Current PA Brook Trout Population as Percentage of Original?

[pcray1231]

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

They produce the acid.

I don't know whether the good outweighs the bad on large scale or not. I do agree that there is both good and bad. Keep in mind, though, that the streams acidity is a function of the trees in the entire watershed, not just right along the stream. Hence, it is possible (though I'm not claiming it to be so), that the best situation is to have a mostly hardwood drainage area with Hemlocks along the stream itself.

Now the good and bad of Hemlock's (and pines in general) as it pertains to brookies:

Good:

1. Shade. Year round shade. Temperatures are more constant under coniferous canopies. Cooler in summer and warmer in winter.
2. Thick soils with excellent water capacity. Reduces runoff, and thus siltation. Creates more steady flows year round.

Bad:

1. Creates acidic soil, which creates acidic water.
2. Acidic water reduces aquatic bugs.
3. Acidic soil and shade reduce streamside vegetation --> reduces terrestrial bugs.
4. Soils and litter are low in nutrients --> reduces terrestrial bugs.

Unknowns (to me):

1. I'm not entirely sure that the effects of "acidic water" are as simple as measuring pH. The type of acid matters. Sulfuric acid may have very different effects than say, tannic acid, even at the same pH. Afterall, brook trout evolved in heavily pined forests. True, they are thus more resistant to acid than other trouts. But they may actually thrive in the type of water chemistry that results from pines.
2. LWD, as we've discussed. Logic tells me that fully mature pine forests should have less, but I'm not sure of myself.
3. Habitat/structure is a lot more than LWD. The soft, spongy, acidic soils of hemlock forests I've been in create narrow, deep, vertically sided streams, often with undercuts. And that may be good. Also, the banks tend to be heavily mossed, as moss loves acid. That may offer a home for lots of bugs, countering k-bob's claims.

How it all balances out, I dunno. I still tend to think Hemlock bottoms and hardwood hills might be the best of all worlds. Reduces the acidity somewhat but you still get the streamside benefits.

 

[Chaz]

pcray1231 wrote:

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.

And back in 1492 that 50 miles of the LJR would have been loaded with brook trout and probably headwaters to mouth.

 

[Chaz]

Don't forget that acid loving plants like mountain laurel and rhododendrons grow along those streams and all acid loving plants take up acid from the soil and water. Brookies did evolve in that type of environment, and there are many places like the Poconos and the ANF that are have acidic soils even today and plenty of tannic streams, there's a big difference between acid rain, amd, and tannic streams.
Much of the tannic acid comes from leaf litter, not just conifers and conifers take much longer to decay.
To answer the question of whether any broke streams have more brookies in them now as opposed to 1492, I doubt it, but since we don't have a baseline we will never know.

 

[Chaz]

So PA FBC estimates the number of wild trout to be approx. 5 million, I'd guess that half of that number is brookies, but that's just a guess. So 2.5 million. If the average weight of those fish is 8 oz. each, that equals 1.25 million lbs. of brookies. Divide that by 2000 (number of streams with ST) and it is 625 lbs per stream. It sounds like a big number, but it would be more accurate to divide it by mileage, 5000, and you get 250 lbs per mile and we know of no stream in PA that has that density of brook trout. More realistically a broke would weight 4 oz. on ave. so that would be 125 lbs. per mile. I know of only 2 streams out of all the brookie streams that the estimates are that high, and one hasn't been surveyed since Operation Future. And the 2 streams I know that are that high are very fertile freestone streams. Keep in mind this is all hypothetical. The point is we don't know what we'd have had in 1492, but we have to protect what we have and work to make them better.

 

[k-bob]

pat: some studies mention slightly more acidic water of streams in hemlock forests. hemlock needles are acidic.

bigger issue for trout is that aquatic invertebrates eat leaf litter. hemlock leaf litter is poor aquatic invertebrate food. it decays slowly and results in lower density of invertebrates compared to the hardwood leaf litter of second growth forests.

that's why the dwgnra study found more dense macros under hardwood than hemlock forests. it's the leaf litter, that is what aquatic bugs eat.

and different leaf litter is why headwaters streams now under hardwood, versus the pre logging hemlock, could have more aquatic insects today. with more aquatic inetrberates, the streams could have more trout than in the pre logging days ... would only apply to streams with enough ground water to keep cold temps under thinner canopy, but a lot of PA streams do that

 

[Chaz]

but when there is less Macro-invertibrates the fish eat more terrestrials and more fish. If they eat more fish they may end up with more biomass. We see this in some of our AMD streams I would not be surprised if we looked for it we'd find it in some infertile streams that have moderate populations in remote areas.

