Challenge to all Trout Camps

[pcray1231]

Interesting on Jeans. I buy the acidification argument. The numbers shown do not reflect my experiences on size at all, they run pretty big, and I catch plenty in the 7-10" range on every trip, and there have been a couple in the 10-12 range too. I suspect they do the shocking either near the mouth or up on top rather than in the heart of it. And yeah, they run smaller in those areas. No mention of browns either, though they are present.

Silver, yes, the number of trout 7" or longer has always been a very poor metric, IMO. Very arbitrary, when the PFBC already admits harvest is nil, 7" fails to carry any significance whatsoever from a conservation standpoint. Just my opinion. I like to catch bigger fish for any population, but it's relative to the population. There are streams where 2 and 3 inchers are the normal and you consider a 5" as a "nice fish", and a 7 incher is a monster. And that's fine. And there are tons of streams where 5-8 inchers are normal, 8-10 is a "nice fish" with a 10-12 being a hoss fish. A lot of brown trout streams where 10-12 is normal, mid teens is a "nice fish", and anything 17 or above is a hoss. And then you go all the way to steelhead, where anything under 20 is "just a jack", 24" is an average fish, and 30 is where monster territory begins.

And as in Jeans, a lot of these streams the size varies, often inversely with the population. They don't become more or less valuable when a population falls and size gets better, nor do they become better or worse if the population spikes and size goes down. That's just the nature of that stream.

 

[silverfox]

Interesting on Jeans. I buy the acidification argument. The numbers shown do not reflect my experiences on size at all, they run pretty big, and I catch plenty in the 7-10" range on every trip, and there have been a couple in the 10-12 range too. I suspect they do the shocking either near the mouth or up on top rather than in the heart of it. And yeah, they run smaller in those areas. No mention of browns either, though they are present.

Silver, yes, the number of trout 7" or longer has always been a very poor metric, IMO. Very arbitrary, when the PFBC already admits harvest is nil, 7" fails to carry any significance whatsoever from a conservation standpoint. Just my opinion. I like to catch bigger fish for any population, but it's relative to the population. There are streams where 2 and 3 inchers are the normal and you consider a 5" as a "nice fish", and a 7 incher is a monster. And that's fine. And there are tons of streams where 5-8 inchers are normal, 8-10 is a "nice fish" with a 10-12 being a hoss fish. A lot of brown trout streams where 10-12 is normal, mid teens is a "nice fish", and anything 17 or above is a hoss. And then you go all the way to steelhead, where anything under 20 is "just a jack", 24" is an average fish, and 30 is where monster territory begins.

And as in Jeans, a lot of these streams the size varies, often inversely with the population. They don't become more or less valuable when a population falls and size gets better, nor do they become better or worse if the population spikes and size goes down. That's just the nature of that stream.

Exactly. Whether it's estimated biomass or average fish size, that any stream or stream section is assigned a higher or lower "value" based on human-imposed metrics seems wrongheaded to me.

 

[FarmerDave]

Not implying anyone here is not intelligent just saying no one here is really professionally qualified to evaluate these studies or make their own independent assessment. Thats why I talk to the authors or the authors peers to get context before I do science communication with whats published in most cases, i am not qualified to evaluate these things wither. I have nothing original to share its all people smarter than me i am just a vehicle for their findings to hopefully reach more of the public. I don’t create any of it and its not my idea.

Yes you are, and you are doing it again. But I will give you the benefit of doubt that it is unintentional.

There are several regulars on here that are engineers or scientists and a few others that visit from time to time. And just so you know, I am not really a farmer.

I have no doubt that you are a smart guy, but when people say things like that, I raise my eyebrows.

Is there a test to decide who is really professionally qualified to evaluate studies or "make their own independent assessment." We all have every right to agree or disagree.

 

[silverfox]

To clarify, I'm not implying that PFBC's management ends at stream section classification. I know they're improving their approach all the time. I also know they do take watershed-level dynamics into account for project prioritization. Dave Nihart touches on that in the presentation below, and I'm ecstatic to hear that they're prioritizing projects based on a watershed overview. I think TU's prioritization tool is one of the coolest things since sliced bread.

