Brook Trout Myths Podcast

Fish Sticks

Fish Sticks

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Recently I was a guest of the fly flyfishing consultant podcast for an episode titled “Brook trout myths and urban legends” it just became available yesterday.


As many of you know I have been reviewing the literature on native brook trout (ecology, conservation genetics, non native trout invasion biology), discussing the literature/ native brook trout management with a few different PhDs, attending scientific workshops within the field of brook trout conservation genetics and ecology. My goal was to educate myself but mostly to create an educated angling public that can start to hold it’ fisheries managers responsible for this species of greatest conservation need accountable here in PA.

Enjoy this episode where I put together a light literature review for you all on many things relevant to the managment of our state fish with some PA context, examples, and implications.

Thanks to Rob for letting me share the wonderful research being done by fisheries scientists with you all!

 
wcosner2

wcosner2

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Recently I was a guest of the fly flyfishing consultant podcast for an episode titled “Brook trout myths and urban legends” it just became available yesterday.


As many of you know I have been reviewing the literature on native brook trout (ecology, conservation genetics, non native trout invasion biology), discussing the literature/ native brook trout management with a few different PhDs, attending scientific workshops within the field of brook trout conservation genetics and ecology. My goal was to educate myself but mostly to create an educated angling public that can start to hold it’ fisheries managers responsible for this species of greatest conservation need accountable here in PA.

Enjoy this episode where I put together a light literature review for you all on many things relevant to the managment of our state fish with some PA context, examples, and implications.

Thanks to Rob for letting me share the wonderful research being done by fisheries scientists with you all!

You make a lot of excellent points and the podcast was a great listen! I recently completed an undergrad thesis on trout in Pennslyvania so it was nice to hear many of my points reiterated.

I worked with TU this past summer and it is amazing how tough these brookies are. We surveyed AMD streams where remediation took place and the stream is still bright red, the bottom covered with heavy metal deposits, and there are probably 3 insect species alive but 10-inch brook trout are just swimming along, doing their thing.

I also remember the study about conducting habitat improvements on brook trout streams and having browns take over. While this can absolutely happen, up in the Kettle Creek watershed, I have seen habitat improvement where browns are definitely present but it seems like the brook trout are using and thriving in the newly constructed habitats. Some of these habitat improvements didn't add incredible holes or habitat from an angler's perspective but they just created a few pockets that seem better suited to brook trout compared to larger, deeper holes that brown trout would take over. Obviously, there are many factors going into the consequences of habitat restoration. Wondering if you have any more thoughts on habitat improvements and if there are any contradictory studies about them.
 
Fish Sticks

Fish Sticks

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You make a lot of excellent points and the podcast was a great listen! I recently completed an undergrad thesis on trout in Pennslyvania so it was nice to hear many of my points reiterated.

I worked with TU this past summer and it is amazing how tough these brookies are. We surveyed AMD streams where remediation took place and the stream is still bright red, the bottom covered with heavy metal deposits, and there are probably 3 insect species alive but 10-inch brook trout are just swimming along, doing their thing.

I also remember the study about conducting habitat improvements on brook trout streams and having browns take over. While this can absolutely happen, up in the Kettle Creek watershed, I have seen habitat improvement where browns are definitely present but it seems like the brook trout are using and thriving in the newly constructed habitats. Some of these habitat improvements didn't add incredible holes or habitat from an angler's perspective but they just created a few pockets that seem better suited to brook trout compared to larger, deeper holes that brown trout would take over. Obviously, there are many factors going into the consequences of habitat restoration. Wondering if you have any more thoughts on habitat improvements and if there are any contradictory studies about them.
Very cool PM me your thesis I’d love to read it. What are your career plans?

Yea there are whole counties in PA i feel like mostly full of waters like that, i always wonder what they eat because there are some big brookies in those waters with no macros.

