Fish cultivation involves rearing fish and aquatic products from a young stage using various methods. The fish pen method constructs square or rectangular pens in shallow lakes using nets, bamboo, and wood posts. The fishpond method uses either fresh or salt water in dug or natural ponds. The open-water method cultivates mussels, oysters, and clams in bays, seas, and lagoons. Common fish used for cultivation include tilapia, milkfish, carp, catfish, mudfish, and gourami.