Snakeheads in Philly area

[tomgamber]

Brook trout in PA were displaced by loss of habitat, not by competition from browns or rainbows.

this is not an entirely true statement.

 

[silverfox]

Brook trout in PA were displaced by loss of habitat, not by competition from browns or rainbows.

Where did you read this?

I'd really like a source for that statement if you're going to simply say it with no supporting evidence. In the meantime;

From the EBTJV rangewide assessment (https://easternbrooktrout.org/about/reports/eastern-brook-trout-status-and-threats (2006)/view);

"Non-native fish rank as the largest biological threat to brook trout."

In Pennsylvania specifically;

"Regional experts cited competition and predation from brown trout as the third highest ranked impact across the state. Urbanization and associated road sedimentation ranked among the top five disturbances statewide."

In a ranked list, Poor Land Management, High Water Temperature, Brown Trout, Sedimentation (Roads), and Urbanization were listed, in that order, as top disturbances to brook trout in Pennsylvania.

Beyond that, the notion that brook trout were wiped out and then brown trout were introduced with no further impact defies logic and scientific literature.

 

[Fish Sticks]

Brook trout in PA were displaced by loss of habitat, not by competition from browns or rainbows.

This is an example of where PA fish and boat has failed to educate its anglers. So many people believe this sadly. When you talk to fisheries scientists who have their PhD in this it’s like a no brainer that invasive trout species are a top 3-4 issue.It’s just like saying the sky is blue to them. And it’s actually something we can address easily because we pay around 12.4 million a year to stock them.

 

[Fish Sticks]

This is an example of where PA fish and boat has failed to educate its anglers. So many people believe this sadly. When you talk to fisheries scientists who have their PhD in this it’s like a no brainer that invasive trout species are a top 3-4 issue.It’s just like saying the sky is blue to them. And it’s actually something we can address easily because we pay around 12.4 million a year to stock them.

Those stocked invasive trout have been shown to limit bidirectional gene flow of brook trout genes that are important for healthy meta population genetics. We will spend 20k to take out a bad culvert(which is worth it) but we won’t stop dumping in browns and rainbows that have been shown to act as a barrier in a similar way. If a brook trout gets blocked by a culvert, eaten by a brown/rainbow, or won’t venture into habitat occupied by invasive trout the end result is same.

 

[moon1284]

It's pretty simple biology. Habitat destruction has caused way more problems to brook trout populations than the introduction of brown and rainbow trout.

 

[moon1284]

Where did you read this?

I'd really like a source for that statement if you're going to simply say it with no supporting evidence. In the meantime;

From the EBTJV rangewide assessment (https://easternbrooktrout.org/about/reports/eastern-brook-trout-status-and-threats (2006)/view);

"Non-native fish rank as the largest biological threat to brook trout."

In Pennsylvania specifically;

"Regional experts cited competition and predation from brown trout as the third highest ranked impact across the state. Urbanization and associated road sedimentation ranked among the top five disturbances statewide."

In a ranked list, Poor Land Management, High Water Temperature, Brown Trout, Sedimentation (Roads), and Urbanization were listed, in that order, as top disturbances to brook trout in Pennsylvania.

Beyond that, the notion that brook trout were wiped out and then brown trout were introduced with no further impact defies logic and scientific literature.

Read your list. Poor land management and water temperature = habitat problem. Sedimentation and urbanization = habitat problem. Brown trout are 3rd out of 5 on the list and 4 of the 5 are habitat related.

Brown trout were introduced because the ST habitat was decimated by industry. Right now, I agree that there are streams could have more brook trout if there were no Brown trout. But if Brown trout weren't introduced it's questionable at best that native brook trout would have naturally repopulated these streams. Look at Washington state and Maine for two states with hardly any wild Brown trout. I can't speak for Washington, but in Maine big native brook trout are either in ponds or lakes, or a few large very remote river systems. Do you think that if browns weren't introduced to say Penns or the upper delaware that people would be catching 20 inch native brookies?