Yea the concerns about habitat work in sympatric brook/non native trout streams have been there for a while based on secondary observations on presence of brown trout from some of Hoxmeir and Deiterman’s work and Fausch and White showing brown trout displace brook trout from habitat in 1981. More recently Huntsman, Trego and the pine creek case study in wisconsin have confirmed this concern. I have not seen anything very definitive on how to prevent this yet besides removal. The pine creek case study referenced that brown trout are the highest users of over head cover of the three species(i have to see where that came from). They felt brook trout dropping 70% and brown trout increasing 3150% post restoration may have been due to large deep pools with overhead cover from root-wads and lunker bunkers giving the browns an advantage. I have talked with PhD’s about this and i have been told that removal obviously most definitive option if feasible but thats usually smaller systems above barriers. If removal can’t be done which will be majority of situations in bigger water with no barrier I would think, thats where I have not seen a ton of guidance published. Some think that creating habitat for young of the year/smaller trout might be safest for example shallower pools lots of shallow side channels ect. But I would love to see more research on what your options are to try and prevent the projects from giving browns the upper hand/harming the brookies, if any,when your dealing with sympatric populations in waterways not amenable to removal. I’m very interested in what legacy sediment removal BUT with tree plantings/forested wetlands would result in. I have a suspicion that a drift less area research article i read an abstract on it may contain some info but inhave to diy into the article and go through results and discussion.
 
Fish Sticks

Fish Sticks

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Obviously, there are many factors going into the consequences of habitat restoration. Wondering if you have any more thoughts on habitat improvements and if there are any contradictory studies about them.

The above article documents brook trout extirpating browns. An article like this may potentially contain some information surrounding what caused base flows to increase(which was felt to be a factor) that could highlight additional research questions/gaps that could be pursued to inform future restoration? It says that this occurred without “direct management” but its behind a pay wall. I need to get access.

I found another link in the past to the same article with a little more information about it that made it sound like Ag BMP’s or activities that improved ground water recharge may have been implemented, hence the work “direct”. Id have to get access to the paper to find out, it will take me a few days to get a copy from someone with access. But this is why I mentioned an interest in forested legacy sediment projects because increased groundwater recharge would theoretically influence base flows as well if I am not mistaken.

Id be really hesitant to say the shift to brook trout in the attached research was due to purely temperature changes because on the pine creek case study I’ve posted before the stream temps were way south of required/preferred range of native brook trout and it went from 96 % brookies pre construction to concerns about loosing them entirely 8 years post construction despite clean cold water. But again i’m a lay person so if I don’t read it directly, hear at a conference from an expert, or see on NGO, federal agency, or academic institution I’m not going to try to draw any conclusions with certainty.

It would be nice to read this article in entirety and get a subject matter experts assessment of both it and your question.

This stuff is so complicated and many people try to draw simple conclusions about water quality/temp in my experience. However, there are brook trout streams out there apparently that seem to be Invasion proof to brown trout with no apparent reason why.
 
silverfox

silverfox

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This is just my opinion based on reading a lot of papers and what I've seen firsthand. I think in a lot of these species shifts, an important variable is the population density for each species when some significant habitat impact occurs. In MD for example, there is a tiny population of browns that seems to come and go further up in the USR watershed. They never seem to take hold. That could be due to a warm year knocking the brook trout population down to a level where the browns gain a slight advantage that year. Conversely, if you've got a strong population of brown trout, and a few brook trout holding on, it will be difficult for the brook trout to recover unless there's some impact to the brown trout population that might give them an edge.

There are varying degrees of sympatry. Combine those population size variables with other environmental variables, and it will vary greatly by case whether one species dominates another.

If I recall, that Hoxmeir/Deiterman paper suggested a bad brook trout YOY survival year due to environmental disturbance could tip the scales. That might happen in either direction with either species. It could swing back and forth depending on which species is disturbed the most in that particular year.

I don't think it's a stretch to think that any major habitat disturbance other than a flood or drought could trigger that outcome. Natural disasters or well-intentioned humans with backhoes could theoretically cause enough of a disturbance to habitat and a reshuffling in habitat use to impact population density and trigger a species shift.
 
