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Question Of The Week....
February 20, 2011
8:24 am
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Jarcave
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Can fish adapt?
Can captive breed fish thrive in water parameters that wild ones can't?

This is a discussion I've had with others. I have my own views, but I'd really like to hear the views and opinions of others on this. The question came about when it was suggested that captive bred angel fish are produced in the far east in water conditions that do not match their natural habitat. Some people believe they have adapted to different, non natural water conditions. Others claim it is unnatural and even unethical to produce them this way. Discuss.... /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />

February 20, 2011
9:08 am
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Stefan
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I have a counter-question: Do you think the water in the wild is of the same parameters all year 'round? Basically this partly answers your question. Secondly I have a sudden urge to say 'neon tetra', with which I rest my case ha ha /biggrin.gif" style="vertical-align:middle" emoid=":D" border="0" alt="biggrin.gif" />

On the other hand it gives rise to the question 'Why would want to?'. Fish occur in specific water, with all its variables, for a reason and stay out of others for the opposire reasons.

February 20, 2011
9:10 am
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Mark Duffill
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I think to a degree any fish will adapt to different conditions within reason, I suppose if the fish breed then the young adapt from birth to live in the water they are in so it does stand to reason that after several captive spawnings the fish wont be as needy of the conditions it would have found had it been in the wild.

It is something that I have always said, especially with the likes of discus, some people have trouble with captive bred fish when they put them in tanks with a very low ph, yes that is what wild fish would be used to but very few captive bred fish will be used to such conditions.

I suppose it depends on the individuals, some will see it as the right thing to do to recreate wild conditions, others however will just go for the easier option and then there are those that just look at financial returns.

Many years ago clown loaches wouldnt have taken high ph levels as the vast majority were wild caught, nowadays the vast majority are commercially spawned and in conditions that are a lot less like wild. I am not saying it is right but I have seen some stunning specimens in malawi tanks with ph's well over 8 so that would suggest that they will adapt.

February 20, 2011
9:18 am
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Matt
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Agree with much of that. Many commercially-bred species will thrive in water conditions they'd never encounter in the wild - acidophilic ones like cardinal or Congo tetras, some Apistogramma, etc. spring to mind. Even tiger barbs naturally live in black water.

Chemistry aside the concept of keeping fish at a constant temperature in captivity is at odds with what happens in nature on both a diurnal and seasonal basis and I'm pretty sure is detrimental to some species.

Cake or death?
February 20, 2011
12:29 pm
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Colin
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yes Matt, I have seen it linked to hole in the head for example where it has been said that constant stable unchanging environments stress the fish and are to blame.

Many of a fish's cues to spawn come from sudden environmental changes too.

One example of quickly changing conditions would be of a peat swamp Betta like persephone that is often found in pH 3 and even just under damp leaf litter. Any amount of rain would instantly change the water partly by being comparatively cold and immediately changing the fish from pH 3 to pH 6.5 or so which would be thousands of times less acidic

In most cases fish gradually adapt to changing conditions like the acidification of an aquarium through time. This happens to many people who do not test their water and in softwater areas the pH can sneak down to 4 or 5 with no obvious affect on the fish... until they try to add a new fish which quickly dies!

From experience, softwater acidic fish adapt better to alkaline conditions than the other way round

February 20, 2011
1:13 pm
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MatsP
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QUOTE (Colin @ Feb 20 2011, 12:12 PM) < {POST_SNAPBACK}>
In most cases fish gradually adapt to changing conditions like the acidification of an aquarium through time. This happens to many people who do not test their water and in softwater areas the pH can sneak down to 4 or 5 with no obvious affect on the fish... until they try to add a new fish which quickly dies!

After having been told MANY times that low pH is bad for fish, I was absolutely convinced my (then brand new) pH meter was broken/miscalibrated/plain wrong when my pH came up as 4.0 - all the fish were perfectly happy and absolutely not "suffering". I didn't, at that time, try to add any new fish. But it's clear that acidic water, to many fish, aren't a huge problem.

I spent the next two hours checking my pH meter, but it did seem to be as near correct as I could make out - tap water around 7.5, KH buffer at 8.2, vinegar at 2.2, etc.