 

[k-bob]

"Aquatic invertebrates are important in many ways
•They are vital links in the aquatic food chain, conveying nutrients from plants and algae to larger organisms such as fish, frogs, salamanders, reptiles, birds and mammals."

http://mdc.mo.gov/discover-nature/common-plants-and-animals/aquatic-invertebrates

Aquatic invertebrates eat leaf litter. Logging that changed the trees from hemlock to hardwood could be a plus for aquatic invertebrates. Hardwood is better leaf litter for invertebrate consumption than hemlock (studies linked above).

=> changing the trees can change the leaf litter. changing the leaf litter can change the in-stream invertebrates. changing the in-stream invertebrates can, in streams with enough ground water input to have ST, change the trout. it's all connected.

universal? no. common? I doubt it, because of the water temp issue. in some cases? as described above, I don't see why not.

 

[pcray1231]

I don't doubt that pine needles offer less food for bugs. The plants in acidic soils, like rhodo, also are not exactly good bug food. But like I said, what it does give you is more streamside moss, and thats a fact. Lift a patch of moss on soil, not rock, and the ground underneath is literally crawling.

I'm not gonna take a position either way cause I'm not sure. What I can say is that deciduous forests helped some species of animals, and hurt others, but the overall effect on wildlife biomass and diversity is better, not worse. Hunters know this based on spending a day in a mixed hardwood forest, and then a pine one, and where you see more critters. That said, other manmade factors are at play as well if you are looking at the current big picture, , and most of them are bad.

Overall I have little doubt that man has had a negative effect on most brookie streams, and I'm certain it's had a devastating effect on overall brookie populations. But I also suspect the effect on a few streams has been positive. It's just the law of averages. There still exist over 3000 bookies streams on this state. I find it hard to believe there's not a dozen or two that have improved. It could be as simple as covering an exposed pyrite outcrop somewhere.

 

[k-bob]

chaz: "but when there is less Macro-invertibrates the fish eat more terrestrials and more fish. If they eat more fish they may end up with more biomass. We see this in some of our AMD streams I would not be surprised if we looked for it we'd find it in some infertile streams that have moderate populations in remote areas."

so there will be higher trout biomass w less invertebrates in water? not sure about that

 

[k-bob]

pat: "What I can say is that deciduous forests helped some species of animals, and hurt others, but the overall effect on wildlife biomass and diversity is better, not worse."

the studies I linked above say deciduous is better than hemlock for density of in-stream invertebrates. including in headwaters dwgnra streams.

 

[k-bob]

pc: "Overall I have little doubt that man has had a negative effect on most brookie streams, and I'm certain it's had a devastating effect on overall brookie populations. But I also suspect the effect on a few streams has been positive. It's just the law of averages. There still exist over 3000 bookies streams on this state. I find it hard to believe there's not a dozen or two that have improved. It could be as simple as covering an exposed pyrite outcrop somewhere."

I agree and would guess PA has more than 3000 brookie streams. If 2/3 of 4500 stream nat repro list has brookies that's 3000. These unassessed stream projects are finding more. Maybe 5000 in the state incl tiny trickles.

 

[pcray1231]

We tend to have this idea that without man, all wildlife populations would flourish. Even more pervasive is the concept of "balance". But thats not the way nature works. Nature is simply "whatever happens, happens". There were wild swings in any given population well before man. Species went extinct. Many were hanging by their teeth. Change is natural, and they affect different areas differently. And with every change there are winners and losers, and sometimes the very same species is a winner in one place and a loser a mere valley away.

What man did was accelerate change. This helped some species and hurt others.

When you say 1492 brook trout populations, they weren't the same as 1100, or 500, or 1000 b.c. Streams get better, streams get worse. A sinkhole forms because someone created a pond to put some bass in. An underground stream re-routes, maybe through limestone, maybe into an iron pyrite vein. That's nature. Man has caused more harm than good. But to think not a single stream got better, out of thousands, is foolish.

There are a couple of streams that are class A mainly because of nutrient input from sewage effluent.

Nature isn't governed by rules, with balances and stable populations. It's ruled by chaos theory. Where small changes can have large, and often unpredictable results.

 

[troutbert]

The hemlock/hardwood hypothesis is that stream chemstries should be less acidic than in the past because of a shift in vegetation.

But for that to be true the hypothesized hemlock/hardwood effect would have to be stronger than that of the effects of acid precipitation.

Does anyone believe that is the case?

It is well known that many miles of streams have lost their brookies entirely to acid rain. And many others have had their brookies greatly reduced. Because of acid precipitation.

How does the hemlock/hardwood hypothesis deal with that info?

 

[pcray1231]

The hemlock/hardwood hypothesis is that stream chemstries should be less acidic than in the past because of a shift in vegetation.

But for that to be true the hypothesized hemlock/hardwood effect would have to be stronger than that of the effects of acid precipitation.

