Fish species that can survive in saltwater, as well as freshwater, are called Euryhaline fish.
They can actually survive a wide range of salinity.
The anadromous fish, one of the euryhaline fish, spend most of their lives in the sea and return to freshwater for spawning.
So, given below are 8 saltwater fish species that can also live in freshwater.
1. Salmon
Salmons belong to the family Salmonidae and are euryhaline ray-finned fish.
They inhabit the waters of the North Atlantic and North Pacific basins.
Salmons are the most well-known among the anadromous fish species.
Most salmons start their lives in shallow freshwater streams and migrate to the oceans once they grow up.
Then, they continue to live like saltwater fish, returning to freshwater only when it’s time to reproduce.
It’s also observed that salmons return to the place of their birth to spawn.
In the wild, you can find one species of Atlantic salmon and six species of Pacific salmons like the Chinook, Chum, Coho, Masu, Pink, and Sockeye found in North American waters.
Salmon usually eat a wide range of marine life, including lanternfish, herrings, sand lances, and barracudina.
They also eat small invertebrates like krill, squid, and polychaete worms.
2. Smelt
Smelts are small-sized fish that belong to the family Osmeridae.
They are also known as freshwater smelts or typical smelts.
These fish are commonly found in the waters of the North Atlantic and North Pacific oceans.
They also inhabit the lakes, rivers, and streams of Europe, North America, and Northeast Asia.
Like salmons, many smelt species are anadromous.
This means they spend most of their lives in the sea but travel to freshwater rivers and streams to breed.
Smelts are a vital food source for many marine fish species like salmon, striped bass, and lake trout.
There are 14 different species of smelt fish in the Osmeridae family.
The diet of these fish changes based on their natural habitat. However, they usually feed on crustaceans like krill and shrimp.
They also eat fish eggs and larvae, insect larvae, and plankton.
3. American Shad
The American shads belong to the family Clupeidae.
These fish inhabit the waters of the North American coast of the North Atlantic.
An American shad spends most of its life swimming in saltwater, but it travels upstream into freshwater to lay eggs.
The northern fish populations of the American shads are iteroparous.
This means they reproduce more than once in their lifetime.
So they travel between the sea and freshwaters to lay eggs several times.
The shads are known to filter their feed at sea by first opening their mouth and taking in everything that comes inside.
Then, they filter out parts that they don’t want to eat.
American shads primarily feed on plankton but eat tiny shrimp and fish eggs too. They occasionally also eat small fish.
4. Striped Bass
The striped bass, also known as the striper, Atlantic striped bass, or rockfish, belongs to the family Moronidae.
These fish are native to the Atlantic coast of North America.
They are recognized as the state fish of Maryland, Rhode Island, and South Carolina in the United States.
Like other anadromous fish, the striped bass migrates from the saltwater of the Atlantic coastline to freshwater rivers and streams to breed.
The striped bass is introduced into the waters of many countries like Ecuador, Iran, Latvia, Mexico, Russia, South Africa, and Turkey for aquaculture and sport fishing.
These fish are opportunistic feeders and eat a wide range of baitfish, including bunker, herring, and mackerel.
They also prey on invertebrates like clams, crabs, eels, shrimp, and squid.
5. Sturgeon
The sturgeon fish belongs to the family Acipenseridae. There are 27 fish species that belong to this family.
Sturgeon fish are native to the temperate, subtropical, and sub-Arctic rivers, lakes, and coastal parts of Eurasia and North America.
Most sturgeon fish are anadromous.
Meaning they spend most of their lives in marine environments near coastal areas and open oceans but migrate upstream to spawn in freshwaters.
Several species of sturgeon fish are harvested for their eggs which are used for making caviar, a luxury food item.
These fish are benthic feeders that eat shellfish, crustaceans, and small fish in the wild.
However, some sturgeon fish mainly prey on marine fish once they grow up.
6. Bull Shark
The bull shark is also known as the Zambezi shark, zambi, or Nicaragua shark. This fish belongs to the family Carcharhinidae.
The bull shark inhabits warm and shallow waters around the globe.
They are commonly found in brackish and freshwater environments, including estuaries and lower reaches of rivers.
These euryhaline fish can survive in both saltwater and freshwater environments.
However, they aren’t considered actual freshwater sharks despite being capable of surviving in freshwater habitats.
Bull sharks can quickly adapt to both freshwater and saltwater habitats.
However, these fish prefer to live in marine environments as their food source consists of saltwater fish and invertebrates.
Bull sharks mainly feed on bony fish and small sharks, including other bull sharks and stingrays.
They also eat birds, dolphins, terrestrial mammals, turtles, crustaceans, and echinoderms.
7. River Herring
The river herring belongs to the family Clupeidae. There are two species of river herring, the blueback herring and the alewife.
These fish are anadromous because they live most of their lives in saltwater and return to freshwater rivers, streams, and lakes to lay eggs.
Unlike salmons that typically pass away in freshwater rivers and streams after spawning, herrings return to the marine environment and make several trips to freshwaters in their lifetimes.
These fish primarily feed on zooplankton. They play a crucial role as a food source in marine and freshwater ecosystems.
The river herrings become prey to several fish, birds, and mammals.
They are a food source for seabirds, herons, ospreys, eagles, tunas, trouts, cods, raccoons, weasels, turtles, etc.
8. Trout
Trouts belong to the family Salmonidae. They can be found throughout North America, Northern Asia, and Europe.
Many species of trout are anadromous, while the most well-known anadromous trout is the rainbow trout.
Like other anadromous fish, some trouts live most of their lives in marine environments and return to freshwater habitats to reproduce.
However, trouts return to saltwater environments and migrate several times to freshwater habitats in their lifetime.
Trouts primarily feed on other fish and invertebrates, like flies, caddisflies, mayflies, dragonflies, stoneflies, and mollusks.