To say Brown trout are the main reason that there is such a disparity between the current and the historical range and population of ST defies all logic and science. Your source isn't saying that at all.

 

[lycoflyfisher]

Brown trout were introduced because the ST habitat was decimated by industry. Right now, I agree that there are streams could have more brook trout if there were no Brown trout. But if Brown trout weren't introduced it's questionable at best that native brook trout would have naturally repopulated these streams.

So where did the wild brook trout that exist today come from? Are you saying they were wiped out and only exist today due to fish of hatchery origin?

 

[silverfox]

Read your list. Poor land management and water temperature = habitat problem. Sedimentation and urbanization = habitat problem. Brown trout are 3rd out of 5 on the list and 4 of the 5 are habitat related.

Brown trout were introduced because the ST habitat was decimated by industry. Right now, I agree that there are streams could have more brook trout if there were no Brown trout. But if Brown trout weren't introduced it's questionable at best that native brook trout would have naturally repopulated these streams. Look at Washington state and Maine for two states with hardly any wild Brown trout. I can't speak for Washington, but in Maine big native brook trout are either in ponds or lakes, or a few large very remote river systems. Do you think that if browns weren't introduced to say Penns or the upper delaware that people would be catching 20 inch native brookies?

To say Brown trout are the main reason that there is such a disparity between the current and the historical range and population of ST defies all logic and science. Your source isn't saying that at all.

I didn't write that list. The EBTJV did. You seem unwilling to accept the fact that nonnative fish have contributed to declines in brook trout numbers across their native range.

"But if Brown trout weren't introduced it's questionable at best that native brook trout would have naturally repopulated these streams." What on earth are you basing this assumption on? Do you think brook trout mysteriously disappeared from the Letort and the only reason they don't live there now is because of industrial pollution from the turn of the century or some mysterious habitat or water quality problem?

Nobody is talking about big brook trout. No, I don't claim that if Penns creek was devoid of brown trout that there would be 20-inch wild native brookies. I never said that and never implied it. Would there be more brook trout in Penns creek than there is today? Probably, yes. Would tributaries to Penns Creek have more wild brook trout? Probably, yes. Would the average size of the fish be larger in Penns and its tributaries? Probably, yes.

"Washington state"? You realize brook trout aren't native to Washington state right?

Nobody said "brown trout are the main reason..." I stated that they're an issue, which they are.

 

[Fish Sticks]

Read your list. Poor land management and water temperature = habitat problem. Sedimentation and urbanization = habitat problem. Brown trout are 3rd out of 5 on the list and 4 of the 5 are habitat related.

Brown trout were introduced because the ST habitat was decimated by industry. Right now, I agree that there are streams could have more brook trout if there were no Brown trout. But if Brown trout weren't introduced it's questionable at best that native brook trout would have naturally repopulated these streams. Look at Washington state and Maine for two states with hardly any wild Brown trout. I can't speak for Washington, but in Maine big native brook trout are either in ponds or lakes, or a few large very remote river systems. Do you think that if browns weren't introduced to say Penns or the upper delaware that people would be catching 20 inch native brookies?

To say Brown trout are the main reason that there is such a disparity between the current and the historical range and population of ST defies all logic and science. Your source isn't saying that at all.

Maine has big time brown trout issues in more than a few places. And they have huge issues with invasive smallmouth, yellow perch, and many more as well so if your trying to say ME brookies not suffering from invasive species that’s incorrect. Ironically that’s why native fish coalition was formed in Maine because of how bad the invasive species problem is.

Yes the scientists in the studies never researched if you could grow a 20” brook trout in penns creek specifically. However, I never claimed that specifically either. This is the problem with ramped inability for people to separate fishing and conservation. If ya can’t grow a 20” brook trout in penns creek does that mean we just say screw the whole food web and the native crayfish, sculpins, darters, and macro invertebrates can just take the hit from invasive brown trout because we like how they take a fly? That’s a fishing mentality not a conservation one.

