PRODUCING - Alabama Cooperative Extension System

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Table 7. LENGTH AND WEIGHT RELATIONSHIPS FOR VARIous SIZE CHANNEL CATFISH FINGERLINGS. Fish length (inches) 1 2 3 4 5 6 7 8 9 10 Average weight of 1,000 fish (lbs) 0.7 3.5 10 20 32 60 93 112 180 328 Number of fish per pound 1500 286 100 50 31 17 11 9 5.5 3.1 and weighed. The weight of fish per thousand is calculated from the sample. All the fingerlings are weighed as they are loaded into the transporter and the total number is estimated from the average weight of the individual samples. For example, two samples are taken of 200 fish each. Sample weights are 10 ounces and 12 ounces. You then have 22 ounces or 1.4 pounds per 400 fish, or 3.5 pounds per 1,000 fish. The total weight of all the fingerlings divided by 3.5 pounds equals the total number in thousands of fingerlings. From Table 7, the average fingerling length is between three and four inches. Unless the fish are uniformly graded, estimating the average length from the table is unreliable. HAULING Fingerlings may be hauled long distances with proper equipment and care. Use fresh, clean water in the fish transporter. Hauling tanks should be equipped with electric agitators to oxygenate the water and to release waste gases such as carbon dioxide and ammonia. Hauling tanks should not be deeper than 30 inches when only agitators are used. An air blower or bottled oxygen is needed with deeper tanks or with exceptionally heavy fish .loads. Bottled oxygen is also a good backup in case the agitators fail (Figure 29). Bottled oxygen is released into the water through porous diffusers. Small bubbles transfer more oxygen into the water than large bubbles. A combination of small bubbles from bottled oxygen and mechanical agitation achieves high oxygen transfer and good waste gas removal, respectively. The number of fingerlings that can be safely hauled depends mainly on the volume of the transporter, the efficiency of the aeration system, the water temperature, the length of haul, and size and condition of the fish. Hauling tanks should be insulated to prevent water from over-heating, particularly on long trips. Reduce the load given Figure 29. Hauling tanks should always be equipped with bottled oxygen in case other aeration systems fail. Table 8. LoADING RATES FOR TRANSPORTING VARIOus SizE CATFISH Fish size Transport time (hours) (Number per pound) 8 hrs. 12 lm. 16 hrs. - Loading rates (pounds fish/gal) 1 6.3 5.6 4.8 2 5.9 4.8 3.5 4 5.0 4.1 3.0 50 3.5 2.5 2.1 125 3.0 2.2 1.8 250 2.2 1.8 1.5 500 1.8 1.7 1.3 1000 1.3 1.0 0.7 10000 0.2 0.2 0.2 Rates given are for water temperature at 65°F and assume proper equipment and aeration. Reduce rates by 25 percent for each 10°F rise in temperature. -18-
Figure 23. Ship diseased fish in a plutic bag with oxygen and water packed in a styrofoam container with ice to ensure survival. The laboratory will infonn you of the diagnosis and recommend a treatment if needed. Chemical treatments are generally a last resort and are recommended when there is no alternative. Table 3 contains chemical treatment recommendations for common fish diseases. Take every precaution when applying chemicals. Fish have narrow tolerance ranges for some chemicals, so very exact calculations are needed. Determine and record the volume of all your ponds, tanks and troughs for reference. Calculating treatment rates is much faster when this information is readily available. Some characteristics of the water may affect the treatment rates. Analyze your water before you treat. Copper sulfate, for example, is toxic to catfish in very soft water. When the water has less than 20 ppm total alkalinity, do not use copper sulfate before consulting with a fisheries biologist. Use a treatment rate of 0.5 ppm when total alkalinity is between 20 and 50 ppm. Higher treatment rates are needed in more alkaline water. Use 1.0 ppm copper sulfate when alkalinity is between 50 and 100 ppm and 1.5 ppm copper sulfate when alkalinity is between 100 and 150 ppm. Water of 150 to 200 ppm alkalinity needs 2 ppm copper sulfate. Copper sulfate is ineffective in water of alkalinity greater than 200 ppm. Potassium permanganate is commonly recommended for treating some external bacterial and parasitic diseases. It is an oxidizing agent that reacts with organic matter in pond water. The portion of chemical that reacts with organic matter is ineffective in controlling disease. As a rule of thumb, apply the recommended rate of potassium permanganate and watch for the water to change color. If the water turns -15- brown within 12 hours after treating, the full rate must be applied again. Ichthyopthirius, commonly called "Ich," is probably the biggest killer of fingerling catfish. "Ich" is a tiny parasite that burrows into the fish's skin and gills, causing white, pin-head-sized spots which can easily be seen. This disease is most common in the spring when water temperature is between 68°F and 77°F; however, it can appear at any time of year. Treat "Ich" using 25 ppm formalin ( 37 percent formaldehyde) every three days when the water temperature is between 60° F and 70°F, every seven days when the temperature is between 50°F and 60°F and every 14 to 21 days when the temperature is below 50°F. Chemicals used for treating diseases should be thoroughly mixed and evenly distributed from a boat. Always wear protective clothing and follow label instructions carefully. Potassium permanganate, formalin and copper sulfate kill algae in ponds, which may cause low oxygen problems. Be sure to have emergency aeration equipment readily available when treating with these chemicals. Channel catfish virus disease ( CCVD) is a disease that affects only fry and fingerling channel catfish when the water is warmer than 70°F. Signs of this disease are pop-eye, hemorrhaging at the base of the fins, swollen belly and pale gills. Behavior includes erratic swimming and :floating head-up. There is no cure for this disease, so prevention is essential. Isolation of infected brood stock is important because exposed adults are believed to be carriers. WATER QUALITY Good water quality is essential to producing healthy fingerlings. Low oxygen is by far the most common water quality problem. Oxygen levels should be above four ppm at all times for fingerlings to grow well. Growth can be severely slowed when oxygen remains below three ppm for long periods. Stress caused by these conditions can also lower resistance to disease. Algae, the tiny plants that give water a green color, produce oxygen during bright daylight and put it into the water. However, no oxygen is produced at night, and respiration of fish, algae and decaying wastes take oxygen from the water. When temperatures are high and fish are growing rapidly, more oxygen may be taken out at night than is being produced during the day. Also; cloudy days may reduce the amount of oxygen produced. The result can be dead fish. The probability of low oxygen levels increases with higher
Page 1: CIRCULAR ANR-327 PRODUCING Channel
Page 4 and 5: producers select the best brood fis
Page 6 and 7: Figure 5. Eggs are laid in a jelly-
Page 8 and 9: Figure I. Treat egg ma•M• gentl
Page 11 and 12: Figure 14. Holding boxes should be
Page 13 and 14: Figure 20. Insects that eat catfish
Page 15 and 16: Figure 23. Ship diseased fish in a
Page 21 and 22: DISEASES Principal Diseases of Farm
Page 23: The -'.1Aiabama W7Cooperative Exten

PRODUCING - Alabama Cooperative Extension System

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