Does anyone believe that is the case?

As far as straight pH, I don't think it's a contest. YES! Fresh pine needles have a pH of about 3.5. I've never heard of acid rain that low.

The pH does rise as bacteria composts them. I'm not claiming the soil is that low. Bacteria generally are basic. Hardwoods, such as oak, can be acidic too. But again, pine promotes less bacteria than hardwoods.

But I don't believe it's a straight question of pH, but type of acid matters. Acid rain is sulfuric acid. May not be the same as other types.

 

[k-bob]

TB: "The hemlock/hardwood hypothesis is that stream chemstries should be less acidic than in the past because of a shift in vegetation.

But for that to be true the hypothesized hemlock/hardwood effect would have to be stronger than that of the effects of acid precipitation."

Steam chemistries, like water temps, just have to be appropriate for trout. Trout only care about the outcome, not the process or some "natural" or historical level, or the "balance" with acid rain. if trout insisted on living in pristine environments unchanged by man, we might not have many wild trout 🙂

big picture:

1) Many PA streams lost first growth canopies to logging and now have mixed canopies. Read about logging: where hemlocks were taken, mixed forests of maple, cherry, etc now live. The insect pest now damaging hemlocks could also cause hemlock loss, with hardwood replacement. Much written lately because of the adelgid.

2) A stream that shifts from hemlock- to hardwood- drained forest would see changes in multiple variables. Yes, a small reduction in water acidity based on things I have read, in one case of paired study of hemlock and hardwood draining streams, the one under hardwood had a pH .25 higher. The pH difference was attributed to fewer acidic hemlock needles. Hemlocks were harvested because of tannic acid, right they produce acid. However, the pH level only has to be appropriate for trout, they don't calculate some balance w/ acid rain or anything else.

3) Along with a change in acidity, a switch from denser hemlock to thinner hardwood would allow light more light in and tend to raise water temps. The higher water temps in many cases were too much for brookies. That's the biggest issue in brookie decline with forest change and removal right there: higher water temps. However, we have all seen that some PA streams, usually small ones, have enough ground water to still provide cool enough water for brookies under thinner hardwood tree canopies. People see this in studies of streams under hemlocks that are being reduced by adelgids: With enough ground water input, streams can still be cold enough for brookies under suffering hemlocks.

4) My real point is that the well documented switch from hemlock to hardwood with logging altered a food chain involving trout. Hardwood leaf litter is more productive for in-stream invertebrates than hemlock leaf litter. Invertebrates eat leaf litter, and trout eat invertebrates.

why do I think think hardwood draining streams will have more inverbrates than eastern hemlock draining streams?

"The conversion of forests from hemlock to deciduous species is predicted to impact the hydrology, chemistry, and biology of associated headwater streams. In this study, we examined the macroinvertebrate communities of two adjacent headwater streams with differing hemlock influence in central Massachusetts. Abundance, taxa richness, diversity, and unique taxa were generally greater in the deciduous stream."

"Stream Macroinvertebrate Communities in Paired Hemlock and Deciduous Watersheds"

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

Similar effects were seen - 2.7 times higher aquatic invertebrate densities under hardwood than hemlock - right here in the DWGNRA in the thorough Snyder study I have cited here. (No free online version of that one, but a university library would have it.)

A shift from hemlock to hardwood happened over many PA streams. It logically lead to pH, water temp, and invertebrate density influences. The bottom line is that trout don't care about the historical or natural water temp, pH, or invertebrate level of an environment. Hemlock logging no doubt killed many more brook trout than it helped through higher invertebrate levels under replacement hardwood canopies.

5) So yes stream pH and water temps would both probably rise a bit when hemlock canopies are lost through logging or adelgid infestation. The water temp issue can be a great threat for brookies, but as in limestoners, where there is enough ground water, trout still live. Small headwater streams are often spring fed.

But no, trout don't worry about balancing an acid rain effect, or the historical or natural temp or acidity regime of a stream. They just live - if they can - in the water and food envt they find themselves in. We wouldn't have many wild brook trout in PA if they only lived in unchanged "natural" environments!

And there is good reason to believe that where the water temp is still char-friendly after logging (or adelgids) cause hemlock canopies to change to hardwood, there will be higher in-stream invertebrate levels.

food chain!=> trees drop leaf litter of varying productivity for aqauatic invertebrates, which eat leaf litter; hemlock needles are slow decaying and a poorer food source (sorry eeull gibbons 🙂) than hardwood leaf litter; trout eat aquatic invertebrates.

so imho a small minority of pa brook trout streams may have higher biomass now than in 1492. I am not defending logging, or the adelgid, just trying to be thorough about potential effects.

 

[pcray1231]

You're right on the water temps. It's not just amount of light reaching the water. It's also flows.

