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> > Freestone vs. Limestone

Shawnny3June 10th, 2007, 5:29 pm
Pleasant Gap, PA

Posts: 1197
I've been in PA a few years now, and the distinction people make between freestone and limestone streams still eludes me. Can someone please tell me what the fundamental differences are between these designations?

Jewelry-Quality Artistic Salmon Flies, by Shawn Davis
CaseyPJune 10th, 2007, 7:00 pm
Arlington, VA/ Mercersburg, PA

Posts: 653
limestone stream: fed by springs flowing from limestone formations, therefore cooler in the summer and warmer in the winter. the slight alkalinity of the water is great for bugs and other food items. trout heaven.

freestone streams: everything else.

or at least that's what the guides at my first fly fishing school told us. they believed in the KISS principle of teaching.
"You can observe a lot by watching." Yogi Berra
GONZOJune 10th, 2007, 7:30 pm
Site Editor
"Bear Swamp," PA

Posts: 1681

In angling terms (especially here in PA), the distinction is often a loose one. Some PA streams are easy to classify as one or the other, and some have both characters within their watershed or within the course of the stream. Here in PA, limestone underlies much of what is known as the Great Valley, a long valley that curves southward alongside the Kittatinny Ridge. (The Cumberland Valley is in the southern part of the Great Valley in PA.) Belts of limestone or marble also exist in a number of other locations around the state.

Typically, PA freestones originate on mountainsides and are feed by seeps and hardrock springs. They tend to be more acidic and the hardrock base offers little buffering capacity, making them much more vulnerable to acid rain. They often have waterfalls and extensive pocketwater in areas with a steep drop, or a classic pool-and-riffle configuration. Because of low alkalinity, they are less fertile than the limestoners, but can have a greater variety of aquatic inverts (when healthy).

PA limestone streams might be loosely grouped into three categories: limestone spring creeks, freestone streams that are significantly influenced by limestone tributaries, and freestone streams that flow over a limestone base for part of their length. Of these, limestone spring creeks are the exemplars, and some of these emerge full-blown from high-volume springs that issue from limestone caverns. These caverns or sinkholes can also appear in the course of the stream, causing some to go underground at points along their course.

Classic limestone spring creeks, like the Letort, derive most of their volume from the headwater springs, often have a flat meadow character, host abundant weed growth, and have a more consistent temperature than freestones. Other true limestone spring creeks may have similar origins, but develop an atypical character due to terrain or the influence of non-limestone tribs. Penn's Creek has classic limestone origins, but picks up freestone and limestone tribs along its course and flows through varied terrain, giving it a diverse appearance and very diverse population of inverts. Big Fishing Creek is similarly diverse in terrain and critters. Spring Creek is more classic and has a less diverse assortment of water types and critters. (Some of the lack of critter diversity is also due to pollution, but even in perfect health, it still would not display the diversity of Penn's and Fishing.)

Some of the other streams we call "limestoners" here in PA come by the name through less direct means. These streams are basically freestone in origin, but are changed by the influence of significant limestone feeders or by flowing for some distance over exposed limestone belts. Such streams fit into the limestone category by degrees, and depending upon where you are on the stream, they may or may not display a limestone character.
KonchuJune 10th, 2007, 7:46 pm
Site Editor

Posts: 505
What are some of the bugs that you think would be in a "limestone" stream that wouldn't necessarily be found in a "freestone" stream? Just an aside for further discussion...
GONZOJune 10th, 2007, 8:17 pm
Site Editor
"Bear Swamp," PA

Posts: 1681

Because limestone streams with diverse habitat (like Penn's Creek) also display diverse invert populations, the differences may have more to do with habitat diversity than strictly limestone versus freestone. The classic flat meadow limestone streams around here have dense populations of mayflies like baetids and tricos, and much smaller populations of mayflies like the fastwater Heptageniidae or many of the stonefly species, but this is not true of some of the larger limestoners with more varied water types. Weed-loving species or species that favor higher alkalinity, like many of the scud species, are also in much greater abundance.
TroutnutJune 10th, 2007, 9:11 pm
Bellevue, WA

Posts: 2734
After fishing Penn's Creek, I'm not sure there is a difference. At least, there's an obvious difference in what the terms mean, but I don't think they're mutually exclusive. Penn's is a clear example of a stream which is both freestone and limestone.

