Fish Adaption To Acidity Levels

[Martin e]

Hello Everyone

I posted a question - reproduced below - yesterday on the general discussion board and the suggestion was made that it might be best to post it here because of its scientific nature. My original post was:

I’m interested in trying to understand the science behind the adaption of fish to acidity levels. Some fish species are able to live in water that is effectively poisonous to other fish species. For example, a fish adapted to thrive in relatively acid water conditions might not even survive in alkaline conditions and similarly a fish adapted to alkaline conditions might perish in acidic water. My question is why? What are the key differences between the species that can survive acid conditions and those that can survive alkaline conditions?
Are the differences structural, for example difference in design of gills or such like, or are the adaptions biochemical such as the fish having enzymes that can perform the necessary chemical processes, or is it a mixture of the two?
I believe that water acidity can affect what nutrients are available in the water so how does a species of fish overcome a lack of such nutrients? Is it able to somehow extract the nutrients that other fish cannot extract or does it adapt by making do without such nutrients; perhaps substituting different nutrients to make up for the deficit?

Thanks for your interest and any advice you are able to give.

Martin

 

[TwoTankAmin]

I can supply part of the answer but not quite as scientifically as you might want.

1. Alkaline water is typically harder whereas very acid water is normally very soft. They have way different TDS levels and TDS levels are central to osmotic regulation. FW fish use osmoregulation to balance water and ion flows into and out of their bodies. Moving a fish adapted to low tds into high tds or vice versa is usually fatal as the fish is unable to adapt the osmoregulatory process quickly enough.

2. Bacteria have difficulty living in acid water. As a result fish who come from very acid waters have a lower resistence to certain diseases as their immune systems are not well developed to cope with those bacteria. This is why it is so difficult to keep fish like altum angels alive when they are newly imported from the wild. It take a few months of weening them over to tap water for their immune systems to rebuild their defenses against such things.

As for what other factors may be at work in terms of high vs low pH I am not sure as I am not well enough educated on this topic to get beyond 1 and 2 above. Hopefully somebody with better scientific knowledge than mine will also chime in.

ps- If you want to see a 12 min vid of a low pH environment (and don't mind it being narrated in German) see this thread http/www.fishforums.net/index.php?/topic/363439-altums-and-more-in-the-wild/ The pH there is as low as 5.5 in dry season but varies from 5.8-6.5 during the rrest of the time. TDS are low the water and the water hardness is below 1dg.

 

[Bignose]

You are probably going to have to consult some ichthyology texts for this more detailed information. Maybe even have to pull some source articles. I have read and can recommend Moyle and Cech's fishes" An Introduction to Ichthyology. I know it has some info in there about responses to changes in pH -- it is where I got my number for how quickly a fish can change its internal fluids' pH. I am sure there is info either in the text or in the sources it cites to answer your specific question.