I just wish they could focus on these things more. Which requires money. Which is limited by the cost of the stocking program=my disdain for the current level of stocking in PA. I could be convinced that stocking generates money = more conservation, but the cost of stocking (rearing + distribution) keeps going up, which seems to imply less money for conservation rather than more.

I think this is where federal and state funding for conservation is so important, but I wish there was more appetite to reduce stocking as a financial tool as well.

 

[Fish Sticks]

Yes you are, and you are doing it again. But I will give you the benefit of doubt that it is unintentional.

There are several regulars on here that are engineers or scientists and a few others that visit from time to time. And just so you know, I am not really a farmer.

I have no doubt that you are a smart guy, but when people say things like that, I raise my eyebrows.

Is there a test to decide who is really professionally qualified to evaluate studies or "make their own independent assessment." We all have every right to agree or disagree.

I will point out that I included myself as part of the group not qualified to discredit peer reviewed fisheries science so if your assertion that I am implying people are unintelligent simply by being unqualified was in fact true this would mean I would have included myself in that group.

There may be a nuclear physicist in here but that doesn’t qualify anyone to interpret fisheries science. I am not going to mention my profession on here and I never do because it’s irrelevant.

I would say if you did 4 years of undergrad in biology and 4 to 7 years in a PhD program with a focus on brook trout ecology, conservation genetics, or invasion biology your qualified to make an independent assessment that discredits someones of equal level of education/training (if you have supporting evidence) and if you choose to share that assessment with the public you can responsibly do so. Anyone can make their own “independent assessment” they just should not advertise it to the public if their not qualified to do so. This is why we call it “peer reviewed science” because a peer of equal education and training, often multiple, evaluate it. So for instance the study I posted was evaluated by brook trout ecologists throughout the native range and felt to be of high enough quality and relevance to post on the EBTJV public science com page. Does anyone here seriously think their more qualified? No but that has nothing to do with intelligence.

Doctors don’t work on the hadron collider and quantum physicists don’t place intracardiac drug elluting stents. Neither is unintelligent. My statement was not meant to call anyone unintelligent (it included myself).

 

[vcregular]

Jeans Run - 2006 - that was the flood of all floods. June. May have impacted in the short term.

 

[Fish Sticks]

Yes you are, and you are doing it again. But I will give you the benefit of doubt that it is unintentional.

There are several regulars on here that are engineers or scientists and a few others that visit from time to time. And just so you know, I am not really a farmer.

I have no doubt that you are a smart guy, but when people say things like that, I raise my eyebrows.

Is there a test to decide who is really professionally qualified to evaluate studies or "make their own independent assessment." We all have every right to agree or disagree.

Even if I am intelligent or not is irrelevant. If I just post articles taken off vetted scientific communication websites as seems to be made light of all the time, i could have the iq of a toaster oven. It doesn’t matter because the concepts and findings are not my own.

 

[Mike]

I will point out that I included myself as part of the group not qualified to discredit peer reviewed fisheries science so if your assertion that I am implying people are unintelligent simply by being unqualified was in fact true this would mean I would have included myself in that group.

There may be a nuclear physicist in here but that doesn’t qualify anyone to interpret fisheries science. I am not going to mention my profession on here and I never do because it’s irrelevant.

I would say if you did 4 years of undergrad in biology and 4 to 7 years in a PhD program with a focus on brook trout ecology, conservation genetics, or invasion biology your qualified to make an independent assessment that discredits someones of equal level of education/training (if you have supporting evidence) and if you choose to share that assessment with the public you can responsibly do so. Anyone can make their own “independent assessment” they just should not advertise it to the public if their not qualified to do so. This is why we call it “peer reviewed science” because a peer of equal education and training, often multiple, evaluate it. So for instance the study I posted was evaluated by brook trout ecologists throughout the native range and felt to be of high enough quality and relevance to post on the EBTJV public science com page. Does anyone here seriously think their more qualified? No but that has nothing to do with intelligence.

