Managing water quality in channel catfish ponds

Excerpt

CHANNEL catfish farming in the United States has expanded rapidly in the past decade, and yields of fish have increased dramatically because of higher stocking and feeding rates. Environmental problems in culture ponds are increasingly common because metabolic wastes accumulate as feeding rates increase. Organic wastes exert an oxygen demand. Inorganic wastes, particularly nitrogen and phosphorus, favor greater phytoplankton growth, which, in turn, contributes to oxygen demand. Demands for oxygen may become so great that dissolved oxygen concentrations are too low for fish. Carbon dioxide, ammonia, and nitrite also accumulate, occasionally reaching concentrations harmful to fish. Water quality thus becomes the limiting factor to fish production.

Controlling phytoplankton blooms

Daily feeding rates are calculated as percentages of the weights of channel catfish in ponds (2). As fish grow, feeding rates are increased. Maximum feeding rates are normally attained in late summer or early fall.

The quantities of metabolic wastes reaching pond waters and the abundance of phytoplankton increase in proportion to feeding rates (7 …