A thesis submitted in partial fulfillment of the requirement for the degree of Master of Science

Thesis (M.Sc.) - Asian Institute of Technology, 1991

An experiment on integrated walking catfish-tilapia culture was conducted for 3 months. Twenty-five, 50, 100 and 150 walking catfish were stocked in each of the 1.2 m3 cages integrated with tilapia culture in 12 outdoor static concrete tanks. To produce 1 kg of live catfish generated 48.0-60.0 g nitrogen (N) and 10.0-12.5 g phosphorus (P) as metabolic waste. Approximately 65-70 % of the total N and 56- 63% of the total P input from the feed were released in the tank from which 4-13% N was recovered in tilapia biomass; 23-35% of N was accumulated in the sediment, and 7-12% remained in the water column, and 16-64% N was unaccounted for. About 37%-44% of P from the feed was incorporated in the catfish, and 5-17% P was used in tilapia production. Considerable amount of P (34-51 %) settled to the tank bottom. Most of the P loss was accounted for. A stocking ratio between walking catfish and tilapia of 2.5 was the most appropriate, which resulted in the best tilapia growth with an extrapolated production of 9.5 tons/ha/yr. However, the stocking density of catfish used in the present experiment did not seem to significantly affect individual catfish growth. Integrated culture with stocking ratio between catfish and tilapia of 2.5 and 5 improved the water quality which was supported by Lin (1990). However, higher ratio (> 10) resulted in extra phytoplankton bloom, and instability of the culture system increased as water quality worsen.