Doctors don’t work on the hadron collider and quantum physicists don’t place intracardiac drug elluting stents. Neither is unintelligent. My statement was not meant to call anyone unintelligent (it included myself).

I disagree in part. Depending upon course selection and foci of professors teaching the courses, fisheries, wildlife, and ecology undergrads taking graduate courses and MS candidates as part of their graduate level training regularly take courses and do thesis work that involve or require critique of the scientific literature, that is, they are taught to critique peer reviewed papers. For example, a biometry course ( biological statistics) may include frequent critique of the materials and methods portions of scientific papers, ie, the designs of the studies. Critical thinking and learning how to conduct research are usually important aspects of MS educations in these fields.

 

[FarmerDave]

I will point out that I included myself as part of the group not qualified to discredit peer reviewed fisheries science so if your assertion that I am implying people are unintelligent simply by being unqualified was in fact true this would mean I would have included myself in that group.

There may be a nuclear physicist in here but that doesn’t qualify anyone to interpret fisheries science. I am not going to mention my profession on here and I never do because it’s irrelevant.

I would say if you did 4 years of undergrad in biology and 4 to 7 years in a PhD program with a focus on brook trout ecology, conservation genetics, or invasion biology your qualified to make an independent assessment that discredits someones of equal level of education/training (if you have supporting evidence) and if you choose to share that assessment with the public you can responsibly do so. Anyone can make their own “independent assessment” they just should not advertise it to the public if their not qualified to do so. This is why we call it “peer reviewed science” because a peer of equal education and training, often multiple, evaluate it. So for instance the study I posted was evaluated by brook trout ecologists throughout the native range and felt to be of high enough quality and relevance to post on the EBTJV public science com page. Does anyone here seriously think their more qualified? No but that has nothing to do with intelligence.

Doctors don’t work on the hadron collider and quantum physicists don’t place intracardiac drug elluting stents. Neither is unintelligent. My statement was not meant to call anyone unintelligent (it included myself).

In other words, I was right. It wasn't intentional.

As far as this latest argument, I am not going to stop reading studies and coming to my own conclusions just because you say I am not qualified to do so. Afterall, they are my own.

Healthy discussion and disagreement is the foundation of science. I have not read all the responses. In fact, I haven't read most of them. So I have no idea where this train of thought is coming from, nor do I care.
I didn't see where anyone was making light.

I have been a fan of protecting Brook trout long before you found this site, and 99 time out of 100, we likely agree. I was only commenting on the condescending tone that I sensed. If I am the only one who sensed that, then I apologize.

Good day, sir.

P.S. I liked the toaster oven comment.

 

[Fish Sticks]

In other words, I was right. It wasn't intentional.

As far as this latest argument, I am not going to stop reading studies and coming to my own conclusions just because you say I am not qualified to do so. Afterall, they are my own.

Healthy discussion and disagreement is the foundation of science. I have not read all the responses. In fact, I haven't read most of them. So I have no idea where this train of thought is coming from, nor do I care.
I didn't see where anyone was making light.

I have been a fan of protecting Brook trout long before you found this site, and 99 time out of 100, we likely agree. I was only commenting on the condescending tone that I sensed. If I am the only one who sensed that, then I apologize.

Good day, sir.

P.S. I liked the toaster oven comment.

I agree that I would not dissuade anyone from reading the studies and coming up with their own questions and observations especially because you can take your impression and e-mail the authors or peers familiar and get their take expertise and context. You may find out in case’s conclusions you have made are very valid and in others that an unknown or little mentioned/highlighted relationship or concept resulted in the conclusion of the study. These fisheries scientists love to talk about their work with people despite being super super busy and i think thats the best form of science communication. I wish there was more funding for direct science communication from the subject matter experts but grants mostly just fund publications so its hard. Alot of them are very passionate and do to a degree on their own time in some cases.

 

[Fish Sticks]

I disagree in part. Depending upon course selection and foci of professors teaching the courses, fisheries, wildlife, and ecology undergrads taking graduate courses and MS candidates as part of their graduate level training regularly take courses and do thesis work that involve or require critique of the scientific literature, that is, they are taught to critique peer reviewed papers. For example, a biometry course ( biological statistics) may include frequent critique of the materials and methods portions of scientific papers, ie, the designs of the studies. Critical thinking and learning how to conduct research are usually important aspects of MS educations in these fields.