But since you mentioned it who says the 6-10” brookies you catch in penns from time to time couldn’t grow bigger if they were not in competition with brown trout? There are a lot of brook trout streams going into penns infested with invasive browns. There is a lot of research saying trout move downstream to take advantage of richer food sources, especially 3 seasons a year. There is also a lot of research saying brown trout prevent brook trout from occupying more favorable downstream habitat. If they weren’t there they wouldn’t be in completion for that food source and they would move downstream and grow bigger. Don’t believe me? Don’t care because it’s been proven already in this study where browns were removed and brookies reclaimed the stream and got bigger. Habitats wasn’t an issue when browns were removed I guess,huh.

(PDF) Long-term population demographics of native brook trout following manipulative reduction of an invader

PDF | Although laboratory studies have provided evidence for negative interactions between brook trout and brown trout, it is unknown how these... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

You have tunnel vision on water quality temp and physical habitat but have you ever stopped to think what if the brook trout themselves have been damaged genetically? How about instead of restoring just streams we restore their genetics back to closer to what they once were. We have all seen deliverance. Inbreeding is bad and we put these small populations on an island all lone in many cases forcing them to inbreed. This is where genetic rescue comes in. We can reverse inbreeding and it’s been shown to make larger more Fertile brook trout see for yourself.

Experimental test of genetic rescue in isolated populations of brook trout | Request PDF

Request PDF | Experimental test of genetic rescue in isolated populations of brook trout | Genetic rescue is an increasingly considered conservation measure to address genetic erosion associated with habitat loss and fragmentation. The... | Find, read and cite all the research you need on...

www.researchgate.net

So maybe you will look at penns creek differently because there is two very important reasons(backed by data) that says those brookies in penns are no where near their full potential in terms of a healthy population and would likely increase in size. I am not going to say how much because I have no clue but 20” is even way larger than average brown in penns creek. Instead of digging in with no data to support your statements maybe just acknowledge brook trouts conservation prospects should not be decided based on tackle shop talk.

 

[moon1284]

I didn't write that list. The EBTJV did. You seem unwilling to accept the fact that nonnative fish have contributed to declines in brook trout numbers across their native range.

"But if Brown trout weren't introduced it's questionable at best that native brook trout would have naturally repopulated these streams." What on earth are you basing this assumption on? Do you think brook trout mysteriously disappeared from the Letort and the only reason they don't live there now is because of industrial pollution from the turn of the century or some mysterious habitat or water quality problem?

Nobody is talking about big brook trout. No, I don't claim that if Penns creek was devoid of brown trout that there would be 20-inch wild native brookies. I never said that and never implied it. Would there be more brook trout in Penns creek than there is today? Probably, yes. Would tributaries to Penns Creek have more wild brook trout? Probably, yes. Would the average size of the fish be larger in Penns and its tributaries? Probably, yes.

"Washington state"? You realize brook trout aren't native to Washington state right?

Nobody said "brown trout are the main reason..." I stated that they're an issue, which they are.

You said non native fish are the biggest threat to brook trout in a post above. I'll agree to disagree here.

 

[moon1284]

Maine has big time brown trout issues in more than a few places. And they have huge issues with invasive smallmouth, yellow perch, and many more as well so if your trying to say ME brookies not suffering from invasive species that’s incorrect. Ironically that’s why native fish coalition was formed in Maine because of how bad the invasive species problem is.

Yes the scientists in the studies never researched if you could grow a 20” brook trout in penns creek specifically. However, I never claimed that specifically either. This is the problem with ramped inability for people to separate fishing and conservation. If ya can’t grow a 20” brook trout in penns creek does that mean we just say screw the whole food web and the native crayfish, sculpins, darters, and macro invertebrates can just take the hit from invasive brown trout because we like how they take a fly? That’s a fishing mentality not a conservation one.

