Goa’s ecosystems are sustained by 11 rivers – Terekhol, Mandovi, Baga, Zuari, Colval, Saleri, Mandre, Harmal, Sal, Talpona and Galjibag.
These rivers sustained the earliest civilizations in the area, which is evident from the discovery of rare Stone Age carvings on the banks of the Kushavati and Zarme rivers.
All 11 rivers originate in the Western Ghats and drain into the Arabian Sea.
Of these rivers, the Mandovi contributes the most to the population of the state.
Throughout the course of these rivers, there are canals, lakes, bays, lagoons and creeks, which are interconnected via wetlands, tidal marshes and cultivated paddy fields.
Goa’s rivers have a very low flow during the non-monsoon months due to various reasons including narrow width of the state, steep slopes of the Western Ghats, non-uniform distribution of rainfall, porous sub-stratum etc.
Major brackish water fish of saline areas include prawns, mullets, pearlspot, catfish, milkfish, sea bass, Epinephelus sp, Lutjanus spp, Sillago spp, Ambassis sp, estuarine crab and molluscs.
A 2014 study revealed that there are 40 species of freshwater fish, 7 species of crustaceans and 2 species of molluscs.