PRODUCING - Alabama Cooperative Extension System

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Figure 18. Estimate the total number of fry by the change in water volume in a graduated wide-mouthed container. mouthed container also graduated in milliliters (Figure 18). When you add all the fry, the water level changes from 500 ml to 900 ml. Then: 300 X (900- 500) Total number of fry=---..:,__----'- 62 -50 300 X 400 or---- 12 10,000 total number of fry FEEDING FRY Begin feeding the fry when they first swim up to the surface with their mouths opening and heads moving back and forth, obviously searching for food. "Swim-up" usually occurs about three to four days after hatching. A high protein diet ( 45 to 50 percent crude protein) with all essential nutrients should be used. Recent findings suggest that the protein should consist of about 60 percent fish meal. The food must be finely ground so the fry can easily consume it. Commercial fry food is usually available. Other suitable feeds such as ground trout feed or salmon starter can be used. Several feeding techniques are practiced. The dry food can be lightly sprinkled on the surface (Figure 19). The fry will eat the portion that floats. The food can also be moistened, formed into a doughball and placed in the fry box or tank. Another technique is to make a slurry and pour it onto a plastic plate anchored to the bottom of the fry box or tank. Feeding activity of fry will keep the feed in suspension where it is easily consumed. Whatever the techniques, the fry should be fed at least six times daily. More frequent feeding is better. Be careful not to overfeed, how- -12- ever, because wasted food will accumulate, causing poor water quality and fungus growth. Waste should be siphoned out and tanks and boxes scrubbed daily. Equipment should be scrubbed and sterilized with a 1:4,000 formalin in water solution after each crop of fry. Water quality in the holding facility determines the length of time the fry can be held in the hatchery. Fry may be held for up to 10 days if good water quality is maintained. Water quality, in turn, is dependent on such factors as water flow rate, number of fry held and cleanliness maintained. Figure 19. Feed • finely ground feed to fry held in boxes. Siphon wastes from boxes and tanks daily. Fry should be eating food before they are transferred into nursery ponds. They survive much better in ponds when stocked as large, strong fry. Growing Fingerlings The pond should be prepared to receive the fry being grown in the hatchery. Pond preparation is critical for good fry survival. Certain aquatic insects and fish eat fry and must be controlled. The "puddle" method of preparing nursery ponds helps control insects and promotes the growth of fish food organisms that fry will eat. Drain and dry ponds thoroughly before stocking the fry. Fertilize with about 100 pounds per acre of old fish food, meat and bone meal or similar organic material just before filling with water. Organic fertilizer promotes growth of zooplankton, tiny aquatic animals that are excellent fry food. Stock the pond on the third or fourth day after the pond begins to fill. With this method, the fry outgrow insects and usually no special insect control
Figure 20. Insects that eat catfish fry (left to right): backswimmer, dragonfly nymph, predaceous diving beetle. Kill back· swimmers and diving beetles with an oil treatment. Drag· onfly nymphs breathe with gills and are controlled by keeping the pond dry until shortly before stocking fry. is required. However, an independent water supply such as a well or spring is needed to fill the pond. CONTROLLING INSECTS Treatment to control insects is necessary when the pond must be filled more than one week before stocking ( Figure 20) . A common practice is to spread a mixture of five to eight gallons of diesel fuel or kerosene mixed with one quart of motor oil per acre over the pond surface two days before stocking. The oil film prevents air-breathing insects from penetrating the surface to breathe. The effectiveness of this treatment depends on complete coverage of the pond surface with oil. Apply oil when there is no wind or just a light breeze. Continue this treatment for the first two weeks at four-day intervals. A disadvantage of this method is that it does not kill gillbreathing insects. It also depresses oxygen levels and inhibits zooplankton growth. STOCKING FRY Stock the fry while it is cool in early morning. Gently transfer them in buckets or similar con- Figure 21. Shelters provide areas for fry to congregate in to aid in feeding and protection. -13- tainers and slowly condition them to the pond by gradually adding small quantities of pond water to the fry container. Shelters such as milk cans or frames covered with black plastic are desirable in the ponds to improve survival and to provide areas for fry to congregate, which aids in feeding (Figure 21). Stocking density depends on the size fingerlings desired at harvest. Growth rate depends primarily on the quantity of food the fry and fingerlings consume if water temperature is optimum. With very high stocking densities, it is unsafe to feed for very long the quantity needed for maximum fish growth, because of water quality problems. Table 4 shows the expected fingerling size for a 120- to 150-day growing season at different stocking densities. V eTy good management is needed to attain these yields. Table 4. EsTIMATED FINGERLING SizE AFTER 120- TO 150- DAY GROWING SEASON AT DIFFERENT STOCKING DENSITIES. Fry stocking density (fish per acre) 10,000 30,000 53,000 73,000 95,000 120,000 140,000 200,000 300,000 500,000 Average length (inches) 7-10 6-8 5-7 4-6 3-5 3-5 3-4 2-3 1-2 1 FEEDING FRY AND SMALL FINGERLINGS Fry and small fingerlings have large appetites and should be fed frequently, two to three times daily for the first two weeks. Feed a finely-ground, 40 percent to 45 percent protein diet the first three to four weeks. Recent studies suggest that the protein should contain at least 20 percent fish meal. Switch to small-size crumbles of more than 40 percent protein from four to six weeks of age and then to a small pellet approximately 3/16 inch in diameter containing 36 percent protein. Make sure that the particle size is small enough to be swallowed by the smallest fish so that the fingerlings grow uniformly. It is better to slightly overfeed in the early stages to ensure that all fry get enough food. As the fingerlings grow, they will eat less food in proportion to their body weight. Feed according to Table 5. However, feeding more than 35 pounds of feed per acre per day will increase the probability of low oxygen problems.
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: Figure 14. Holding boxes should be
Page 15 and 16: Figure 23. Ship diseased fish in a
Page 18 and 19: Table 7. LENGTH AND WEIGHT RELATION
Page 21 and 22: DISEASES Principal Diseases of Farm
Page 23: The -'.1Aiabama W7Cooperative Exten

PRODUCING - Alabama Cooperative Extension System

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