Cua Dai Estuary

Cua Dai Estuary is the large estuary where the Thu Bon River reaches the South China Sea near the city of Hoi An in Quang Nam Province, central Vietnam. Its name, Cửa Đại, means "Large Estuary" in Vietnamese. The estuary forms the final section of the Vu Gia–Thu Bon river system and is one of the most important coastal ecosystems in central Vietnam. It is strongly influenced by tides, creating a dynamic environment where freshwater and seawater.

The estuary receives freshwater primarily from the Thu Bon River and is hydrologically connected with nearby waterways, including the Truong Giang River. Extensive sandbars, mudflats, mangroves, and tidal channels provide important habitat for fish, crustaceans, mollusks, and migratory birds. More than 100 fish species have been recorded in the estuary, highlighting its high biodiversity and ecological importance.

Cua Dai Estuary is an important fishing area supporting both commercial and recreational fisheries. Common species include Barramundi (Lates calcarifer), Mangrove Jack (Lutjanus argentimaculatus), Indo-Pacific Tarpon (Megalops cyprinoides), mullets (Mugilidae), threadfin breams (Nemipteridae), croakers (Sciaenidae), gobies (Gobiidae), and numerous marine and estuarine species that use the estuary as a nursery and feeding ground.

Besides its ecological value, Cua Dai Estuary has played an important role in the history of Hoi An, serving as the maritime gateway to one of Southeast Asia's most significant trading ports. Today it remains an important navigation route, fishing ground, and natural link between the Vu Gia–Thu Bon river system and the South China Sea.