Fish Sticks

Fish Sticks

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This is just my opinion based on reading a lot of papers and what I've seen firsthand. I think in a lot of these species shifts, an important variable is the population density for each species when some significant habitat impact occurs. In MD for example, there is a tiny population of browns that seems to come and go further up in the USR watershed. They never seem to take hold. That could be due to a warm year knocking the brook trout population down to a level where the browns gain a slight advantage that year. Conversely, if you've got a strong population of brown trout, and a few brook trout holding on, it will be difficult for the brook trout to recover unless there's some impact to the brown trout population that might give them an edge.

There are varying degrees of sympatry. Combine those population size variables with other environmental variables, and it will vary greatly by case whether one species dominates another.

If I recall, that Hoxmeir/Deiterman paper suggested a bad brook trout YOY survival year due to environmental disturbance could tip the scales. That might happen in either direction with either species. It could swing back and forth depending on which species is disturbed the most in that particular year.

I don't think it's a stretch to think that any major habitat disturbance other than a flood or drought could trigger that outcome. Natural disasters or well-intentioned humans with backhoes could theoretically cause enough of a disturbance to habitat and a reshuffling in habitat use to impact population density and trigger a species shift.
I have heard manuscripts refer to that density dependent resistance to invasion called “Biotic resistance”. Which might be why studies like Mark Kirk et al’s showed brook trout are 12x more likely to be found in that study in PA streams when a barrier was present between nearest brown trout stocking location. If you keep stocking brown trout that ratio of brown to brook trout is probably skewed towards invasion. I have read that stocking brown trout increased “propagule pressure”(also called “introduction effort”) which furthers stage of invasion and increases numbers of brown trout that can overwhelm brook trout biotic resistance.

This begs the question are there some streams out there that if stocking was ceased removal of brown trout may not even be necessary? If there is a shift in ratio when stocking stops will there be a return of biotic resistance?
 
silverfox

silverfox

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I have heard manuscripts refer to that density dependent resistance to invasion called “Biotic resistance”. Which might be why studies like Mark Kirk et al’s showed brook trout are 12x more likely to be found in that study in PA streams when a barrier was present between nearest brown trout stocking location. If you keep stocking brown trout that ratio of brown to brook trout is probably skewed towards invasion. I have read that stocking brown trout increased “propagule pressure”(also called “introduction effort”) which furthers stage of invasion and increases numbers of brown trout that can overwhelm brook trout biotic resistance.

This begs the question are there some streams out there that if stocking was ceased removal of brown trout may not even be necessary? If there is a shift in ratio when stocking stops will there be a return of biotic resistance?
Right. Here's a good summary of a lot of the points you brought up in the podcast, and here.

 
Fish Sticks

Fish Sticks

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Right. Here's a good summary of a lot of the points you brought up in the podcast, and here.

Nice find, seems like the majority of the people in the conservation forum here are not the only ones who think C and R would have a worthwhile benefit, esp for the individuals who move. The article also mentions projects attract fishermen who want to keep fish, thats true and i think alot of the project sites on kettle are no exception to that.

Control of fishing related mortality. Mortality associated with recreational and sustenance fishing can contribute substantially to the dynamics of sport fish populations. Common methods for reducing fishing mortality include catch-and-release regulations and restrictions on fishing tackle. Unfortunately very little is known about the effectiveness of fishing regulations in restoring brook trout populations. Marschall and Crowder (1996) used population models to demonstrate that even under strong harvest-induced mortality of larger fish, brook trout populations were unlikely to be extirpated from a particular stream. It is generally believed that brook trout are relatively resistant to fishing related impacts due to their short life cycle and density-dependent survival and growth of brook trout populations (Grossman et al. 2010). Populations that exhibit strong density-dependence are able to compensate for fishing related mortality through reduced natural mortality and increased growth rates and fecundity. However, to our knowledge there are no published studies that have documented compensatory dynamics in brook trout populations. The effects of harvest in combination with other factors (i.e. physical and chemical degradation, stochastic events) most likely result in population declines that are far more drastic than projected by such deterministic population models. Also, individual brook trout that exhibit more fluvial life history traits (e.g., highly mobile, delayed maturity, larger size, longer-lived) may be highly susceptible to angler harvest, and loss of these individuals from a population may have a disproportionate effect on overall population productivity.”
 