But since you mentioned it who says the 6-10” brookies you catch in penns from time to time couldn’t grow bigger if they were not in competition with brown trout? There are a lot of brook trout streams going into penns infested with invasive browns. There is a lot of research saying trout move downstream to take advantage of richer food sources, especially 3 seasons a year. There is also a lot of research saying brown trout prevent brook trout from occupying more favorable downstream habitat. If they weren’t there they wouldn’t be in completion for that food source and they would move downstream and grow bigger. Don’t believe me? Don’t care because it’s been proven already in this study where browns were removed and brookies reclaimed the stream and got bigger. Habitats wasn’t an issue when browns were removed I guess,huh.

(PDF) Long-term population demographics of native brook trout following manipulative reduction of an invader

PDF | Although laboratory studies have provided evidence for negative interactions between brook trout and brown trout, it is unknown how these... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

You have tunnel vision on water quality temp and physical habitat but have you ever stopped to think what if the brook trout themselves have been damaged genetically? How about instead of restoring just streams we restore their genetics back to closer to what they once were. We have all seen deliverance. Inbreeding is bad and we put these small populations on an island all lone in many cases forcing them to inbreed. This is where genetic rescue comes in. We can reverse inbreeding and it’s been shown to make larger more Fertile brook trout see for yourself.

Experimental test of genetic rescue in isolated populations of brook trout | Request PDF

Request PDF | Experimental test of genetic rescue in isolated populations of brook trout | Genetic rescue is an increasingly considered conservation measure to address genetic erosion associated with habitat loss and fragmentation. The... | Find, read and cite all the research you need on...

www.researchgate.net

So maybe you will look at penns creek differently because there is two very important reasons(backed by data) that says those brookies in penns are no where near their full potential in terms of a healthy population and would likely increase in size. I am not going to say how much because I have no clue but 20” is even way larger than average brown in penns creek. Instead of digging in with no data to support your statements maybe just acknowledge brook trouts conservation prospects should not be decided based on tackle shop talk.

A couple things here. There are next to zero wild brown trout in Maine. About equal to the amount of wild rainbow trout in pa if you don't include rainbows from the upper delaware. Your argument that ST have decline in ME (even though there are hardly any BT, proves my point even further). You're making so many different arguments I can't keep track of what is what.

You mention genetics. I don't follow why the introduction of brown trout would affect the genetics of ST. In the odd event ST and BT reproduce you get sterile offspring.

If I'm using "tackle shop talk", you're using "Google search talk".

 

[Fish Sticks]

A couple things here. There are next to zero wild brown trout in Maine. About equal to the amount of wild rainbow trout in pa if you don't include rainbows from the upper delaware. Your argument that ST have decline in ME (even though there are hardly any BT, proves my point even further). You're making so many different arguments I can't keep track of what is what.

You mention genetics. I don't follow why the introduction of brown trout would affect the genetics of ST. In the odd event ST and BT reproduce you get sterile offspring.

If I'm using "tackle shop talk", you're using "Google search talk".

Why can’t you understand how invasive brown and rainbow trout would change brook trout genetics after over 100 years after all the articles I’ve shared. Did you read even the abstracts??? I said “ invasive trout are barriers to brook trout gene flow similar to bad culverts”. If the genes can’t move to different tributaries in the water shed and mix, picture what happens when humans can’t marry outside the family. doesn’t exactly make for healthy human beings. If a brown trout or rainbow eats a brook trout it can’t spread its genes to another population same effective outcome of getting stuck behind a culvert.

Your absolutely right I’m speaking in “google search” because I google searched the names of real subject matter experts in brook trout ecology years ago before I read their work and spoke with them about their work and now I am literally copying and pasting their findings into this discussion. You can tell them they don’t know what their talking about I’m sure they will abandon their work.

 

[silverfox]

You said non native fish are the biggest threat to brook trout in a post above. I'll agree to disagree here.

Do you mean this: ""Non-native fish rank as the largest biological threat to brook trout."

I didn't say that. It's in the EBTJV range-wide assessment report I posed the link to. Are you claiming to know better than a collective of scientists, biologists, and brook trout ecologists?