Sure the person you described would still be a fisheries scientist. The example I gave was more to demonstrate a common rigorous educational process of fisheries subject matter experts but as you mentioned if you did 4 years of bio/ecology got one or two MS degrees that concentrated on statistical analysis, study design, and working with the fish of study requiring you to read all the relevant existing literature this would be another valid pathway to becoming a native brook trout subject matter expert as mentioned by you.

 

[pcray1231]

In general, scientists are trained to read papers. That's true whether they are fisheries scientists, engineers, physicists, chemists, etc. Look at data. Look at conclusions. And if they are knowledgable of the subject matter at hand, ask themselves whether they would make the same conclusion from the same data.

In most cases they will agree with most, not all, and still be happy as a peach that the study was conducted, take the data collected, and use that data to further their own knowledge.

The study in question was regarding the efficiency of barriers. The authors noted that streams with barriers were more likely to be brookie streams. Correlation, not causation. They only published the raw data as graphs, but digging into it, about half of the "brookie streams" had barriers. And half didn't. All of them had other characteristics in common, namely higher gradient and smaller. Of streams that other factors say should have brown trout present, none of them had barriers.

The clear conclusion isn't that barriers help a stream be brookies, or that they don't. It's that the data was inconclusive on the topic. The species present in every stream studied was fully explainable and predictable based on stream size and gradient alone. Therefore, no conclusion can be drawn on the topic. In all cases that barriers were present, you were going to have brook trout with or without the barrier. In no cases where a barrier was present would you expect, based on other factors, to find brown trout, and they didn't.

I still think barriers may be effective in some circumstances. The test would be in a stream, that by all other factors, should be a brown trout stream, but has a long standing barrier and browns never had access, and therefore remains all brookies. No such streams were found in the study, but that doesn't mean they don't exist.

My wow moment was on those other things. Stream size, gradient, and alkalinity was tested. Those things are usually well correlated, but I always kind of viewed alkalinity as perhaps the meaningful one. I openly worried that as we clean up acid from mines and acid rain, good things for sure, but that it would cause many brookie streams to flip over to brown trout and be harmful to brookie populations. But from the data, a full half of the brookie streams had no barriers AND excellent alkalinity. Browns had access, and no apparant chemistry disadvantages, and brookies won there anyway based on size and/or gradient. That's an encouraging thought for the brookie streams in the rest of our state.

 

[Fish Sticks]

In general, scientists are trained to read papers. That's true whether they are fisheries scientists, engineers, physicists, chemists, etc. Look at data. Look at conclusions. And if they are knowledgable of the subject matter at hand, ask themselves whether they would make the same conclusion from the same data.

In most cases they will agree with most, not all, and still be happy as a peach that the study was conducted, take the data collected, and use that data to further their own knowledge.

The study in question was regarding the efficiency of barriers. The authors noted that streams with barriers were more likely to be brookie streams. Correlation, not causation. They only published the raw data as graphs, but digging into it, about half of the "brookie streams" had barriers. And half didn't. All of them had other characteristics in common, namely higher gradient and smaller. Of streams that other factors say should have brown trout present, none of them had barriers.

The clear conclusion isn't that barriers help a stream be brookies, or that they don't. It's that the data was inconclusive on the topic. The species present in every stream studied was fully explainable and predictable based on stream size and gradient alone. Therefore, no conclusion can be drawn on the topic. In all cases that barriers were present, you were going to have brook trout with or without the barrier. In no cases where a barrier was present would you expect, based on other factors, to find brown trout, and they didn't.

I still think barriers may be effective in some circumstances. The test would be in a stream, that by all other factors, should be a brown trout stream, but has a long standing barrier and browns never had access, and therefore remains all brookies. No such streams were found in the study, but that doesn't mean they don't exist.

