why cant saltwater fish live in fresh water..vice versa..answer a.s.a.p..please!!!!need this tonight!!!!?

Question

i have a school project to do and i need to know the answer to this a.s.a.p..

Answer 1

It's to do with osmotic pressure. The pressure of fluid moving from one area to another due to density or dissolved solids. In salt water, the water has more dissolved solids in it that the water in the fish, so water is constantly moving into the fish. Just the other way around in freshwater. Each kind of fish is able to handle water going in one direction, but not the other. There are a few fish, like Bull sharks and Salmon, that can handle both ways, but not very many. This is true for most all organisms that live in water, including fish, plants, crustaceans and even small animals like parasites. Here's a link to an article about it.

http://www.aquariacentral.com/articles/osmoregulation.shtml

Hope that helps

MM

Answer 2

It has to do with their bouyancy. Saltwater fish will sink directly to the bottom in a freshwater aquarium while freshwater fish will bob on the surface. They cannot handle the differance in the specific gravity of the water. The rapid change in specific gravity is what actually kills them.

You can actually get fish to survive in a very differant specific gravities and salt levels of water for a while if the salt content is lowered slowly over a few days. Or raised very slowly over a matter of weeks.

I have kept saltwater fish alive at a specific gravity of 1.009 for over a month before raising it back up. I've never tried freshwater at a salinity near saltwater though but I would assume it could be done as long as they can tolerate the salt in the water.

Answer 3

Many saltwater fishes can live in brackish water, but no more than that. If you put them in fresh water, their body absorbs the water, there is not enough outside osmotic pressure to prevent it happening. The reverse is true of freshwater fish that in the main would dehydrate.

Answer 4

Saltwater fish have had their cells adapted to the high concentration gradient of salt. If salt water fish lived in freshwater fish they would drown from all the excess water. And freshwater fish have had their cells adapted to freshwater, if they lived in a saltwater environment their cells wouldnt get enough water and they would suffocate or something like that i took this in biology 1 year ago

Answer 5

It has to do with osmoregulation. The cells of saltwater fish are designed to actively transport excess salt out and water in. The cells of freshwater fish are designed to actively transport salt in and water out. Too much salt inside a cell, and the cell bursts; too much salt outside a cell, and a cell shrivels. This is because water travels from areas of low solute (salt) concentrations to areas of high solute (salt) concentrations.

Answer 6

Think of it like our air quality. Freshwater is much denser. Compare Freshwater to the air we breathe at sealevel. To compare to saltwater, someone would have to climb past the top of Mount Everest, without using an oxygen pack. It would be very hard, impossible to breathe up there. But say someone lives up there who has adapted to the air. That's the saltwater fish.

Answer 7

it all depends on the fish for example bull sharks can live in both fresh and salt. heres an intresting fact for your projecet. in an aquarium freshwater fish like a little salt in the water. The salt helps clean out thier gills and releave stress on the fish. there is a difference in salt thou for fresh i use aquarium salt and for sea water they use sea salt. why i realy dont know but for a guess the fish just get stressed out and die? all what i know for shure is the fact

Answer 8

It believe it has to do with the way they regulate the salt balance inside their bodies.

Some fish, such as mollies, have been known to survive in full freshwater and full saltwater, as well as brackish (they are a slightly brackish fish).

Answer 9

because they come from different parts of the world, which has different temperatures and different levels of salt

Answer 10

no. they would die.