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Old 10-30-17, 10:23 AM   #11
txc35
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Old 10-30-17, 11:41 AM   #12
Philhutch80
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I would like to thank @jgraham140 and @Splatek16 and @BigT for getting this thread righted once again. @jgraham, you are correct, it is Gillaroo. In the heat of typing I mispelled the word.
@splatek16 you mentioned noticing that trout in various parts of the river look different. I have noticed that as well, even in several other river systems out in Montana and Wyoming. I noticed that the fish closer to the dam would often be more silvery in appearance and have larger black spots with little to no red spots. Have you noticed anything similar?
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Old 10-30-17, 10:43 PM   #13
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Quote:
Originally Posted by Philhutch80 View Post
I would like to thank @jgraham140 and @Splatek16 and @BigT for getting this thread righted once again. @jgraham, you are correct, it is Gillaroo. In the heat of typing I mispelled the word.
@splatek16 you mentioned noticing that trout in various parts of the river look different. I have noticed that as well, even in several other river systems out in Montana and Wyoming. I noticed that the fish closer to the dam would often be more silvery in appearance and have larger black spots with little to no red spots. Have you noticed anything similar?
There are lots of interesting things about the brown trout in the tailwater. They really do resemble Irish Gillaroo from Lough Melvin. Are they descended from Gillaroo or have they converged on a similar phenotype? A genetic analysis would clear that up.

Phenotypic variation is universal. Quantitative geneticists partition total phenotypic variation of, say, color pattern into several components. There is a genetic component that can be further subdivided into an additive genetic component, a dominance component, and epistasis (gene-gene interaction). Geneticists are usually interested in the additive component because it is the only one of the three that can be inherited. The second component of phenotypic variation is the environmental component. For example, if diet or temperature influence the color pattern, that would be an environmental effect.

Genes vs environment is sometimes referred to as nature vs nurture in humans, but the principles are the same.

And then there is an additional component that represents random developmental variation. For example, if the spotting pattern varies between right and left sides of a fish, that would be due to random developmental noise.

To get at the heritability of color pattern, one would have to do experiments with parents and offspring. If the offspring resemble their parents, the heritability of the trait is probably high. Heritability is usually defined as the ratio of the additive genetic component divided by the total phenotypic variation.

I have wondered about the gizzard-like stomach in the Gillaroo. How heritable is that trait? Does a Gillaroo require a diet of snails to express the gizzard-like stomach? If it does, then the heritability might be low. There might also be a gene-environment interaction if only the Gillaroo develop a gizzard-like stomach after eating a diet high in snails.

Finally, how much does diet influence coloration. I can't tell if any of these studies have been done. They may have been, I just haven't had time to find them on Google Scholar.

Confession: my background is in population genetics, ecological genetics, and evolutionary biology. My main research interests are random developmental noise and hybrid zones (in fish, birds, and sagebrush). I was trained with fish, but have found it easier to work with other species.

John
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Old 10-30-17, 11:02 PM   #14
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I do believe that the hooch browns are from a very beautiful strain. (not sure what it is)

Sometimes when there has been a lack of generation and the mouth of the creek below the dam has become very sandy, the browns have taken on a very sandy or pale coloring.

I believe that the river bottom color, water clarity, time of year, diet all contribute to there fantastic coloration.

Wish that there could be a slot or size limit!

Or maybe all browns should be released!!
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Old 10-31-17, 10:37 PM   #15
Mr Brown
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Wow. Just dialing back in with excitement to learn something new from my post and an active and credible resource. To those of you that added knowledge to my day I thank you as I will be reading up on Irish Gillaroo with enthusiasm. To a few of those others, not real sure the fishing community is your cup of tea. But we all know folks like that. right.

PS - stockers go home to my dog. Browns get released with reverence.


Many Thanks,

M
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Old 11-01-17, 08:31 PM   #16
Philhutch80
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Quote:
Originally Posted by jgraham140 View Post
There are lots of interesting things about the brown trout in the tailwater. They really do resemble Irish Gillaroo from Lough Melvin. Are they descended from Gillaroo or have they converged on a similar phenotype? A genetic analysis would clear that up.

Phenotypic variation is universal. Quantitative geneticists partition total phenotypic variation of, say, color pattern into several components. There is a genetic component that can be further subdivided into an additive genetic component, a dominance component, and epistasis (gene-gene interaction). Geneticists are usually interested in the additive component because it is the only one of the three that can be inherited. The second component of phenotypic variation is the environmental component. For example, if diet or temperature influence the color pattern, that would be an environmental effect.

Genes vs environment is sometimes referred to as nature vs nurture in humans, but the principles are the same.

And then there is an additional component that represents random developmental variation. For example, if the spotting pattern varies between right and left sides of a fish, that would be due to random developmental noise.

To get at the heritability of color pattern, one would have to do experiments with parents and offspring. If the offspring resemble their parents, the heritability of the trait is probably high. Heritability is usually defined as the ratio of the additive genetic component divided by the total phenotypic variation.

I have wondered about the gizzard-like stomach in the Gillaroo. How heritable is that trait? Does a Gillaroo require a diet of snails to express the gizzard-like stomach? If it does, then the heritability might be low. There might also be a gene-environment interaction if only the Gillaroo develop a gizzard-like stomach after eating a diet high in snails.

Finally, how much does diet influence coloration. I can't tell if any of these studies have been done. They may have been, I just haven't had time to find them on Google Scholar.

Confession: my background is in population genetics, ecological genetics, and evolutionary biology. My main research interests are random developmental noise and hybrid zones (in fish, birds, and sagebrush). I was trained with fish, but have found it easier to work with other species.

John
Found a really interesting link that goes even deeper in depth regarding the variety of brown trout found in Ireland. It even mentions that genetic variance is so high amongst brown trout that a geneticist thought that all the trout in Ireland have 5x as much genetic diversity as humans do. Good read and some unreal photos! http://www.angling-ireland.com/brown_trout
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Old 11-04-17, 12:44 PM   #17
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Quote:
Originally Posted by Philhutch80 View Post
Found a really interesting link that goes even deeper in depth regarding the variety of brown trout found in Ireland. It even mentions that genetic variance is so high amongst brown trout that a geneticist thought that all the trout in Ireland have 5x as much genetic diversity as humans do. Good read and some unreal photos! http://www.angling-ireland.com/brown_trout
Nice article. Thanks.

It isn't unusual that trout have more genetic variation than humans. First, they are partial polyploids, so they have twice as many chromosomes as diploids. And we have relatively little genetic variation compared with other vertebrates. The presumed cause of low human genetic variation is a genetic bottleneck 70,000 years ago caused by the eruption of the Toba super-volcano. The Toba Hypothesis, though, is controversial as the cause of the bottleneck. All we know is that the human population decreased to just a few thousand individuals. This is based on sequence patterns in the DNA.

John
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