My wow moment was on those other things. Stream size, gradient, and alkalinity was tested. Those things are usually well correlated, but I always kind of viewed alkalinity as perhaps the meaningful one. I openly worried that as we clean up acid from mines and acid rain, good things for sure, but that it would cause many brookie streams to flip over to brown trout and be harmful to brookie populations. But from the data, a full half of the brookie streams had no barriers AND excellent alkalinity. Browns had access, and no apparant chemistry disadvantages, and brookies won there anyway based on size and/or gradient. That's an encouraging thought for the brookie streams in the rest of our state.

I see the table your looking at its the one with 8 landscape characteristics including alkalinity, stream size, elevation, gradient and others. You are arriving at the conclusion of correlation without causation because your observations are based off what, at that point in the article, is just observational data not yet put into statistical models. Your looking at the observational data before it goes into the statistical models that controls for variables and determines causal relationships. The Author took the data that you mentioned trends in/observations and then after that ran it through PCA, PERMANOVA, ANCOVA and other statistical functions to look for caudal relationships. It would seem like these relationships between gradient and stream size were tested against probability of the primary end point by these statistical models independently of barrier presence. This seems to be the innate purpose of establishing 8 stream characteristics gradients, ruling out correlation without causation. But i could be wrong i am not qualified to be evaluating this stuff because I am not a fisheries scientist so your not getting much worth from me interms of looking at study design/stats. At the end of the day i am just taking science communication approved by EBTJV and sharing its conclusions with you all.

I think the best way to test your stated interpretation is to respectfully ask the author and subject matter expert to comment on how he ruled out correlation without causation. My guess is you will find their experience designing the study, exclusion criteria, possible confounding variables to control and working with the statisticians on what models to use and what the data inputed tells us, is that there is evidence for a causal component to the strongly observed barrier effect.

mkirk@allegheny.edu

 

[silverfox]

In general, scientists are trained to read papers. That's true whether they are fisheries scientists, engineers, physicists, chemists, etc. Look at data. Look at conclusions. And if they are knowledgable of the subject matter at hand, ask themselves whether they would make the same conclusion from the same data.

In most cases they will agree with most, not all, and still be happy as a peach that the study was conducted, take the data collected, and use that data to further their own knowledge.

The study in question was regarding the efficiency of barriers. The authors noted that streams with barriers were more likely to be brookie streams. Correlation, not causation. They only published the raw data as graphs, but digging into it, about half of the "brookie streams" had barriers. And half didn't. All of them had other characteristics in common, namely higher gradient and smaller. Of streams that other factors say should have brown trout present, none of them had barriers.

The clear conclusion isn't that barriers help a stream be brookies, or that they don't. It's that the data was inconclusive on the topic. The species present in every stream studied was fully explainable and predictable based on stream size and gradient alone. Therefore, no conclusion can be drawn on the topic. In all cases that barriers were present, you were going to have brook trout with or without the barrier. In no cases where a barrier was present would you expect, based on other factors, to find brown trout, and they didn't.

I still think barriers may be effective in some circumstances. The test would be in a stream, that by all other factors, should be a brown trout stream, but has a long standing barrier and browns never had access, and therefore remains all brookies. No such streams were found in the study, but that doesn't mean they don't exist.

My wow moment was on those other things. Stream size, gradient, and alkalinity was tested. Those things are usually well correlated, but I always kind of viewed alkalinity as perhaps the meaningful one. I openly worried that as we clean up acid from mines and acid rain, good things for sure, but that it would cause many brookie streams to flip over to brown trout and be harmful to brookie populations. But from the data, a full half of the brookie streams had no barriers AND excellent alkalinity. Browns had access, and no apparant chemistry disadvantages, and brookies won there anyway based on size and/or gradient. That's an encouraging thought for the brookie streams in the rest of our state.

The clear conclusion isn't that barriers help a stream be brookies, or that they don't. It's that the data was inconclusive on the topic. The species present in every stream studied was fully explainable and predictable based on stream size and gradient alone. Therefore, no conclusion can be drawn on the topic. In all cases that barriers were present, you were going to have brook trout with or without the barrier. In no cases where a barrier was present would you expect, based on other factors, to find brown trout, and they didn't.

