Salmon
There are actually several categories of freshwater/saltwater migratory fish.
Wikipedia breaks them up into several categories: Diadromous, Anadromous, Catadromous, Amphidromous.
See links for more information.
Some predators can also hunt in both saltwater and freshwater.
Sea Lions will enter rivers such as the Columbia River during fish migrations.
Bull Sharks are also known to hunt both in saltwater and in freshwater rivers.
Crocodiles have also been seen miles out to sea, scarily..
Spotted Seatrout,Redfish,Snook,Black Drum,Sheepshead,Flouder,Mangrove Snaper,Tarpon,Ladyfish, Jack Clevalle,Pompano,Permit,Anlanic Bonito, Northern Kingfish,Scup,White Perch,Northern Searobin, Red Drum,Northern Puffer,Spiny Dogfish,Sand Tiger Shark
Salmon, some trout such as rainbow, striped bass, shad, bull shark.
Yes. Some dolphins and some sharks that normally live in saltwater are known to swim upstream, foraging.
Salmon
tae
It lives in both. It is primarily a saltwater fish but does adapt to live in strictly freshwater (not just brackish)
There are both marine (salt water) and fresh water fish in the tropics.
Piranhas are freshwater fish, living in the Amazon basin.Actually they are both freshwater and salt.... Mostly freshwater though!
Potatoes
There are both freshwater and saltwater bass species.
Redfish are fresh water
Freshwater fish need regular water without salt, Marine fish need salt water. Marine fish are more colorful and interesting then freshwater fish but they are a lot harder to look after than freshwater fish. Saltwater fish need more water to swim in and are more fragile than freshwater fish.
Freshwater fish tend to gain water.
Freshwater fish typically live in water that does not contain salt. However, some fish, like salmon, live in the ocean and then travel upstream through freshwater rivers to breed. Freshwater fish can be small, like those found in a home aquarium, or very large fish that live in lakes and rivers.
One of the most common fish that can live in both salt and fresh water is a salmon:)
The guppy is a fresh water fish.
They learn to hold their breath under water.