When a forest is dominated more by hemlock and pine in general, the soil can take and hold a heck of a lot more water. It's like a sponge. While it's well documented, you can feel it yourself when you walk through a pine forest and feel that soft ground beneath your feet. It's deeper, too, because acidic, nutrient poor pine needles don't compost as fast and easily as deciduous leaves do.

The result is that there's far less runoff. Stream levels don't rise as far in the spring, and they stay up in the summer, with a much higher % of the summer flow being groundwater.

And that's really why they're more acidic too. Oak leaves, for instance, are actually more acidic than pine needles. But they're also loaded with more nutrients, and compost easily. Once fully composted, everything trends towards neutral pH, including pine. But if you stop or slow the compost cycle, the acid stays. That's the case with soils dominated by pine. It's the case with hardwoods too if it's say, waterlogged, which is why swampy areas give you tannic streams.

Those tea colored waters would have been more the norm than the exception in the "old days".

And another "on the other hand", the original forests also had more beech. I think beech leaves are pretty basic in pH, and do compost well.

So how does perhaps improving pH, but allowing more flow and temperature variation affect streams? Well, you lose the big streams for sure due to temperature alone. Pine, Loyalsock, Oil, etc. And on overall brookie populations that's a quite devastating hit, those streams held the lion's share. The limestoners held on because they are still dominated by groundwater, though brown trout took them over, another devastating hit. But the small freestoners still stay plenty cool, in fact, a little warming combined with sunlight may HELP them by promoting bug life. Their summertime flows still drop more than they would have, exposing fish to predators and perhaps limiting fish movement. But that's combined with a slight pH rise, which is good. Which may be negated by acid rain, and I think sulfuric acid is more harmful than tannic acid at the same pH. But then you have changes in the stream structure itself, which can be highly variable and case specific. And LWD, which we've debated.

There's just a lot of factors at play, some good, some bad, and we're questioning how they trade off. My gut says the sum is a negative in far more cases than not, but also that the number where it's been positive is not zero.

 

[Chaz]

k-bob wrote:
chaz: "but when there is less Macro-invertibrates the fish eat more terrestrials and more fish. If they eat more fish they may end up with more biomass. We see this in some of our AMD streams I would not be surprised if we looked for it we'd find it in some infertile streams that have moderate populations in remote areas."

so there will be higher trout biomass w less invertebrates in water? not sure about that

Well not necessarily, you may have lower trout biomass, but bigger trout, often you find bigger trout where the population isn't high, in both brook trout and brown trout streams.
The ideal situation is when there's a balance of all habitat types in a drainage and plenty of cold water in the summer, then you have a good population of fish, some with impressive size, others just plenty of fish. Slate Run is a pretty good example, except that right now the fish populations seem like they are suppressed by floods. Kettle creek would also be a good example.
The thing about the streams in NC PA is that they have diverse habitats, great populations of trout and bugs. They all have fairly wide swings in temps that promotes diversity of bugs, but they don't get so warm as to kill fish. If those streams had 100%brookies, they'd probably have better pops now then pre 1492, given all of those factors.

 

[k-bob]

Chaz: "Well not necessarily, you may have lower trout biomass, but bigger trout.."

even if that is correct, from a conservation or preservation point of view, I think biomass is more important than the total number of bigger trout (a fishing issue?)

 

[Chaz]

pcray1231 wrote:

The hemlock/hardwood hypothesis is that stream chemstries should be less acidic than in the past because of a shift in vegetation.

But for that to be true the hypothesized hemlock/hardwood effect would have to be stronger than that of the effects of acid precipitation.

Does anyone believe that is the case?

As far as straight pH, I don't think it's a contest. YES! Fresh pine needles have a pH of about 3.5. I've never heard of acid rain that low.

The pH does rise as bacteria composts them. I'm not claiming the soil is that low. Bacteria generally are basic. Hardwoods, such as oak, can be acidic too. But again, pine promotes less bacteria than hardwoods.

But I don't believe it's a straight question of pH, but type of acid matters. Acid rain is sulfuric acid. May not be the same as other types.

At it's worst acid rain in PA was approaching the 3.5 ph. That pretty much kills everything, and it ruins the buffering capacity for a very long time. Streams that have been acid rain victims may be recovering, but all it takes is one event for them to get whacked again.

 

[pcray1231]

Acid rain doesn't really come in "events". At least not the pH of the rain itself, it's reasonably steady. The distribution of it to the stream is more variable.

Generally meaning, a high runoff, low groundwater penetration event puts more acid into the stream than a low runoff, high groundwater penetration event. Groundwater gets buffered (to various degrees depending on geology). So, a heavy rain on top of existing snow with frozen ground underneath is a high runoff event. An all day drizzle in the summer is a low runoff, high penetration event.