The classic freestone streams are typified by the Catskill rivers, full of steep riffles, boulders everywhere, and prone to wild fluctuations in water level. But I would say anything with a lot of riffles and a rocky bottom could be characterized as freestone.

The classic limestone creek would be Spring Creek down by you, with that limestone color and fertility and a slow, weedy, meandering character. But Penn's and Fishing are also obviously limestone creeks, even though they also seem to have a freestone character.

The classic spring creek would, again, be Spring Creek by you (at least the part that I saw), or the White in northwest Wisconsin. Slow, weedy, meandering, and spring-fed, but not necessarily because of limestone. In northern Wisconsin the spring-fed streams come from regions with especially sandy soil, not limestone.

Some creeks still defy classification by this over-simplified system. The Namekagon is an example. It's spring-fed but the springs barely keep the temperature suitable for trout in the summer, because their volume isn't all that great. It never floods because the sandy soil offers so much stability, much more than in your mountainous limestone region, so the water level is much more stable than those spring creeks. It's got a medium-high gradient in most places so there are lots of riffles and it has the feel of a freestoner. Can it be a freestone spring creek?

Anyway, I think all we can use these designations for (spring creek, limestone creek, freestone creek) is to communicate a resemblance to the "classic" streams of each type. The varied spectrum of geology and hydrology of our trout streams doesn't allow for such simple categories to be any more concrete.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Shawnny3June 11th, 2007, 3:41 pm
Pleasant Gap, PA

Posts: 1197
Thank you, guys. I had a sneaking suspicion that I was asking a really stupid question (how does anyone in PA not know the difference?!), but from your responses I guess it wasn't that stupid a question after all.

It's been very enlightening.

Jewelry-Quality Artistic Salmon Flies, by Shawn Davis
IEatimagoJune 15th, 2007, 10:08 am
Spring Mills, PA

Posts: 97
i know one thing, i have never seen the amount of insects that i have seen since moving to penns creek area, and had never seen a limestone stream, and i am in awe.
i had never had a mayfly land on my porch before, and yesterday was at walmart and a sulfur landed in my car. i love central PA!
TroutnutJune 15th, 2007, 1:22 pm
Bellevue, WA

Posts: 2734
i know one thing, i have never seen the amount of insects that i have seen since moving to penns creek area, and had never seen a limestone stream, and i am in awe.
i had never had a mayfly land on my porch before, and yesterday was at walmart and a sulfur landed in my car. i love central PA!

Here in Ithaca that happens occasionally too. We bought a Venus flytrap the other day and have been feeding it mayflies and caddisflies from our porch light. We live right next to a small warmwater stream, but I've found mayflies around town in places several hundred yards from the nearest water. So finding aquatic bugs around town isn't that uncommon a thing, but the region you're in is unique and amazing. I got to visit it a couple weeks ago and was blown away by the number of bugs on Penn's.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Tlm28October 15th, 2007, 7:56 am
Posts: 1I am taking fly fishing 101 from the college where I work. I needed to understand the difference between free stone and limestone streams. The posts here have been more than helpful. Thank you all, Tracy
GeneOctober 15th, 2007, 11:33 am
Posts: 107Konchu:

I won't go into a stream discussion limestone versus freestone because too many things seem to get lost when it comes to science on this forum versus opinion. However, the basic types of limestone streams as described by Gonzo are good enough for government work if you know what I mean.

The real difference between true limestone spring creeks whether they are the Letort, Big Spring, The Itchen, The Test, or Armstrong and so forth results from three major properties: 1) extremely limited temperature range 2)limited substrate types and 3)limited variety of current speeds. As an aquatic entomologist you know that this limits diversity because it limits the available types of microhabitat and niches etc. Every stream type has a unique biogeochemical signature which gives it a bigeochemical footprint. The footprint of these streams is basically the same. The insects are also basically the same whether you find E. invaria in one or it's Western or English counterpart. Simply put similar biogeocemical signatures produces basically the same footprint (astoundingly the colors of the insects are also the same or very close).

