Live hauling food size channel catfish, Jctalurus punctatus FORREST s. WYNNE1 Food size catfish 0.68-1.36 kg are transported and sold live to processing plants or to live fish markets. Direct sales of catfish to U.S. processors accounted for 94 percent of the large, farm raised catfish in that size range sold in 2004. Recreational, live haulers, retail, government and other uses accounted for the remaining sales (NASS 2005). Catfish sold to processors are delivered by truck and are offloaded into concrete holding vats. Fish are made available from the holding vats to the processing line of the plant as needed. Catfish sold elsewhere are frequently distributed to ethnic, live fish markets, fee fishing operations or stocked into recreational fishing ponds. Some catfish producers transport fish themselves, while others sell their fish to live fish transporters commonly known as live haulers. Often, these fish may be transported for longer distances than those sold to processors. Regardless of where catfish are sold, they should first be taste tested to prevent the sale of off-flavored fish. Feed is withheld from fish 3-5 days, depending on water temperature, prior to harvest. This prevents excessive deterioration of water quality due to the buildup of nitrogenous wastes during transport. Fish are harvested by seining and are graded through one or more mesh live-car or sock device attached to the throat of the seine. After grading, harvestable fish remain in the live car and are dipped out by the seining crew into a loading net. The loading net is attached to a crane scale that is hooked to the cable of a boom truck. When the water is drained out of the loading net fish weight is recorded and the net is positioned over the transport truck's hauling tank. A door is opened in the bottom of the loading net that releases the fish through a top door in the tank. Optimally, catfish are transported in clean, oxygenated well water at a temperature of 1 O-l 6°C. Transport water quality parameters provided by Jensen 1990b are listed in Table 1. Before loading, the weight of fish to be transported must be known in order to determine the water volume Table 1 . Transport water quality parameters for catfish (Jensen 1990b). Dissolved Oxygen >5 mg/L Carbon Dioxide < 20-30 mg/L Total Hardness 50 - 100 mg/L Total Alkalinity 50 -100 mg/L pH 7.0-7.5 Table 2. Transport rates for different sized catfish loaded per kg/L in 18°C water for three trip durations (Piper et al. 1 989).a Number of fish/kg Transport period in hours 8 12 16 2,2046 0.09 0.09 0.09 2,205 0.57 0.45 0.32 1 , 1 02 0.79 0.75 0.57 551 1 .00 0.79 0.68 276 1 .34 1 .00 0.82 1 1 0 1 .56 1 . 13 0.93 8.82 2.27 1 .86 1 .33 4.41 2.68 2. 1 8 1 .56 2.21 2.86 2.52 2. 18 "With every 5.5°C increase in water temperature loading rates must be decreased by 25 percent. Loading rates may be increasedproportionatelyfor similar decreases in water temperature. If transport time exceeds 12 hours the loading rate should be decreased by 25 percent. Loading rates should be decreased by 50 percentfor trips exceeding 16 hours unless transport water is completely exchanged. required for the duration of the trip. One kg of fish displaces approximately 1 L of water inside the hauling tank compartment (Jensen 1990c). Care must be taken not to overload the transport tanks with fish. This decreases the water volume in the tank below the amount required by the fish, which can potentially increase stress and could cause mortality. Live tank loading rates are influenced by many factors, such as the duration of transport, the size and condition of the fish, water temperature and the outside air temperature. Diseased fish should not be harvested or transported inasmuch WORLD AQUACULTURE 41
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