Techniques for integrating aquaculture with agriculture on irrigated farms: Pulsed flow culture systems.

Abstract

The objective of this dissertation was to evaluate the feasibility for integrating aquaculture with agriculture on irrigated farms. I developed a pulsed flow culture procedure for culturing fish in irrigation ditches where water was replaced once daily. Water from the fish culture operation was than used to irrigate ornamental trees (mesquite) for sale to the nursery industry. Twelve and four tenths percent of the channel catfish survived the 90 day experiment whereas 88.5% of the tilapia survived. These differences were statistically (P < 0.05) significant and may indicate that red tilapia are better suited than channel catfish for culture in pulsed flow culture systems. Densities of 10 and 20 tilapia/m³ showed the best performance among the five densities (10, 20, 30, 50, and 70 fish/m³) tested. Water quality limited the density of fish that could be cultured in this type of pulsed flow culture system. Ammonia concentrations and levels were periodically high (5 ppm) and dissolved oxygen levels were periodically low (1.5 ppm). Each 100 meters of ditch could potentially produce between 240 kg and 420 kg of tilapia per growing season. In all treatments, the length and weight of red tilapia predicted by Santos' equation closely followed the empirical data. There was a significant difference (p ≤ 0.001) in the growth (height and stem base area) of mesquite trees irrigated with well water and those irrigated with water that was from the fish culture facility. Trees of the size produced with water from the fish facility could be sold after about six months for prices ranging from $5.50 to $8.50. Trees irrigated with well water would take twice as long to reach a marketable size as those irrigated with water used for fish culture. The integration of aquaculture with agriculture using pulsed flow culture systems seems to have the potential to increase cash flow from irrigated farms. The production of fish and ornamental trees with the same water used to irrigate agronomic crops seems biologically, technically, and economically feasible.