The macroinvertebrate population found in limestone spring creeks versus freestone streams or any other comparison obey Thienermann's rules for stream diversity:

1) the greater the diversity of the conditions in a locality the larger is the number of species which make up the biotic community.
2) The more conditions in a locality deviate from normal, and hence from the normal optima of most species, the smaller is the number of species which occur there and the greater the number of individuals of each species which do occur.
3)The longer a locality has been in the same condition the richer is its biotic community and the more stable it is.

These spring creeks are very rich but all of them have a few dominant species which make sense. They may have more than one generation due to the constant temps and it appears much harder for other insect populations to colonize them as compared to other freestone or limestone influenced streams. Streams like Penns Creek which are limestone influenced have a tremendous variety (or diversity of species) because they have a tremendous variety of environmental conditions such as temperature range, substrate size, current speed and even water chemistry. Once again a perfect match for Thienermann's rules for stream diversity. True spring creeks are basically controlled almost entirely by sunlight.

The problem with streams like Penns Creek is that the environment is very rough on the fish. You don't get a lot of very large trout in Penns due to the summers and sometimes winters. In streams like Big Spring, the Letort etc. the fish grow quick and large and all year because of the constant water temps, massive food supply and quality of water.

The streams limit the types of macroinvertebrates found there for all of the above reasons including certain stoneflies, and caddis which require specific substate and current speeds and some macroinvertebrats which seem to thrive in more neutral or acid waters such as Baetisca.

tight lines

DanoOctober 15th, 2007, 6:47 pm
Vanderbilt, Michigan

Posts: 101

I won't go into a stream discussion limestone versus freestone because too many things seem to get lost when it comes to science on this forum versus opinion. However, the basic types of limestone streams as described by Gonzo are good enough for government work if you know what I mean.

Wow, that was rude...and transparent; you reply to a 4 month old post, knock the forum, take a potshot at an individual, then proceed to do what you said you wouldn't do....


Eventually, all things merge into one...and a river runs through it.
GeneOctober 15th, 2007, 10:11 pm
Posts: 107Dano:

First of all I don't know you but your post has nothing to do with what was written. Good enough for government work is a standard used in much of environmental consulting and just means you didn't have to go into great detail because you didn't need to (and there would be greater associated cost to it and no one would use it anyway). I'm sure Gonzo could have gone into much greater detail if he wanted to because I know him from the Fly fishers' of Harrisburg Luncheons and I know he has heard many scientific papers and data presented over the years and I know he has a pretty good scientific understanding of what he talks about.

As far as my comment I stand by it. I come from the scientific community and the first law is: read and search the literature which unfortunately too many people won't do. Also, it pays to have many years experience in the field if one is to pontificate on it.

The comment to Konchu was nothing more than a brief scientific explanation of HIS Question because unless you've worked in true spring creeks it's different world biologically. Furthermore, your statement that I said one thing and proceeded to do it anyway is your interpretation of the reply.

If I wanted to delineate the differences between limestone and freestone streams I could have done that but I didn't. As I said what Gonzo put out is good enough for government work and is concise enough in both a scientific and piscatorial sense. As far as answering the post after 4 months...well someone just posted again ...what's that have to do with anything!

As far as knocking the forum....I didn't do that at all. I knocked the idea that scientific opinion backed by facts and data .....that's one thing..but because you have an opinion and dress it up doesn't make it science. We have a government that does that every day! And that's why are streams are taking such a beating!

Oh, by the way there must be something to my posts because I get emails on this forum and personal ones on my websites thanking me for trying to keep the discussion flowing along scientific venues rather than just opinions watering down the discussion too much. I think maybe because the people who post here like the scientific stuff on this site which I think is great and is lacking on other sites. If they just wanted opinion without science there are tons of fly fishing sites which offer that.