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troutbert

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However, there are brook trout streams out there apparently that seem to be Invasion proof to brown trout with no apparent reason why.
Are there particular PA streams you have in mind?

In PA the reasons are usually pretty apparent. The streams that hold only brook trout, no browns, are usually infertile, low pH streams. Because of acid mine drainage or infertile geologies + acid precipitation. Where this is the case, even large (70 feet wide) and warm (80F in summer) streams can hold only brookies, no browns. Brookies are more tolerant of low pH conditions than brown trout.

In the more fertile freestone drainages, the brown trout are present high up into smallish streams. But in the very upper end, where the streams are quite small, it's often entirely brook trout.

The reasons are that very high up in freestone drainages, the pH is usually lower. And the very small streams often have shallow habitat, which favors brook trout not browns. And the very small freestone streams are vulnerable to severe droughts, which can dry up long stretches of the streams, with only a few scattered shallow pools. A PA fisheries biologist said their surveys show that the brook trout survive severe droughts better than browns.

Also, high up tbe water temps are cold, because that's where the water is coming out of the ground. In some parts of northern PA groundwater is 48F. Cold water favors brookies over browns for reproduction.

Regarding barriers. Where natural falls occur, that can be a barrier to passage. But in many cases people have stocked trout above falls. In PA you can generally assume that everything has been stocked.

Falls often occur at a geology bedrock boundary, where the stream is flowing first over a hard (infertile) rock, then flows onto a softer (more fertile) rock layer. The stream carves down into the soft layer, which is what creates the vertical drop.

Often the brown trout/ not brown trout division occurs where the bedrock changes, which changes the water chemistry from less fertile, lower pH upstream, to more fertile, higher pH downstream.

So, sometimes you will find brown trout below falls, but no brown trout above the falls. It might appear that it's because of the physical barrier, but in many cases that may be a water pH thing.

In infertile drainages, falls are often the dividing line between brook trout below the falls and no fish of any kind above the falls. For the same reason. Above the falls the pH is so low that no fish can survive there. But below the falls the water is flowing over a more fertile rock layer and receiving groundwater from the lower rock layer.
 
Fish Sticks

Fish Sticks

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Are there particular PA streams you have in mind?

In PA the reasons are usually pretty apparent. The streams that hold only brook trout, no browns, are usually infertile, low pH streams. Because of acid mine drainage or infertile geologies + acid precipitation. Where this is the case, even large (70 feet wide) and warm (80F in summer) streams can hold only brookies, no browns. Brookies are more tolerant of low pH conditions than brown trout.

In the more fertile freestone drainages, the brown trout are present high up into smallish streams. But in the very upper end, where the streams are quite small, it's often entirely brook trout.

The reasons are that very high up in freestone drainages, the pH is usually lower. And the very small streams often have shallow habitat, which favors brook trout not browns. And the very small freestone streams are vulnerable to severe droughts, which can dry up long stretches of the streams, with only a few scattered shallow pools.

A fisheries biologist said their surveys show that during severe droughts the brook trout survive better than browns.

Also, high up tbe water temps are cold, because that's where the water is coming out of the ground. In some parts of northern PA groundwater is 48F. Cold water favors brookies over browns for reproduction.

Regarding barriers. Where natural falls occur, that can be a barrier to passage. But in many cases people have stocked trout above falls. In PA you can generally assume that everything has been stocked.

Falls often occur at a geology bedrock boundary, where the stream is flowing first over a hard (infertile) rock, then flows onto a softer (more fertile) rock layer. The stream carves down into the soft layer, which is what creates the vertical drop.

