It's largely seen as an evolutionary trait. Acidify the soil to reduce much of the competition. But then other plants evolved to thrive in that soil. Blueberry, rhododendron, etc.

 

[k-bob]

issue is a little different. not that hemlocks cause acidic soil. issue is that trout eat aquatic invertebrates, while aquatic invertebrates eat leaf litter (look it up). the old hemlock leaf litter decays slowly and is poor food for aquatic bugs. replacement mixed hardwood leaf litter is much better. see the charts here for hemlock vs maple as aquatic bug food:

http://www3.nd.edu/~underc/east/publications/documents/Maloney_94AMN.pdf

so where logging switched the forest from hemlock to hardwood around some still-cold streams: now more aquatic bugs w/ hard wood leaf litter, and more trout biomass? even if man made the switch.

rare exception? yes. impossible? I don't think so...

 

[k-bob]

the study below examines aquatic invertebrates in DWGNRA headwater streams. it found 2.7 times greater aquatic invertebrate density under hardwood than hemlock canopies. this is attributed to the fact that hemlock needles are a poor food source for in stream invertebrates compared of the leaf litter of second hardwood forests.

Influence of eastern hemlock (Tsuga canadensis) forests on aquatic invertebrate assemblages in headwater streams

Craig D Snyder, John A Young, David P Lemarié, David R Smith

if a stream has the ground water to stay cold in thinner canopy, more benthic bugs w/ hardwood can lead to more brookie biomass after logging of hemlock. why not?

 

[k-bob]

or this study of stream bugs and the e hemlock:

"Stream Macroinvertebrate Communities in Paired Hemlock and Deciduous Watersheds"

abstract: "Abundance, taxa richness, diversity, and unique taxa were generally greater in the deciduous stream."

http://www.bioone.org/doi/pdf/10.1656/045.016.0108

changing the trees can influence the fish, folks...

 

[FarmerDave]

pcray1231 wrote:
Oh, they cause acidic soil. No question about that. Use pine needle mulch on your flowers and see what happens....

It's largely seen as an evolutionary trait. Acidify the soil to reduce much of the competition. But then other plants evolved to thrive in that soil. Blueberry, rhododendron, etc. [/quote]

Are you saying that the hemlocks produce the acid, or are acidic because of the soil?

Either way, I argue the good outweighs the bad. Best brook trout streams I know flow through mostly hemlock.

And if you think deciduous leaves are acidic, think again, and the deciduous create way more forest litter.

But again, k-bob does have a point.