I can't entirely agree with that assessment. The majority of the paper was less about whether barriers determine the probability of a species being present and more about trade-offs between isolation and invasion. The name of the paper. Even on the issue of barriers and sympatry, this line;

and no sympatric populations had a barrier downstream.

seems immensely important. For me, the issues surrounding natural zonation like gradient and temperature, only serve to reinforce the conclusion (below).

Also, I didn't interpret this to imply that all of the barriers are strictly impenetrable. They mentioned wetlands and beaver dams as types of barriers, which to me, was an important point. I also think they adequately addressed the gradient effect as a natural driver for separation below.

My biggest takeaway from the paper was:

We suggest that isolation management is generally applicable for the conservation of Brook Trout in (1) low-gradient streams(<34 m/km; Figure 4) where strong elevation and temperature gradients that lead to strong zonation patterns are lacking, (2) relatively large (>4km2; Figure 3) headwater streams that Brown Trout can invade when barriers are absent, and (3) at the edges of their distribution, where populations have been greatly reduced (Hudy et al. 2008).

Of importance here is that they're talking about streams that currently do not have sympatric populations, but have conditions that would allow brown trout to move in. For example, a low gradient, medium to large stream with chemical and temperature characteristics that would likely lead to mixed populations without a barrier if brown trout were to be introduced to the system.

I swore I wouldn't wade into this angle of the discussion...

These topics span biology, ecology, natural resource management, public policy, sociology, psychology, statistics, economics, and on and on and on. I don't think there's enough time in one's life to become an expert in all aspects of it.

Silos of information and specialist bias are some of the issues I’ve seen. A biologist might be too focused on the biological angle of the situation without considering or placing enough weight on the social, psychological, or economic aspects, and vice versa.

I’ve said several times that angling regulations psychologically impact the public’s perception of a species’ need for conservation or, at a minimum, that a species needs special attention. A point Dan Goetz echoed almost verbatim in the video I posted. Are Dan and I wrong? Does Dan or my credentials matter regarding the legitimacy of the point we’re arguing? Do I need to have published my essay on the topic and had it reviewed by peers to make that concept true? Do I need to cite a study published by others to prove the concept has value? Which science degree lends the most credibility to that specific argument? A biologist? Ecologist? Public policy analyst? Psychologist?

Can we debate on a public forum about the idea without having to display our certificates in our signature line?

 

[FarmerDave]

Can one of you point me to the study that you are talking about? Feel free to send the post number in a PM.

The previous two posts are making a lot of sense, but before I hand out likes, I'd like to read and evaluate it myself if that is OK.

 

[silverfox]

Can one of you point me to the study that you are talking about? Feel free to send the post number in a PM.

The previous two posts are making a lot of sense, but before I hand out likes, I'd like to read and evaluate it myself if that is OK.

Probably easier to just repost the link than trying to find where it was originally mentioned. Pick me! Pick me!

Evaluating the Trade-Offs between Invasion and Isolation for Native Brook Trout and Nonnative Brown Trout in Pennsylvania Streams — EBTJV

A popular conservation strategy for native trout species in western North America is to prevent invasions by nonnative trout by installing barriers that isolate native trout populations into headwater streams. In eastern North America, native Brook Trout Salvelinus fontinalis are frequently...

easternbrooktrout.org

 

[pcray1231]

The Author took the data that you mentioned trends in/observations and then after that ran it through PCA, PERMANOVA, ANCOVA and other statistical functions to look for caudal relationships.

1. I'm familiar with and run those models on a daily basis. They do not show causal relationships, they show only correlation and the statistical significance of that correlation. No statistical analysis can ever tell you causation, that is not what statistics do. And PCA was used precisely because multiple factors were correlated so well, so it makes sense to group them. For example, in the study area, high gradient streams were all small, farther from the nearest stocking point, etc. It's like us saying in passing, your infertile small high gradient mountain freestoner. It's the ones that don't fit the correlated grouping that are interesting, because they give you insight on which of those factors matter. What about a FERTILE small mountain freestoner?