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February 20, 2011
7:30 pm
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Sonny Disposition
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I'm inclined to think that they'll adapt to new conditions over generations, but it will probably take time. I don't know of any studies documenting the phenomenon. Anecdotally, I've heard that wild caught discus are much less tolerant of hard, alkaline water than are discus who are the end product of 50 or so years of captive breeding. It would make sense that they would be. As aquarists practicing less than ideal husbandry manage to kill off the less tolerant specimens in their care, only those animals tolerant of less than ideal conditions remain to pass on their genes.

I don't know whether you've seen this news story about the rapid development of pollution tolerance of a small cod species in the Hudson river. When I was a kid in the late 1960s, the nearby Hackensack River was so polluted all that survived there were American eels and mummichog. Tom cod were no where to be found. So I suspect just a few fish with a genetic variant that allowed them to survive PCBs have since recolonized the whole drainage system.

http://green.blogs.nytimes.com.....011/02/18/...rss&emc=rss

February 20, 2011
8:36 pm
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Colin
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could it not be that the levels of PCB have gone down since 1976? I know that many species of fish are now present in UK rivers that were once wiped out by chemicals and are now back since the rivers cleaned up a bit? Specifically salmon and sea trout are now more common in rivers here in the UK which were recently active

February 20, 2011
11:30 pm
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MatsP
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I don't know about any real documentation, but many cory are often hard to breed in the wild-caught population, but the same species in F1 or F2 (or some other Fn) are relatively easy to breed.

I think this is some evidence of the "only those suitable/adapted survive", and there is, presumably, some genetic variability as to whether they tolerate/breed in different water conditions.

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February 21, 2011
12:18 am
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Sonny Disposition
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I don't know.

But this population of fish has a genetic variation that enables them to tolerate extremely high levels of PCBs.

QUOTE (Colin @ Feb 20 2011, 03:19 PM) < {POST_SNAPBACK}>
could it not be that the levels of PCB have gone down since 1976? I know that many species of fish are now present in UK rivers that were once wiped out by chemicals and are now back since the rivers cleaned up a bit? Specifically salmon and sea trout are now more common in rivers here in the UK which were recently active

February 21, 2011
6:38 pm
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Eyrie
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QUOTE (MatsP @ Feb 20 2011, 11:13 PM) < {POST_SNAPBACK}>
I don't know about any real documentation, but many cory are often hard to breed in the wild-caught population, but the same species in F1 or F2 (or some other Fn) are relatively easy to breed.

I think this is some evidence of the "only those suitable/adapted survive", and there is, presumably, some genetic variability as to whether they tolerate/breed in different water conditions.


Would that be due to development of the fry within the eggs? Those with the right genetic make up survive to be the F1s, those without rarely do.

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February 24, 2011
11:59 am
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Jarcave
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OK it's time to come clean. This subject was being debated elsewhere. A couple of individuals were adamant that a fishes tolerance to changing pH levels took centuries. I'm of the opinion that they can change within a few generations.Discus produced in the far east are a prime example. At least in my book anyway!

Does anyone have any examples of fish being released into wild conditions that differ from the water chemistry of their native environment and managing to survive. Other than the Cave and Basin pool in Banff, Canada where sailfin mollies, Gambusia and jewel cichlids have survived since the 70's at the expense of an endemic species. And of course South Florida where at least 34 species of aquarium fish have been illegally released and are known to breed.

February 24, 2011
4:56 pm
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Matt
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QUOTE (Jarcave @ Feb 24 2011, 12:42 PM) < {POST_SNAPBACK}>
Gambusia and jewel cichlids

Both those are in Spain and various other countries, too. Jared I think your question depends on quite a few variables including species, breeding strategy, natural habitat, degree of inbreeding i.e. size of initial reproductive population, etc.

Also don't forget that in nature, particularly in changeable environments such as rivers, pH can vary on a daily, even hourly, basis.

Cake or death?
February 24, 2011
5:02 pm
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Malti
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if a fish manages to breed, in a couple of generations it will adapt, esp if the difference is very minimal and not sudden.

also fish have the advantage of a very short gestation period, thus compared to other animals their adaptation cycle is much more fast - in 2 months livebearers can breed compared to 12-18 months in dogs and more in other bigger animals.

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