Eastern Brook Trout: Status and Threats (2006) — EBTJV

This technical report identifies where wild brook trout populations remain strong, where they are struggling and where they have vanished. Most importantly, it provides state and federal agencies, anglers and community leaders with the tools to identify local rivers and streams that are...

easternbrooktrout.org

 

[moon1284]

Do you mean this: ""Non-native fish rank as the largest biological threat to brook trout."

I didn't say that. It's in the EBTJV range-wide assessment report I posed the link to. Are you claiming to know better than a collective of scientists, biologists, and brook trout ecologists?

Eastern Brook Trout: Status and Threats (2006) — EBTJV

This technical report identifies where wild brook trout populations remain strong, where they are struggling and where they have vanished. Most importantly, it provides state and federal agencies, anglers and community leaders with the tools to identify local rivers and streams that are...

easternbrooktrout.org

View attachment 1641224656

Do you know the difference between a biological and an environmental factor?

I'll try and be as clear as I can. Loss of habitat is the number one reason the range and population of ST is what it is today compared to 150 years ago. There are other factors i.e. introduced trout, however the impact caused by introduced trout is miniscule compared to impact caused by habitat loss.

 

[moon1284]

Why can’t you understand how invasive brown and rainbow trout would change brook trout genetics after over 100 years after all the articles I’ve shared. Did you read even the abstracts??? I said “ invasive trout are barriers to brook trout gene flow similar to bad culverts”. If the genes can’t move to different tributaries in the water shed and mix, picture what happens when humans can’t marry outside the family. doesn’t exactly make for healthy human beings. If a brown trout or rainbow eats a brook trout it can’t spread its genes to another population same effective outcome of getting stuck behind a culvert.

Your absolutely right I’m speaking in “google search” because I google searched the names of real subject matter experts in brook trout ecology years ago before I read their work and spoke with them about their work and now I am literally copying and pasting their findings into this discussion. You can tell them they don’t know what their talking about I’m sure they will abandon their work.

You're correct, when brown and rainbow trout eat ST, the ST cannot pass on their genes and continue to evolve.

What you're missing is that habitat loss has had and continues to have a much stronger negative impact on ST than the introduction of BT and RT. The decline of ST started before BT and RT were introduced.

For the record I don't think there should be fish stocked over native trout. But stocking over native trout is the exception not the rule.

 

[Fish Sticks]

Do you know the difference between a biological and an environmental factor?

I'll try and be as clear as I can. Loss of habitat is the number one reason the range and population of ST is what it is today compared to 150 years ago. There are other factors i.e. introduced trout, however the impact caused by introduced trout is miniscule compared to impact caused by habitat loss

(PDF) Long-term population demographics of native brook trout following manipulative reduction of an invader

PDF | Although laboratory studies have provided evidence for negative interactions between brook trout and brown trout, it is unknown how these... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

Except in this study when apparently the modern day habitat was fine for the brook trout once the brown trout were manually removed and the brook trout immigrated back downstream, reclaimed it and grew larger in size of course. There are no absolutes but in many cases on state game land or state parks we are still losing native brook trout in completely forested streams with good physical habitat to invasive trout. The invasive species issue has been HUGELY underestimated by anglers but not by the conservation community “largest biological threat”. The research I’ve shared on this thread showing brook trout can survive warmer water temps without brown trout pushing them out of thermal refuge is happening in todays habitat. The study showing they take advantage of larger downstream habitat and grow larger if brown trout are not present is happening in todays habiat. Saying non native trout have a minuscule effect compared to habitat is extremely misleading because it’s not about putting streams back to how they were 400 years ago because can’t, humans are here. With the habitat we have currently, not stocking and removing invasive trout where it makes sense to do so is one of the most cost saving and impactful things we can do for native brook trout respectively with the habitats that we have today. I’m not trying to tell you to eliminate brown trout in all of PA, they are here to stay. I don’t hate brown trout or rainbow trout either I think they are beautiful creatures and I respect them and wish things were going better for them In their native ranges. I enjoy fishing for them both even. I just wish that anglers and PA fish and boat could manage for native brook trout in a few places where from a conservation standpoint they could have genetically diverse large healthy populations. Kettle creek above the Alvin bush dam could have native hellbenders again and l a full complement of native fish species if it wasn’t stocked to death promoting wild brown trout( they didn’t swim there from Scotland). But in this state we cannot even give up ONE high quality watershed to native brook trout and their full complement of native fish/aquatic organisms they evolved with and interact with in a sustainable way. I wish in just one watershed we could manage an entire ecosystem instead of just for one or two invasive sport fish to the detriment of the entire cold water ecosystem.

