from use of copper-based pipes and other materials. It is best to use plastic pipes, coated screens, and other non- metal equipment whenever possible. Catfish are very sen- sitive to chlorine, so treated municipal water (usually con- taining < 2 ppm chlorine) should only be used if first dechlorinated with 7 ppm sodium thiosulfate to 1 ppm chlorine. Pesticides must always be used with extreme caution. Salinity concentration of water is of special concern to farmers drawing their water supplies from coastal areas. Channel catfish can withstand salt in small amounts, but salinity should be checked if high levels are suspected. Channel catfish can tolerate salinities up to 12 parts per thousand (o/oo), but they will not breed if the level is over 7 o/oo (full strength sea water is about 30-35 o/oo). Higher salinity levels may result in physiological stress. Avoid abrupt changes between fresh and salty water. Stocking Catfish can be stocked in the late fall, winter, or early spring. Summer stocking must be avoided since high water temperatures and low oxygen in hot weather greatly increase stress and the possibility of death due to suffoca- tion, disease, and other factors. If possible, avoid mov- ing or handling fish in the afternoon and avoid drastic changes in water temperature. Fingerlings for stocking should be moved as quickly as possible in well aerated containers (see "Transporting Fingerlings"). The number of fish to stock depends on many factors, including water quality, size and efficiency of facilities and equipment, length of the growing season, feeding schedule, and size of fish desired for marketing. In general, fish are stocked according to the surface area of the water. If fish are not to be fed, stocking densities in ponds should not exceed 100-200 fish per surface acre. Fingerlings (4-8 inches) can be stocked in ponds at den- sities of 1,000-3,000 or more fish per acre and harvested in one to two seasons if feeding is planned. Raceways can be successfully stocked with as many as 2,000 fingerlings per 100 foot section when optimal water conditions ex- ist. Initial stocking densities of 12 fingerlings per cubic foot of cage are possible. Regardless of the facilities used and degree of management intensity, lower stock- ing densities reduce risk of losses to oxygen shortages, parasites, and infectious diseases. Fewer fish should be stocked in waters that may become very hot in the sum- mer or that have excessive water quality and weed prob- lems. Higher stocking densities result in smaller fish at harvest if they are not fed at the same rates as fish stocked at lower densities. Water quality becomes limiting at high feeding rates. Prudent managers are aware of the limits of their facilities, equipment, and water conditions and stock fish at densities that are appropriate to their harvest goals. Acclimating Fingerlings Before stocking fish in a pond or other rearing area, adjust the water temperature and other water quality fac- tors in the fingerling transport tank to match the pond water. This should be done by gradually transferring small amounts of water from the pond into the hauling tank until the tank water temperature equals that of the pond. Catfish can generally withstand a change of 10 F if the water is tempered over several minutes. For greater temperature differences, one must be very careful to slowly equalize water temperatures before moving fingerlings from the transport tank to the pond. It is best to adjust water temperature about 1 o F every ten minutes. Improper acclimation can directly cause fish to die from temperature shock. If fish are not killed by the shock, they may be weakened and become more susceptible to infectious diseases and parasites. Feeding Catfish grown at high densities require a nutritionally complete feed to maximize growth and maintain good health. Commercially-prepared feeds should contain all essential nutrients and consist of 32-40% protein. Floating pellets or a combination of sinking and floating pellets are desirable in most situations. Fingerlings less than 6 inches should be given pellets smaller than V'/6 inch (Table 3). Fish over V pound can be fed /,6-'/s inch pellets. Food must be stored in cool, dry areas to reduce mold and loss of nutrients that may result from excessive heat. Maximum storage time for feeds is usually 4 to 6 weeks. Food should be distributed at the same locations and at the same time once or twice each day. Do not feed at night, since oxygen requirements of fish increase after feeding and oxygen levels in the water normally decrease at this time. The mid-morning or early afternoon hours are good times to feed. Make sure that food is accessible to all fish by distributing it over broad areas and along upwind shorelines. Do not overfeed since uneaten food can foul the water. Conversely, avoid underfeeding because it can result in poor health, lower growth rates, and greater size variation of harvested fish. Observe feeding activity to make sure that all food is consumed in about 10 to 20 minutes. Recommended feeding allowances for catfish are based on a percentage of the body weight or standing crop weight. Since the conversion efficiency of food is in- fluenced by many factors, such as stocking density, water quality, temperature, and fish size, suggested feeding rates are only approximate guides and the producer must exercise good judgement in establishing a feeding pro- gram. Ideally, fish cultured for food should be fed 1-3%