Creating cold tolerant tropical fish.

[esoxlucius]

What you're suggesting is actually happening now. Just very very very very slowly. That slowly that we'd never see it in a lifetime, hell 20 lifetimes! It's called global climate change and as the climate changes everything on earth has to adapt. So yes, even without your help your warm water whatever fish you want to choose will eventually have to cope with even warmer or for the sake of your experiment, colder water temps sooner or later.

Just slightly off topic, i watched a documentary once about global warming and humans have very very little to do with it. It's the position of the earth/sun/solar system as they all spin through the galaxy that effects the conditions on our planet. I am sat writing this in the comfort of my front room in the uk, nice and warm. Just 10000 years ago i would have been under 2 miles of ice. Humans have had nothing to do with why that ice is no longer here, and humans will have nothing to do with the process that will, in time, bring it back.

 

[Drstrangelove]

Hypothetically, if you took a few dozen tropical fish (maybe one that is already semi-cold tolerant, such a blue tilapia) and chilled the water down to the point where they start going unconscious or dying. You let all but a few die, and then remove the few survivors, and breed them. If you continue this process over many generations, could you in theory, breed a cold tolerant cichlid? This is a completely hypothetical experiment, I was just wondering if it was possible, and if so, why hasn't it been done?

Real mutation is random. It takes far more than a few fish being bred before you will see it, and most mutation is neutral, while some is unfavorable. The genes don't decide to get better because something bad happened: in extraordinarily rare circumstances they simply change and the effect might be good, bad or nothing.

People have been around malaria for 4,000 years (200 generations) and smallpox for 10,000 years (500 generations.) We still die from it. A lot. There was a mutation (sickle cell) that happened for malaria, but there's no mutation that saves us from smallpox. And people die from sickle cell.

Grizly bears evolved into polar bears at least 70,000 but perhaps as much as 1.5 millions years ago. That's at least 14,000 generations.

It's not like you are simply selecting for a particular feature (like we do horses, dogs, etc.) Breeding to get an inconsequential change like hair color or size of an animal is nothing like changing it's reproductive, circulatory, respiratory, and digestive systems which are all severely affected by temperature.

Yes, some abilities might have been retained if it was recently a cold water fish (it might have adaptive respiratory or digestive features for example) but to take a true tropical fish and make it a true cold water fish, I guess no.

 

[itrebebag99]

Though there are many fish kills during cold snaps there, it seems enough survive to keep the populations up. And they may be (as skjl47 stated) favoring an ancestral gene that allows survival in colder climates.

 

[itrebebag99]

Though there are many fish kills during cold snaps there, it seems enough survive to keep the populations up. And they may be (as skjl47 stated) favoring an ancestral gene that allows survival in colder climates.

This is really what I was trying to get at with the Miami and Salton sea example, I was trying to point out that if some fish are dying from the cold, while others are surviving, then this must mean either 1.) The ones that died simply went into the cold snap weak, and died of stress (which was an environmental factor, not genetic, or 2.) The survivors had genes that allowed them to survive cold snaps. I would guess that it is the first situation, and the differences were purely environmental, but i don't know.

 

[BIG-G]

Was it ever confirmed that the fish kills were connected to cold temperatures?
Fish kills happen for lots of reasons. Usually they are connected to lack of O2. Whether it be high temperatures lowering the waters abilities to hold on to dissolved oxygen or algae blooms leading to the same.

 

[itrebebag99]

I do not mean that the fish would necessarily be able to survive long, cold northern winters. I just meant making a fish more cold tolerant than it would normally be. Also, I don't think it would take that long for results to be noticeable. For example, in just 30 years, the wings of cliff swallows have gotten shorter to allow them to live under highway overpasses. (https://www.sciencenews.org/article/shorter-winged-swallows-evolve-around-highways)

Plus this is natural selection, which takes a fairly long time. The experiment I was proposing would be much more aggressive, so i don't think it would take an impossibly long time for results to be noticeable.

 

[itrebebag99]

Was it ever confirmed that the fish kills were connected to cold temperatures?
Fish kills happen for lots of reasons. Usually they are connected to lack of O2. Whether it be high temperatures lowering the waters abilities to hold on to dissolved oxygen or algae blooms leading to the same.

Doesn't cold water hold MORE dissolved oxygen, and slow algae blooms?

 

[BIG-G]

Doesn't cold water hold MORE dissolved oxygen, and slow algae blooms?

Correct that's why I ask if the kills were connected to cold temperatures. It's usually high temperatures that lead to fish kills not low temperatures.

 

[BIG-G]

Unless the temperature is lower then is survivable .

 

[skjl47]

The survivors had genes that allowed them to survive cold snaps.

Hello; The issue here is if the gene characteristic is expressed in the phenotype. I believe we all have genes in our DNA that are not expressed in each individual. You may have the capacity to pass on genes for several different eye colors, but can only have one color expressed.

I don't think it would take that long for results to be noticeable. For example, in just 30 years, the wings of cliff swallows have gotten shorter to allow them to live under highway overpasses.

natural selection, which takes a fairly long time. The experiment I was proposing would be much more aggressive, so i don't think it would take an impossibly long time

Hello; The issue here is that this discussion takes in perhaps many thousand individuals over a time. I was under the impression the OP was thinking of making an individual more cold tolerant than it's normal range.