Yes, some freshwater species can live in brackish water.
While most freshwater fish are adapted to environments with very low salinity and marine fish are adapted to high salinity, brackish water represents a transitional zone with salt levels higher than freshwater but lower than seawater. The ability of a fish species to survive in brackish water depends heavily on its physiological adaptability, particularly its ability to regulate the balance of salt and water within its body (osmoregulation).
Which Freshwater Species Can Tolerate Brackish Water?
According to available information, some freshwater species are hardy enough or survive better in brackish water. These species possess the physiological mechanisms necessary to cope with fluctuating or elevated salinity levels that would be lethal to many other freshwater fish.
Examples of freshwater species known for their tolerance or preference for brackish conditions include:
- Polypterus bichir (Bichir)
- Certain loaches
- Danio rerio (Zebra Danio)
- All kinds of mollies, particularly the Yucatán molly
- Some gobies
This highlights that while not all freshwater fish can make the transition, a notable group of species demonstrates a remarkable capacity to thrive outside strictly freshwater environments, venturing into or preferring the unique conditions of brackish habitats like estuaries, mangrove swamps, or coastal lagoons.
