The primary difference would be in the salinity of the the water which in turn changes the ecosystem and supports different life forms. Both will support a different variety of fish and wildlife and can thrive in the proper environment.
One of them lives in fresh water and the other in salt water.
Distilled water is only H2O (ideally). Fresh water contains whatever it picks up from the stream bed ... including fish and animal waste.
Most sea fish have sharp teeth and most river fish have no teeth
Both fresh water and salt water occur in nature, so both are natural. Note, however, that fish that live in fresh water generally cannot survive in salt water and fish that live in salt water generally cannot survive in fresh water.
The difference is all fish stay alive in different types of water warm,cold,fresh, salty. They do different things in different water
Because marine fish live in salt water because there found in the ocean.
Brackish?
because there is a difference in salinity which means less salt there is alot less in fresh water
Both kinds of fish can live in a delta area. The line between salt water fish and fresh water fish seems to be getting blurrier. Sharks and other typically salt water fish are found many miles up stream in rivers that empty into the ocean. It appears that salt water fish adapt better than fresh water fish as the fish found in fresh water are not found out at sea.
Fresh water
fresh water .my fish are 16 yrs old
Fresh water fish survive just as well as fresh water fish. Maybe this question isn't the one that you actually meant to ask?
Rivers,lakes.ponds,any fresh water source or there are fresh water fish breeders