What Happens When...

[OneOnion]

What happens when a freshwater fish is put in a saltwater tank and if a saltwater fish is put in a freshwater tank? I'd never do this, I was just wondering what happens and how they die if it happens.

 

[cheesy feet]

I know that saltwater fish drink water and then flush it out through their body, making their urine concentrated, whereas fw absorb water.There's a pinned article on it......Here
http/www.fishforums.net/index.php?showto...rom+Freshwater/
Obviously a fw fish for starters wouldn't be able to absorb saltwater well.

 

[Buddyboy67]

Osmosis comes into play and the fishes body fluid levels get disrupted..destroying organs and blood.

 

[OneOnion]

I know that saltwater fish drink water and then flush it out through their body, making their urine concentrated, whereas fw absorb water.There's a pinned article on it......Here
[URL="http/www.fishforums.net/index.php?showto...rom+Freshwater/"]http/www.fishforums.net/index.php?showto...rom+Freshwater/[/URL]
Obviously a fw fish for starters wouldn't be able to absorb saltwater well.

Thanks, that was an interesting article.

Osmosis comes into play and the fishes body fluid levels get disrupted..destroying organs and blood.

Ouch... *shivers* sounds painful. Lol

 

[andywg]

I know that saltwater fish drink water and then flush it out through their body, making their urine concentrated, whereas fw absorb water.There's a pinned article on it......Here
[URL="http/www.fishforums.net/index.php?showto...rom+Freshwater/"]http/www.fishforums.net/index.php?showto...rom+Freshwater/[/URL]
Obviously a fw fish for starters wouldn't be able to absorb saltwater well.

I would dispute much of what was written there. It seems they have understood part of the osmoregulatory process, but not really thought it all through regarding whether a SW fish is more susceptible to pollutants than FW; especially considering the below extract I came across:

Acute toxicity levels (lethal concentration to 50% of test orrganisms after a 96 hour exposure) range from 0.068 to 2.0 mg/l for freshwater and from 0.09 to 3.35 mg/l for marine fish (from Handy, R D and Poxton, MG 1993. Nitrogen pollution in mariculture: Toxicity and excretion of nitrogenous compounds by marine fish. Rev. Fish Biol. Fisheries 3:205-241).

An interesting debate was had between TommyGun and myself in this topic. In my opening post I set out some of the science on osmoregulation (from Fishes: An Introduction to Ichtyhology 5th Edition, by Joseph J Cech Jr and Peter B Moyle):

Osmoregulation in Marine Teleosts

Marine teleosts maintain a total ionic concentration in the plasma of approximately one third that of sea water. Most of the ions the fish will want are contained in sea water, so the principal feature of osmoregulation is actively to secrete sodium and chloride based ions into the water while "drinking" (ingesting into the stomach) large amounts of sea water to counteract the continual loss of water from the fish's blood at the gills.

The fish have special chloride cells in the gill filament and opercular skin epithelia to eliminate much of the excess salts through the aforementioned active transport. Marine teleost kidneys cannot produce a urine more salty than the blood (Schmidt-Nielson, 1975) and as such cannot utilise the marine elasmobranch method of osmoregulation which involve retaining a high concentration of organic salts to prevent the inorganic salts flooding the body. These organic salts are primarily urea and secondarily trimethylamine oxide at a ratio of 2:1.

Osmoregulation in Freshwater Teleosts

Freshwater teleosts tend to maintain an internal level of salts between a quarter and a third of the salt concentration of salt water (so less than marine fish, but not by a huge difference). However, the water they live in tends to have a Total salts level of 1-10 mOsm/L instead of sea water with around 1,000.

As can be seen, the problem for freshwater teleosts is not retaining water, but rather retaining salts and preventing the water entering the body from pushing out the salts to a point where the fish can no longer operate at a cellular level (internal drowning).

Freshwater telosts manage this through producing continual low salt dilution urine which is nigh on constantly being passed by the fish. The active transport in freshwater teleosts is in uptake of salts, rather than the expulsion seen in marine teleosts.

So if a FW fish (which is expert at retaining salts) is dumped into SW, expect it to retain too much salt making it hyperosmotic. A SW fish will take on too much water and become hypo-osmotic.

 

[cheesy feet]

Interesting...Goes off to read other thread.