So have a beer and chill I'm sure your a good enough guy. I've given up trying to please everyone and one final note to Shawn: your question on the differences between limestone streams and freestone streams is a good one because even many books on aquatic science don't address it properly. Furthermore, the amount of misinformation on them both from a fishing and a scientific one is unbelievable.

tight lines and cold beers


Golf is for people who don't have the skills, imagination, or intelligence to fly fish~

GONZOOctober 20th, 2007, 10:04 am
Site Editor
"Bear Swamp," PA

Posts: 1681

I've been on a self-imposed exile from this site while I was moving to the Lehigh Valley to start a new job. This seemed like a good opportunity to resume posting because, even in my absence, I seem to have been inadvertently involved in a minor, but unfortunate conflict.

I hate to see fly fishers get off on the wrong foot because of mistaken impressions. Trust me when I say that I take Gene's reference to my old post as "good enough for government work" as a compliment. Gene is an experienced fly fisher, a dedicated conservationist, and his research on Cumberland Valley spring creeks has been both eye-opening and very useful to me.

I think fly fishers can be forgiven if their opinions aren't always grounded in good science, but Gene is right when he says that research into the scientific literature can be quite valuable and can keep us from jumping to goofy conclusions based on anecdotal evidence. (Of course, researching scientific papers also means wading through lots of scientific jargon. That can get quite deep at times, and it's easy to get in over your head.) I also find the scientists that post here to be a really wonderful resource, and that is one of the things that truly sets this site apart from most of the others.

So, Dano, welcome to the site, and thanks for leaping to my defense, but no defense was necessary.

GeneOctober 20th, 2007, 4:04 pm
Posts: 107Gonzo:

Thanks Gonzo..I think you knew where I was coming from on this. I'm sure Dano is a good guy...I don't have any problem with his post; he meant well. I'm trying to move too. It's getting too expensive around here. Is anything cheaper in the Lehigh area? I'm actually looking for Carlisle which is way cheaper than Waynesboro? The rents and home prices are a joke even though there are a ton of places in foreclosure and lots of homes on the market that no one can sell!

I have to get out of here because it's cramping my fishing and research. But the fishing...well if we don't get rain soon...I may look for a Native American (or to be politically incorrect an Indian)to do some type of rain dance or something. You can literally walk across the freestoners around here without getting your ankles wet.

Hope your move and a new job will be fruitful.

Tight lines and dancing nymphs


GONZOOctober 20th, 2007, 6:48 pm
Site Editor
"Bear Swamp," PA

Posts: 1681
Hi Gene,

I wish I could report that things were cheaper here, but aside from a local Hess station that seems determined to drive its Sunoco competition out of business by offering the best gas prices in the area, I can't. I know what you mean, though. With all the fuss about the housing bubble bursting, you'd think the prices would drop. People are sitting on a lot of overpriced properties that aren't moving. I think everyone is still trying to get their slice of the housing pie-in-the-sky after it's already been eaten.

I also know what you mean about the pathetic water levels. About the only thing that's made my not being able to fish since August tolerable is the lack of water--it's depressing.


TroutnutOctober 20th, 2007, 6:55 pm
Bellevue, WA

Posts: 2734
At least your rivers aren't frozen over yet. :)
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
GONZOOctober 20th, 2007, 7:51 pm
Site Editor
"Bear Swamp," PA

Posts: 1681
Hey . . . no complaints allowed from the Alaskan Department! After all, the long dark winter you're facing is the price you have to pay for moving to angling nirvana. Look on the bright side, Jason--you might get to ski before I get to fish again! -Gonzo
TroutnutOctober 20th, 2007, 9:38 pm
Bellevue, WA

Posts: 2734
Good point. :)
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
IEatimagoOctober 22nd, 2007, 7:21 am
Spring Mills, PA

Posts: 97
its been like 80' all october, this is garbage.
i never thought id complain about 80 degree weather, but i didnt leave the west for nothing!

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