Broodfish and hatchery management

Proper management and care of broodfish are critical for high reproductive or spawning success. Many factors such as water quality, stocking density, and management outside the spawning season can affect catfish reproduction. Spawning success can be as high as 20 to 30% in two-year-old fish, but best reproduction is obtained from three- and four-year-old fish. The industry average for spawning success is estimated to be around 30 to 40%, and for egg hatching around 60%. A sex ratio of 1:1 or 2:1 females to males is desirable and should be closely monitored each year, because males have higher mortality rates than females. Male and female catfish are sexually dimorphic. Males typically are darker in color and have larger heads, whereas females are lighter in color and typically have swollen abdomens during the spawning season, because of ovary development. Broodfish should be stocked at no more than 1200 pounds per acre into ponds that have been drained, allowed to dry, and recently reflooded. After the spawning season, broodfish can be moved and restocked into ponds at 3000 to 4000 pounds per acre. Broodfish should be fed a nutritionally complete floating commercial diet, with at least 28% protein, at 2% of body weight per day when water temperatures are above 700F, and at 1% per day with a slow-sinking pellet at temperatures between 550 and 700F. Generally, no feed is offered below 500F.

Spawning activity will begin in the spring when water temperatures are consistently around 75OF. Maintaining optimum water quality in spawning ponds is important, because low levels of dissolved oxygen and excessive algae and aquatic weed growth will inhibit spawning success. Commercial farmers place 50 to 75 spawning cans into ponds for each 500 females. Spawning cans can be checked every two days during the spawning season. Eggs should not be crowded into transport containers and transport water should not become warmer than 85 OF before transport to the hatchery.

Well water with temperatures between 75OF and 820F is preferred for hatching catfish eggs. Eggs are usually incubated in long, shallow troughs or tanks with aeration paddles or diffused aeration (Fig. 3). Dissolved oxygen levels should be maintained above 6.0 ppm, total water hardness and alkalinity at >20 ppm, pH between 7.5 and 8.5, and total gas pressure at 100% of saturation, or less. Maintaining optimum water temperatures, cleaning hatchery equipment, and using formalin and iodophores will minimize bacterial and fungal infections on eggs. Eggs hatch in five to seven days after spawning, and fry will actively start swimming and begin feeding three to four

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Fig. 2 Aerial view of levee ponds used for channel catfish culture. (View this art in color at www.dekker.com.)

Fig. 3 Catfish eggs being incubated in a hatching trough. (View this art in color at www.dekker.com.)

days after hatching. Fry must be fed a high-protein diet (usually 45% protein) at least 12 to 24 times per day.

Fingerling culture

Growth and survival of catfish fry to fingerling size depend on maintaining water quality, controlling disease, and providing enough feed to achieve the desired harvest size. Although the industry average for survival of fry to fingerling has been estimated at 65%, with a yield of about

3000 pounds per acre, acute problems with disease and water quality can drastically affect survival and yield in fingerling ponds. Fry/fingerling ponds should be drained and dried to kill all trash fish and vegetation before filling with well water. Ponds must be fertilized, checked for zooplankton populations, and have predaceous insects controlled, following recommended management guidelines. Fry can be counted volumetrically or by weight prior to stocking into ponds, and should be stocked at 7 to 10 days old, after they are actively feeding. Fry are normally stocked at a rate of 75,000 to 125,000 fry per

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Fig. 4 Catfish are harvested from ponds using tractors to pull large seines. (View this art in color at www.dekker.com.)

acre. Morning dissolved oxygen readings should be above 5 ppm, and stocking should be completed before water temperatures exceed 85°F. Vaccination of fry against bacterial diseases may improve survival.

After stocking, catfish fry should be fed finely ground feed (usually 40 to 50% protein) two to three times daily (20 to 30 lbs/acre/day) until fish are observed feeding and swimming on the pond surface. Fry should be observed feeding on the surface within three to five weeks after stocking. At this time, a small-pellet floating feed can be fed to satiation daily, once the fish are actively feeding. Supplemental aeration is necessary for fingerling ponds, and addition of salt to maintain chloride levels of 100 ppm is often recommended. At the onset of cool weather in the fall, when morning pondwater temperatures begin to drop below 80°F, fish can be placed on a restricted feeding regime on alternate days, or every second day. Feed containing antibiotics (Romet® or Terramycin®) is often used if juvenile or fingerling fish are diagnosed with bacterial infections and a diagnostic laboratory has recommended treatment.

Foodfish culture

No single, well-defined production schedule is used on commercial farms because food-size fish are harvested and fingerlings are stocked year-round. Management practices for stocking density, sizes, feeding practices, and water-quality management are often specific to individual farms. Fingerlings are typically stocked into growout ponds at 5000 to 8000 fish per acre, and rates of up to 10,000 fish per acre are not uncommon. Maintaining optimum water quality is critical for high production levels and profitability. Most production ponds are monitored daily for water quality parameters and have electrical aeration to maintain dissolved oxygen levels. Chloride levels should be maintained around 100 ppm to prevent nitrite toxicosis and enhance osmoregulation. Industry average mortality is estimated to be 2% per month. Fingerlings typically reach marketable size in 150 to 300 days. Catfish are harvested from ponds using large seines pulled by tractors (Fig. 4), and then are transported alive to processing plants.

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