Interesting Study

[DaveS]

I'd think spawning of either group, wild or hatchery, is dependent on a) water temperature, and b) photoperiod or length of daylight. So how do those two variables compare with each group? And then how does it compare to other hatchery strains? It is interesting stuff!

 

[pcray1231]

Dave,

I'm talking out my rear end here, I'm not a fisheries biologist. Just guessing based on a more broad scientific background and a decent understanding of evolution.

But if I had to guess, I would say that your a and b are the primary forces pulling the trigger. But that genetics is what determines the trigger weight.

i.e. if a strain of stockies were bred to, say, breed earlier in the fall, then through selective breeding processes biologists have installed a "hair trigger". They're still responding to photoperiod just like the wild fish, but it happens more quickly.

But "hatchery fish" shouldn't be looked at as a single strain anymore than wild fish should be. There are multiple strains of both. For instance, Virginia's hatchery fish may be very different than the PFBC's strain, which can be different yet from the strains raised in private PA hatcheries.

 

[DaveS]

Yea, that's sort of what I meant. How does the hatchery strain from VA "triggering point" compare with that of other state's strain. And then, in turn how those relate to the various wild fish they could impact.

 

[geebee]

I think trout are different to char - brown trout will spawn with Atlantic Salmon and hence the worries in Europe about stockies degrading wild runs; and bows spawn with cutts as we know.

Char are a bit different due to genetics or environment. I don't think brookies and lakers/togue interbreed much either.

In the Cape Cod study, sea run brookies from the Sandwich hatchery had 0% genetic effect on the wild stocks in the quashnet and child's rivers, that's why they stopped stocking over the wild fish.

 

[SBecker]

Talked to Robert and he told me when he has a chance he will chime in.

 

[Rowbear]

Hey all,

Shane, thanks for the invitation to view this thread and jump in. It's interesting to see this getting discussed in an angling forum! I don't have much time to respond to everything posted in response, but I thought I'd add a few quick bits:

1) The evidence for interbreeding between hatchery and wild BKT is mixed, in fact it is VERY mixed. Some disagreement between studies may be due to differences in methods. We feel very confident that our results are solid, ie. the methodology was sound. I am also equally confident that these results don't apply everywhere, but rather describe what happened in this particular situation. The point we thought was important was to underscore that it does vary, and its important to evaluate the integrity of wild stocks and not write them off as 'compromised' even if they have a long history of being stocked upon.

2) In terms of how this lack of interbreeding happened, there are lots of possibilities. All of the ones suggested here are possible and valid. There was another study that showed even different strains of wild BKT don't always interbreed as much as you would expect when they throw them in the mix together. This is something I would love to study more and is a very interesting ecological question.

3) The longevity of the hatchery strain in the system is a real interesting question. If stocking is stopped, it could be that the hatchery fish will disappear in a decade or even shorter. That has been the case in some systems, but not in others. This most certainly depends on the strain itself and its vigor in the wild, and a strain stocked in Virginia may blink out while the same strain stocked in New Hampshire may persist for decades.

I'm sure the lack of conclusive answers is frustrating here, and there is certainly some value to taking a precautionary approach to hatchery supplementation when trying to preserve wild stocks. It has value and it has risk, in my opinion. In the end it comes down to what we value, as one person suggested here. But there are many scientists out there that hold much stronger opinions on this than me, and many of them have been studying this question longer than I have. If you have any specific questions about this study I would be happy to answer them. If you have questions about some of the larger implications of hatchery vs. wild debates, I can offer my opinion on that but can't answer all the questions it raises. It's definitely fun to talk about though and I always like hearing other people's take on it.

Thanks for your interest in this work!

 

[PatrickC]

Thanks you for chiming in. Excellent stuff!

I wonder if Pcray will agree? Hmmm? Sorry, I have to beat up on Pcray because I can't beat up on my engineer wife that seems to think she has to verify any statement I make...even in areas I hold advanced degrees. Goobers ;-)

 

[PatrickC]

And, my wife just looked over my shoulder, read this....and LAUGHED

 

[pcray1231]

haha.

FWIW, no, I don't disagree with anything rowbear said.

Not that this is a surprise. Unlike many, I actually read the study, and it's conclusions, and understand how to interpret scientific results. . Zing!

The one thing I learned was this:

The evidence for interbreeding between hatchery and wild BKT is mixed, in fact it is VERY mixed.

Everything I've seen has been with similar conclusions as this study has been, so not all that mixed. That said, it's not my job to study this, but rather a side interest. Thus, I haven't done an exhaustive literature search like he probably has. Instead, I've only read those studies that searched me out! And when you troll predictable, repeatable circles, you tend to only see studies that support their position, and you only get one side of the story.

It's nice to get someone commenting who has actually studied this, officially, and has done their due diligence.

Thanks rowbear! And lack of conclusive answers is what biology is all about, lol. (As a "hard sciences" guy, I have to zing the bio guys). Too many dependent variables. Leaves you with the choice of not sufficiently isolating them, or narrowing the study so much that it only tells you .00001% of the story. I prefer the latter, which this study fits, but it results in needing a whole lot of studies just like before a clearer picture emerges.

 

[PatrickC]

pcray1231 wrote:
And lack of conclusive answers is what biology is all about, lol. (As a "hard sciences" guy, I have to zing the bio guys). Too many dependent variables. Leaves you with the choice of not sufficiently isolating them, or narrowing the study so much that it only tells you .00001% of the story. I prefer the latter, which this study fits, but it results in needing a whole lot of studies just like before a clearer picture emerges.

My bride struggles with this as well. What I have always found interesting about biology is that it is the combination of all of those hard sciences. And yet, when you put them all together, variation becomes terrible unpredictable. I have always said that all of biology does fit into predictable algorithms, but we just have not had enough time to observe all of the scenarios it would take to write them. And, because of biology's inherent nature of adaptation, we probably will never be able to make all of the necessary observations to apply algorithms to all of life. The good news, as the philosophy of science teaches us, we do continually take steps towards truth, we're just never going to attain it fully.

Some of us need very predictable models to get through our days and some of us can roll with it. That's the difference between an engineer/chemist/physicist/mathematician and someone who works in the arena of life sciences. The best news, it takes all of us to make it work!

 

[Chaz]

csoult wrote:
Is it possible that there is no interbreeding due to different reproductive cycles? This would make the most sense to me. Even if they were just off by a few weeks would make all the difference. I'm not sure what triggers the spawn but maybe it is much less environmental than some think.

Also, this brings up another question..... How does this change your view of tigers. If this study is true than wouldn't that also be the case with natives breeding with browns. Or maybe true natives do not breed with browns but only brook trout that were stocked generations ago.

Your first question is most likely the reason, that and the fact that they probably don't use the same stream sections.
Tiger trout are a whole other matter, they are 2 different genus' trying to spawn and the brookie has to have defective genes to make the spawning successful. So no it doesn't change my view of how tigers occur in the wild. It is pretty rare.