Osmotic regulation in fish?

What osmotic regulatory challanges whould a fish living in freshwater have verses a fish living in salt water?

2 Answers

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  • 1 decade ago
    Favorite Answer

    Fish flesh is saltier than fresh water, but less salty than sea water.

    Osmosis would then tend to have water go in the fish in fresh water, and to dehydrate the fish in sea water.

  • Parnel
    Lv 4
    4 years ago

    This sounds like a homework problem, and out of principle I will not do any body's homework for them. However, I don't have any problem pointing people in the right direction for their homework (I needed it from time to time as a college student myself). The difference between salt water and fresh water is the occurrence of salt, NaCl. Salt soaks up water. That's why there is a packet of it in the bottom of aspirin bottles. The salt soaks up water in the bottle, keeping your aspirin from mildewing, etc. Therefore, in marine fishes, where their surroundings have a higher salt content than their bodies, there is a constant battle against dehydration. Marine fish must be able to retain water. Freshwater fishes, however, have the opposite problem. The salt content of their bodies is higher than the surrounding water. Therefore, they constantly fight a battle to get RID of water. This explains why most fish can't change between fresh and salt water environments. Freshwater fish would turn into raisins in a marine environment, and marine fish would explode from having too much water retention (although there are a few species that go between the two environments quite well). This is half of your answer. I compared the osmotic problem for you. I leave the mechanism up to you, but I hope this helps. Good luck!

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