2. The authors ran those models, and found the correlation strongest with stream size and gradient. They noted that all streams with barriers were high gradient and small. They noted that several factors were all correlated with each other, the highest correlation with species being gradient, and the 2nd highest being stream size. Barriers come along for the ride because no low gradient large streams had barriers. I did not disagree with the authors conclusions in any manner. I added an observation that they did not. They dismiss alkalinity because in their study area, all streams had what I call "good" alkalinity, and thus no correlation was found and it wasn't talked about much. Within the study, that is correct. But me, knowing a larger state, where small, high gradient, with good alkalinity is actually not normal at all, that's kind of unique. I found it very interesting that those streams were still brookies.

Brook Trout streams were smaller in size, higher in elevation, and located farther east, occupied positions closer to the headwater source of the stream, and had higher stream gradients than Brown Trout streams (Figure 2; Table 1). These differences between Brook Trout and Brown Trout streams were predominately associated with the longitudinal stream gradient (i.e., stream size), with Brown Trout replacing Brook Trout along a gradient of increasing stream size (Figure 3). Interestingly, Brown Trout occupied high stream positions only in low-gradient streams (<34 m/km), whereas only Brook Trout occupied high stream positions in high-gradient streams (Figure 4). The second and third axes explained 19.5% and 16.5% of the variance, respectively, and neither axis was associated with differentiation between Brook Trout and Brown Trout streams (PERMANOVA; both P > 0.14).

Summary: Stream size matters. Gradient matters in small streams (brown trout will only be present in small streams if it is also low gradient). None of the other factors (including barriers) can be statistically shown to matter in the study data (that doesn't mean they don't matter, just that the statistics don't bear it out in the study at hand).

Odds ratios indicated that sites were 12 times as likely to have only Brook Trout when a barrier was present (Table 2). There were several notable differences in landscape-level characteristics between Brook Trout streams with and without barriers. Importantly, streams with barriers had smaller areas and steeper gradients than those without barriers (Table 1; Figure 4). In addition, barriers were present in 50% of Brook Trout streams in the 0–4-km2 range and 75% of Brook Trout streams in the 4–8-km2 range but were not present in the largest streams (Figure 3). Importantly, streams with barriers had smaller areas and steeper gradients than those without barriers

The statistics didn't bear out an effect of barriers. Yet, on the face of it, a stream with a barrier is 12x more likely to be brookies. How can this be explained? Good question, so they addressed it above. Barriers were co-correlated with streams size and gradient. Within the limits of this study, streams with barriers would have been expected to be brookies anyway based on other factors, so we weren't able to prove that barriers actually help.

It does not discount that barriers may help. Just like having no effect of alkalinity does not actually prove that alkalinity doesn't matter. The study is limited, it didn't really effectively test those things.

In fact in the discussion, it discusses that they probably are useful and explains in what scenarios they may be useful. Those scenarios were not in the study. i.e. the takeaway is, we set out to prove the effectiveness of barriers. Our study data didn't really prove that. But it didn't disprove it either. We suggest barriers would be useful in these specific situations (isolated populations of brook trout, around the range edges, in lower gradient streams). We didn't have those situations in this study.

And I agree with them completely.

 

[Fish Sticks]

I have a basic understanding of statistics. It looks like what your saying is there was collinearity in the regression model?

It would seem like the fact that zero sympatric streams had a barrier but yet gradient was not drastically different would support a causal link to barriers.

 

[lycoflyfisher]

The beauty of science and peer reviewed research is asking questions and testing others' hypothesis. This is how we learn. The mistake is in accepting all published papers as the gospel truth without critical thinking and analyzation.

 

[Fish Sticks]

The beauty of science and peer reviewed research is asking questions and testing others' hypothesis. This is how we learn. The mistake is in accepting all published papers as the gospel truth without critical thinking and analyzation.

I agree and this obviously was peer reviewed before it made it to our forum. I think “peer” is the operative term and I would be interested hear that review process from the fisheries scientists that added it to the EVTJV science and data page as well in addition to ours.