Ocean fish cannot survive in fresh water, and fresh-water fish will die in salt water. why’s this?

3 responses so far ↓

• 1 zero_one_gundam // Nov 9, 2008

  dude its osmosis, just like your last question. do you actually attend class and read from the text book or are you relying on yahoo answers for the next 60+ years?

• 2 Daniel H // Nov 9, 2008

  It has to do with the salinity (salt concentration in the water). Just like all animals, even fish need water in their system to live.

  Osmosis always pushes water from areas of high salt concentration to areas of low salt concentration.

  Fresh water fish, who’s bodies have a higher salt concentration than the surrounding water, have water pushed into their body, and thus never have to actively drink water. Salt water fish have the opposite problem, as water leaves their system so they have to constantly drink water.
  This system is highly regulated for the type of water they evolved to live in. Very few fish can live in both fresh and salt water.

  So when you put a salt water fish in fresh water it explodes from the inside out (the rushing water into it’s high salt body causes many cells to burst). When you put a fresh water fish in salt water it essentially dehydrates because of it’s low salt concentration.

  Most fish have a salt concentration close to their adapted habitat so they can avoid having to drink or “pee” all the time, so when put in a different environment, they die.

  Hope that helps.

  -d

• 3 Stevie F // Nov 9, 2008

  Hey people, Lets not forget the Bull Shark. Found 180 miles up the Mississippi River.