Eel cat fish or Plotosus found mostly in estuaries and lagoons, and sometimes up rivers in nearly fresh waters. It occurs in the lower parts of rivers in freshwater or brackish water and in coastal seas. P. limbatus occurs in estuaries and along open coasts.it is the only catfish found in coral reefs; it is also found in estuaries, tide pools and open coasts. P. papuensis is found in turbid rivers and swampy lagoons and backwaters.
Interestingly, unlike the freshwater Siluriformes from which it evolved, Plotosus has evolved long ampullary canals in its electrosensory organs (originally termed “ampullae of Lorenzini”, though now the name is not used) as the voltage gradient across the skin is less than in fresh water and so they must extend deeper into the fish where the difference will be more marked in order that the maximal volatage be registered. Such deep canals are found in elasmobranchs, though not in the freshwater stingray Potamotrygon, indicating this time loss of extended canals rather than gain.