There are several fish species that can survive in both freshwater and saltwater environments. These fascinating creatures are known as euryhaline fish (eurysaline - wide salt range). They possess special adaptations that allow them to regulate their internal salt and water balance regardless of the surrounding water's salinity.
Here are some examples of euryhaline fish:
- Salmon: Perhaps the most iconic example, salmon are born in freshwater rivers, migrate to the ocean as adults, and then return to freshwater to reproduce. They can adjust their physiology to thrive in both environments.
- American Eel: Another migratory fish, American eels spend most of their lives in freshwater but return to the Sargasso Sea in the Atlantic Ocean to spawn.
- Bull Shark: This aggressive shark is known for its ability to tolerate a wide range of salinity levels. They can be found in freshwater rivers, estuaries, and even out in the open ocean.
- Striped Bass: Popular sport fish, striped bass can live in both freshwater and saltwater environments. They are commonly found along the Atlantic coast of North America.
Euryhaline fish have evolved various mechanisms to handle changes in salinity:
- Osmoregulation: They can actively control the flow of salts and water across their gills and body membranes.
- Kidney Function: Their kidneys play a crucial role in excreting excess salts or retaining water as needed.
- Specialized Cells: Some species have specialized gill cells that help them pump salts in or out depending on the surrounding water's salinity.
