Estuarine fish are those that live in estuaries, the semi-enclosed areas where freshwater rivers meet the ocean and mix, and they are important for coastal fisheries and nurseries. These fish are adapted to a wide range of salinities and can be found in various parts of the estuary, including freshwater, saltwater, and brackish areas.

Freshwater fish are fish species that spend some or all of their lives in bodies of fresh water such as rivers, lakes, ponds and inland wetlands, where the salinity is less than 1.05%. These environments differ from marine habitats in many ways, especially the difference in levels of osmolarity.

Migratory fish, also called diadromous fish, are those that migrate between salt water, brackish water, and freshwater as part of their life cycle, including anadromous and catadromous species.