I know a little about osmotic pressure and didn't think animals could survive long going from one to the other, let alone going from an ocean then swimming all the way up to the mountain streams of the river where they were spawned
2007-06-10 19:52:21 · 5 answers · asked by rob p 1 in Science & Mathematics ➔ Physics
Fish that can live in both salt and fresh water are called osmoregulators and salmon is one example. There is also at least one type of shark that can do the same. They are able to regulate their salt intake through their kidneys and
their gills. Excess water is lost through the gills and excess salt is removed via the kidneys. (difussion and osmosis) If you wish to be pedantic about it, even freshwater contains some salts. There are also a large number of fish which can apparently live in 'brackish water' (water that is somewhere between salty and fresh - http://www.iowas.co.uk/Brackish.html). Check out 'ask a scientist' here http://www.newton.dep.anl.gov/askasci/bio99/bio99295.htm for a more in depth explanation.
2007-06-11 05:52:09 · answer #1 · answered by isobels_mum 1 · 0⤊ 0⤋
You have the answer for salmon but let me clarify on Bull Sharks. They are known to live in fresh water. Lake Nicarauga has a population and is or was known as the only lake to have sharks. Bull sharks are also known to swim far inland up rivers and have attacked people several miles into fresh water
2007-06-17 20:43:11 · answer #2 · answered by Charles C 7 · 0⤊ 0⤋
Salmon are not "Brackish" fish as said in some of the other answers and are not truely able to live in both enviroments.
Salmon undergo massive physiological changes when they embark on their freshwater journey. Also they do not eat anything once they leave the sea, instead useing fat reserves built up during their natural saltwater lifetime.
Eventually after reaching the end of their journey and breeding, they die because they cannot as you say live for long in a freshwater enviroment.
2007-06-12 13:50:36 · answer #3 · answered by B-A 1 · 0⤊ 0⤋
Scats, mono's, aruis seemai are popular aquarium 'brackish' fish. Mangrove swamps are very productive brackish enviroments. You also find Archer fish, awanas' (spelling?) and mudskippers living in lightly salted water.
I think its the bull shark that can live (for a short period) in brackish water. Check out the story that inspired the book which inspired the film Jaws for the exact make/model of shark.
You find salt in the great rift lakes - obv not the same as sea salt though.
2007-06-12 02:54:00 · answer #4 · answered by Chris O 2 · 0⤊ 0⤋
They stop along the way and slowly adapt to the fresh water as they are making their way to where they spawn.
2007-06-10 20:02:22 · answer #5 · answered by peterismypal8 2 · 0⤊ 0⤋