Seining and draining are the two main methods of harvesting catfish from pond farms. Draining is an effective method as it allows better management of pond soils, but in areas where refilling the ponds requires pumping it involves an additional major cost. Also, there appear to be some practical difficulties in synchronizing the completion of draining with the delivery time of the fish to live haulers. Seining has an advantage in this respect and it also permits partial harvesting. If the mechanized seining equipment described is used, labour requirements can be reduced. However, larger investments for equipment are required and complete harvesting will not be possible. In recreational waters, channel catfish are caught by hook and line, using an ordinary fish hook on a pole, trotline or spinning rod.
After harvest, the fish may have to be held for several days before marketing. Vats, tanksor small ponds are used for holding. The fish have to be fed at maintenance levels if the holding period is longer than a day or two. If large harvests are involved, some culturists use ‘live cars’ (rectangular enclosures of netting buoyed by a series of floats) into which the catch from a seine can be transferred through a framed opening. The live car itself can be opened or closed by means of a drawstring. The problem of off-flavours developed by catfish in ponds and methods of eliminating them have been referred.
Catfish are usually hauled in tanks made of wood, fibreglass or aluminium. About 1kg fish can be hauled in every 5l water, with a change of water every 24 hours. Devices for aeration are installed in the tank. In most cases, agitators that stir the surface water suffice. Deep tanks may, however, need aeration from the bottom.
Catfish are marketed as whole fish, dressed fish or steaks and fillets. The dressed or pan-dressed fish is the most popular product, with the viscera, skin, head and some of the fins removed. Fish of 500–650g are well suited for this type of product. For steaks, larger fish of about 900g or more are used. Fillets are made from small or large fish. Usually such processing and packaging is done in either farmer-operated facilities or in large processing plants.
The product is packaged for quick-freezing or for marketing fresh, wrapped in polyethyl-ene film or bags. Frozen fish are stored at -1 to 1.7°C before sale.
As in all types of aquaculture, the economics of catfish culture show considerable variations between farms, depending on the locationand culture system employed. Available data indicate that under prevailing conditions, pond farming is probably the most profitable system, although production up to fingerling stage only may sometimes give a better profit. Larger farms are more profitable than smaller ones. Production has to be at least 1500–2200kg/ha to make a reasonable profit. The benefits of double-cropping with trout have been discussed on trout farming. Some farmers rotate rice, catfish and soybeans to yield better returns. The agronomic crops benefit by the improved nutrient level of the soil, caused by the accumulation of excrement and unconsumed feeds during fish culture.