 

[silverfox]

Do you know the difference between a biological and an environmental factor?

I'll try and be as clear as I can. Loss of habitat is the number one reason the range and population of ST is what it is today compared to 150 years ago. There are other factors i.e. introduced trout, however the impact caused by introduced trout is miniscule compared to impact caused by habitat loss.

You keep moving the goalposts.

You said; "You said non native fish are the biggest threat to brook trout in a post above. I'll agree to disagree here." That's not what I posted. You're not quoting what I write, you're trying to twist what I write into something else. I posted a direct quote from a range-wide study.

Now you're questioning whether I understand the difference between biological and environmental? What does that have to do with anything? You said you disagree that "Non-native fish rank as the largest biological threat to brook trout.". So please explain how the authors of the EBTJV report are wrong.

You never said "Loss of habitat is the number one reason the range and population of ST is what it is today" before your last post. I wouldn't argue that point and I never said that wasn't the case. You claimed, with absolutely nothing to back it up, "Brook trout in PA were displaced by loss of habitat, not by competition from browns or rainbows.". The "not by competition from browns or rainbows" is patently false and is backed up by numerous scientific studies.

"however the impact caused by introduced trout is miniscule [sic] compared to impact caused by habitat loss."
I'd say ranked #3 out of 5 isn't "minuscule" in a generalized list of threats. You seem really committed to downplaying the negative impacts of nonnative fish on brook trout in the face of science that says the opposite while providing zero actual evidence of your claims.

Going back to your first comment which you never explained, "Neither Brown trout or rainbow trout are invasive in PA.". You've now admitted that introduced species ARE in fact a threat to brook trout, even if "minuscule". That, by definition, is an invasive species.

 

[moon1284]

(PDF) Long-term population demographics of native brook trout following manipulative reduction of an invader

PDF | Although laboratory studies have provided evidence for negative interactions between brook trout and brown trout, it is unknown how these... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

Except in this study when apparently the modern day habitat was fine for the brook trout once the brown trout were manually removed and the brook trout immigrated back downstream, reclaimed it and grew larger in size of course. There are no absolutes but in many cases on state game land or state parks we are still losing native brook trout in completely forested streams with good physical habitat to invasive trout. The invasive species issue has been HUGELY underestimated by anglers but not by the conservation community “largest biological threat”. The research I’ve shared on this thread showing brook trout can survive warmer water temps without brown trout pushing them out of thermal refuge is happening in todays habitat. The study showing they take advantage of larger downstream habitat and grow larger if brown trout are not present is happening in todays habiat. Saying non native trout have a minuscule effect compared to habitat is extremely misleading because it’s not about putting streams back to how they were 400 years ago because can’t, humans are here. With the habitat we have currently, not stocking and removing invasive trout where it makes sense to do so is one of the most cost saving and impactful things we can do for native brook trout respectively with the habitats that we have today. I’m not trying to tell you to eliminate brown trout in all of PA, they are here to stay. I don’t hate brown trout or rainbow trout either I think they are beautiful creatures and I respect them and wish things were going better for them In their native ranges. I enjoy fishing for them both even. I just wish that anglers and PA fish and boat could manage for native brook trout in a few places where from a conservation standpoint they could have genetically diverse large healthy populations. Kettle creek above the Alvin bush dam could have native hellbenders again and l a full complement of native fish species if it wasn’t stocked to death promoting wild brown trout( they didn’t swim there from Scotland). But in this state we cannot even give up ONE high quality watershed to native brook trout and their full complement of native fish/aquatic organisms they evolved with and interact with in a sustainable way. I wish in just one watershed we could manage an entire ecosystem instead of just for one or two invasive sport fish to the detriment of the entire cold water ecosystem.

