Can salt water fish live in fresh water and vice versa? - Quora

Seven Fish That Can Survive in Fresh and Salt Water • Scuba Diver Life
Photo provided by Flickr
Many families of fish contain both fresh and saltwater species. These include the families of toadfish, garpike, bowfin, sturgeon, herring/anchovy, salmon/trout/pike, catfish, clingfish, stickleback, scorpionfish, and flatfish. Indeed, most of the families alive today have both fresh and saltwater representatives. This suggests that the ability to tolerate large changes in salinity was present in most fish at the time of the flood. Specialization, through natural selection, may have resulted in the loss of this ability in many species since then.
Therefore the kidneys function slightly differently between those fish that live in saltwater and those that live in freshwater
Photo provided by Flickr
Most fish that can only tolerate narrow ranges of salinity and are highly sensitive to any changes in the levels of salt to the water in which they dwell. These fish are known as stenohaline species and include goldfish, which can live only in a freshwater environment. Reversely, tuna can exist exclusively in saltwater, according to the NMFS. May 9, 2017 - Euryhaline fish is the type of fish that can live in both freshwater and saltwater. They are special for not every marine organism can do that.
Photo provided by FlickrThere are a number of fish that have this ability
Photo provided by FlickrFishes that live in freshwater tend to have less saline body fluids than their surroundings
Photo provided by Flickr
About half of fishes live in freshwater terrestrial environments such as lakes and streams while the other half live in the oceans. The physiological cost of dealing with differences between saltwater and freshwater is so great that few fishes can tolerate both. Depending on where they live, fishes have complex ways of dealing with excess salt and water accumulation in their bodies. Fishes adapted to both salt and fresh water, including salmon, eels and bull sharks are unusual. Diadromous fishes describe species that spend part of their lives in freshwater and part in saltwater. There are two categories of diadromous fishes, catadromous and anadromous .The fish uses osmoregulation to fight the process of diffusion and osmosis. Conclusion : In conclusion, saltwater fish cannot, under any circumstances live in freshwater, except for the exception of euryhaline type fish. In this presentation, we explained why saltwater cannot live in freshwater; the answer for this statement is osmosis. This is the balance of high concentration and low concentration in the cells membrane. That is why saltwater fish cannot live in freshwater. This is a saltwater fish. This is a freshwater fish. Both fish are stenohaline types of fish. Salmons are able to live in freshwater AND saltwater which therefore makes them euryhaline types of fish.One major factor that separates fish is salt. Some fish cannot live in areas where there is much salt and others need salt in the water to live. However, some fish can live in both saltwater and freshwater!

Freshwater
Freshwater contains much less salt than the ocean. Most ponds, reservoirs, and rivers across North America are freshwater. Some common freshwater fish are bluegills, carp, catfish, crappie, bass, perch, northern pike, trout, and walleye.

Saltwater
Many kinds of fish live in the salty water of the oceans. A fish’s kidney keeps the proper balance of salt in its body. Popular saltwater fish are bluefish, cod, flounder, striped bass (also found in freshwater), sea trout, tarpon, tuna, halibut, rockfish, sea perch, lingcod, and yellowtail.

Brackish Water
An estuary is where fresh water streams and rivers meet the salt water from the ocean. The amount of salt (salinity) changes daily with the flow of tides, rain, or drought. This water is termed "brackish." Changes in the amount of salinity will determine which fish can live in the area. Species found in these waters include redfish, sea trout, snook and striped bass.

Some fish live in saltwater, but swim up streams and rivers to spawn (lay their eggs). These fish are called anadromous fish. They include shad, salmon, and some types of trout.