Often the brown trout/ not brown trout division occurs where the bedrock changes, which changes the water chemistry from less fertile, lower pH upstream, to more fertile, higher pH downstream.

So, sometimes you will find brown trout below falls, but no brown trout above the falls. It might appear that it's because of the physical barrier, but in many cases that may be a water pH thing.

In infertile drainages, falls are often the dividing line between brook trout below the falls and no fish of any kind above the falls. For the same reason. Above the falls the pH is so low that no fish can survive there. But below the falls the water is flowing over a more fertile rock layer and receiving groundwater from the lower rock layer.
Oh yes I see lot of the same predictable trends you you mentioned. I was talking about ones that researchers can’t figure out that should be amenable to brown trout invasion based on what we already know but for some reason are bullet proof. I don’t know where this stream or handful of streams are. Understandably they do not disclose the location but it doesn’t exhibit the same predictable indicators/variables you mentioned above from what I understand.
 
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troutbert

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Marschall and Crowder (1996) used population models to demonstrate that even under strong harvest-induced mortality of larger fish, brook trout populations were unlikely to be extirpated from a particular stream.
"Unlikely to be extirpated" is good news, sort of.

But I hope that peoples' goals will be a little higher than that.
 
Fish Sticks

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"Unlikely to be extirpated" is good news, sort of.

But I hope that peoples' goals will be a little higher than that.
Apparently not in PA.

8-9 million stocked trout plus what ever 600+ private registered with USDA hatcheries can throw at them( some with 5 locations each counting as one registration). Our best watersheds,that other states would already be managing at watershed/sub watershed scale without stocked fish or allowed harvest, get tens of thousands of stocked invasive species each season in most cases.

My question is how are they still here at all?

My optimism about what we can do for brook trout comes from that we have not even tried managing for native brook trout yet. We are doing the exact opposite in this state right now unfortunately in the watersheds we could be reserving for brook trout. PA fish and boat’s Trout management plan talks about trying to restore our way out of trouble but like the BM Huntsman et Al 2022 study i explained in the podcast showed, this will actually likely not benefit brook trout significantly in sympatric watersheds and could actually harm them big time in alot of places if the commission is just building what will become brown trout hotels and ignoring the biotic interactions as usual.
 
silverfox

silverfox

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Are there particular PA streams you have in mind?

In PA the reasons are usually pretty apparent. The streams that hold only brook trout, no browns, are usually infertile, low pH streams. Because of acid mine drainage or infertile geologies + acid precipitation. Where this is the case, even large (70 feet wide) and warm (80F in summer) streams can hold only brookies, no browns. Brookies are more tolerant of low pH conditions than brown trout.

In the more fertile freestone drainages, the brown trout are present high up into smallish streams. But in the very upper end, where the streams are quite small, it's often entirely brook trout.

The reasons are that very high up in freestone drainages, the pH is usually lower. And the very small streams often have shallow habitat, which favors brook trout not browns. And the very small freestone streams are vulnerable to severe droughts, which can dry up long stretches of the streams, with only a few scattered shallow pools. A PA fisheries biologist said their surveys show that the brook trout survive severe droughts better than browns.

Also, high up tbe water temps are cold, because that's where the water is coming out of the ground. In some parts of northern PA groundwater is 48F. Cold water favors brookies over browns for reproduction.

Regarding barriers. Where natural falls occur, that can be a barrier to passage. But in many cases people have stocked trout above falls. In PA you can generally assume that everything has been stocked.

Falls often occur at a geology bedrock boundary, where the stream is flowing first over a hard (infertile) rock, then flows onto a softer (more fertile) rock layer. The stream carves down into the soft layer, which is what creates the vertical drop.

Often the brown trout/ not brown trout division occurs where the bedrock changes, which changes the water chemistry from less fertile, lower pH upstream, to more fertile, higher pH downstream.

