what makes physically impossible for salt water fishes to live in freshwater and vice-versa?

Answer 1

Fish also drink water, and use kidneys to excrete excess salt. Kidneys only work within a specified range of salinity. Very few fish have kidneys that can handle both fresh and salt water.

Incidentally, I've always wondered how creationists explain the ability of all fish and other aquatic life on the planet, to have survived Noah's flood ... i.e. in the same water that covered the earth for almost a year. They seem to believe that 'water is water', and trout, tuna, goldfish, koi, minnows, freshwater bass, saltwater bass, squid, sponges, jellies, lobsters, etc. etc. can all survive in the same kind of water ... or pehaps they can survive in *any* kind of water. But as your question illustrates, this is trivially false.

Answer 2

The skin of fishes is a semi-permeable membrane--water can pass through, but not salt. Saltwater fish are used to living an enviornment where the salt in the water is greater than their bodies, so they are constantly having to deal with water leaving their bodies through the semi-permeable membrane to even it out. Freshwater fish are used to compensating for being more salty inside than outside. Under the other circumstances, freshwater fish in saltwater will dry up, and saltwater fish in freshwater will explode.

Answer 3

Because Salt water fishes are not fresh water fishes and vice versa

Answer 4

Some fish, like salmon, born in fresh, die in fresh live most of their lives in salt water.
Their body's under go a physical change triggered by the salt water and then again by the fresh in order to endure the changes.
Pacific salmon, die after breeding, Atlantic salmon return to the sea and continue to live, unless they get caught and eaten.

Answer 5

salt water fish have learnt to live salt solution while freshwater fish are incapable of tolerating a salty environment.

hypertonic solution is sea water and causes dehydration - sea fish have mechanisms to overcome this.

Answer 6

see the fish can tell what is saltwater and what is fresh water and if u but a fish that lives in salt water and but it in the lake that has fresh it wont live because it wont be able to adapt that quick

Answer 7

Osmosis the movement of water from an area of high solute concentration to an area of low solute conc.

The fish have modifications to stop water "drowning" them or dehydrating them e.g gulping lots of extra water or excreting very diluted products.

Answer 8

salt water fishes have adapted to the salt so their bodies need it now to survive. It's like putting you on mars. You'd suffocate from no air.

Answer 9

Nope...The fish would die eventually in the wrong habitat

Take the salmon for example. They come from the ocean to spawn in freshwater...most of them die eventually because of lack of saltwater

Answer 10

i think there is a difference in oxygen...also i think the difference in the food chain an living spaces has sumthin to do with it