Too long to read you win

 

[moon1284]

You keep moving the goalposts.

You said; "You said non native fish are the biggest threat to brook trout in a post above. I'll agree to disagree here." That's not what I posted. You're not quoting what I write, you're trying to twist what I write into something else. I posted a direct quote from a range-wide study.

Now you're questioning whether I understand the difference between biological and environmental? What does that have to do with anything? You said you disagree that "Non-native fish rank as the largest biological threat to brook trout.". So please explain how the authors of the EBTJV report are wrong.

You never said "Loss of habitat is the number one reason the range and population of ST is what it is today" before your last post. I wouldn't argue that point and I never said that wasn't the case. You claimed, with absolutely nothing to back it up, "Brook trout in PA were displaced by loss of habitat, not by competition from browns or rainbows.". The "not by competition from browns or rainbows" is patently false and is backed up by numerous scientific studies.

"however the impact caused by introduced trout is miniscule [sic] compared to impact caused by habitat loss."
I'd say ranked #3 out of 5 isn't "minuscule" in a generalized list of threats. You seem really committed to downplaying the negative impacts of nonnative fish on brook trout in the face of science that says the opposite while providing zero actual evidence of your claims.

Going back to your first comment which you never explained, "Neither Brown trout or rainbow trout are invasive in PA.". You've now admitted that introduced species ARE in fact a threat to brook trout, even if "minuscule". That, by definition, is an invasive species.

K you win

 

[pcray1231]

I think it's pretty obvious habitat loss and brown trout do not act in isolation. It's a 1, 2 punch.

Moon, these guys are saying that the brown trout issue is generally a genetic argument. Brookie streams are all fine and good but it's hard for genetics to transfer from one brookie stream to another, which limits biodiversity and over time makes a given population more susceptible to environmental events like a low pH spike or a high temperature.

Think of a watershed. Maybe originally the main stem and 10 tributaries had interconnected brookie populations, which regularly shuffled enough DNA around to make a rather diverse, resistant genetic population. Some fish handle warmer temps better, some handle acid better, etc. In the event of a drought, yeah, maybe a lot of fish died but there are plenty that survive near enough by to repopulate quickly, and the repopulation occurs from fish that are more resistant to the bad thing that just happened. A yearly cycle was the main stem warming, and all those fish going up the tribs, then back down in winter, and maybe up a different trib next summer. This was extremely common and well known on bigger waters like Pine, Kettle, and yes, PENNS. To the point that reading anglers of the day considered the migratory travelers to be almost separate population than the residents that stayed in the headwaters year round. This was a driver of genetic diversity in all of those streams.

Land use issues, environmental factors, well, they warmed up the main stem a little, and those 10 tribs are down to 5. And hey, brown trout took over the main stem and the lower portions of several of those tribs. We just lost 5 tribs due to environmental factors. As a fisherman we can look and say, yep, environmental issues are the real problem of why we lost those tribs, and we kind of like fishing for browns in the main stem, so it's not a loss. Our 5 remaining brookie streams are doing just fine. It'd be nice to get a few of those tribs back but all is well with both brookies and browns, right? But they are now more isolated. Not as interconnected with the neighboring streams populations. And from a biologists point of view, who is less concerned about how well it fishes in 5 years and more thinking about whether that brookie population will still exist in 300 years. Isolated populations are in DANGER. Not saying a brookie NEVER goes down to the main stem and up a different stream. But it's rarer, they don't do so in large numbers. So each of those brookie streams is more isolated, genetically speaking, less diverse, and becoming more so. A population of inbreds. Isolated populations are genetically inferior and less able to handle an environmental disruption, less able to compete with the invasives, etc.

The immediate cause of the decline will be environmental. But an isolated population will be less capable of coping with that problem. No different than any other animal. Isolating populations is not good for the long term survivability of a species.