So, sometimes you will find brown trout below falls, but no brown trout above the falls. It might appear that it's because of the physical barrier, but in many cases that may be a water pH thing.

In infertile drainages, falls are often the dividing line between brook trout below the falls and no fish of any kind above the falls. For the same reason. Above the falls the pH is so low that no fish can survive there. But below the falls the water is flowing over a more fertile rock layer and receiving groundwater from the lower rock layer.
Tom Clark mentioned one in central PA where they can't find what's prohibiting BT from entering the stream. He said everytime they survey that stream they expect to find that the BT have moved in, but to date they haven't. From a chemistry and thermal standpoint, there's nothing unique about this stream. Everything indicates that the BT should move up into it, but they aren't. BT kryptonite apparently.

My concern is how everything you mentioned plays out in the face of climate change. That all may be the case right now and historically, but what happens w/ a 2-degree average annual temperature increase?

Then at finer scales, what happens where we're liming streams? One liming project that was approved and awaiting final design as far as I'm aware will increase pH on a naturally acidic ST stream w/ wild BT below (also a slated perched culvert removal that acts as a species barrier). If pH functions as a natural barrier (I know it does), are we removing barriers? i.e. Tom Clark's video that fish sticks posted about AMD remediation. What about dropping LWD or rootballs (creating more deep/pool habitat) and narrowing stream channels? How does habitat alteration factor in?

There are some conflicting approaches here if brook trout are the true goal.
 
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weedy

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Tom Clark mentioned one in central PA where they can't find what's prohibiting BT from entering the stream. He said everytime they survey that stream they expect to find that the BT have moved in, but to date they haven't. From a chemistry and thermal standpoint, there's nothing unique about this stream. Everything indicates that the BT should move up into it, but they aren't. BT kryptonite apparently.

My concern is how everything you mentioned plays out in the face of climate change. That all may be the case right now and historically, but what happens w/ a 2-degree average annual temperature increase?

Then at finer scales, what happens where we're liming streams? One liming project that was approved and awaiting final design as far as I'm aware will increase pH on a naturally acidic ST stream w/ wild BT below (also a slated perched culvert removal that acts as a species barrier). If pH functions as a natural barrier (I know it does), are we removing barriers? i.e. Tom Clark's video that fish sticks posted about AMD remediation. What about dropping LWD or rootballs (creating more deep/pool habitat) and narrowing stream channels? How does habitat alteration factor in?

There are some conflicting approaches here if brook trout are the true goal.
A beginner trout fisherman, I just caught my first few wild brook trout last week up at Mill Run near Rexford, looking forward to more and I hope the streams survive.

You wrote:
"what happens w/ a 2-degree average annual temperature increase?"

The global rate of temperature increase since 1979 is estimated to be .13C per decade (which is about .25F per decade), so it would take 80 years for a 2 degree increase. The rate of temperature change is also not accelerating (it has actually slightly diminished since 2015). Local temperature changes may be more or less than this, due to UHI (Urban Heat Island) effects and some known oscillations, such as the AMO and also other unknown factors.
 
silverfox

silverfox

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A beginner trout fisherman, I just caught my first few wild brook trout last week up at Mill Run near Rexford, looking forward to more and I hope the streams survive.

You wrote:
"what happens w/ a 2-degree average annual temperature increase?"

The global rate of temperature increase since 1979 is estimated to be .13C per decade (which is about .25F per decade), so it would take 80 years for a 2 degree increase. The rate of temperature change is also not accelerating (it has actually slightly diminished since 2015). Local temperature changes may be more or less than this, due to UHI (Urban Heat Island) effects and some known oscillations, such as the AMO and also other unknown factors.
Right, though the rate doubled against earlier records. Regardless, the point is that we should (in my opinion) prepare for the worst, and consider accelerated warming as a potential variable to hedge against. Plus, improving thermal conditions should be a goal regardless.

btw, congrats on your first few wild brook trout! I take for granted sometimes that there are a lot of people in the country (or world) who have never seen a wild native brook trout in their native range.
 
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