A diet of newly hatched Artemia (five nauplii/L/day) and dry postlarval feed (50% protein) is fed at 10 to 25 percent of the total body weight per day (bw/d) for the first 5 days after stocking. Then the feed rate is reduced to 7.5 percent bw/d and the feed is changed to a 40% protein crumble #0 feed.
The crumble size is gradually increased (0, 1, 2, 3 and 4) as the shrimp grow. Shrimp feed is provided at 7.5 percent bw/d for days 6 through 14, then reduced to 6 percent bw/d for the remainder of the culture period.
Nursery growth rate:
Under intensive nursery culture, native shrimp have grown from a PL10to 0.5 g in 50 to 60 days. Supplemental oxygen and periodic filtration (using a sand or bead filter) are necessary to complete the nursery cycle as the biomass increases to more than 2.5 kg/m2.
Nursery harvesting:
Nurseries should be equipped with a harvest basin and constructed to drain fully. Harvest begins in the early morning when the nursery is drain-harvested into a harvest basin. Shrimp are removed from the harvest basin with collection nets and transferred to hanging balances for group weights. During the weighing process, a periodic sub-sample of the population is weighed and counted to determine the average weight of the population.
The average weight and total biomass are used to determine total shrimp harvested and the survival in the raceways Total shrimp harvested = Total biomass weighed ÷ Average weight Survival rate = (Total shrimp harvested ÷ Number of shrimp stocked) x 100 % The shrimp are rapidly weighed and placed in hauling tanks equipped with oxygen injection for transportation to the pond.
Intensive pond production:
For optimum production, pond water should have a temperature of 28 to 29 °C (82.4 to 84.2 °F), a salinity of 20 to 30 ppt, a dissolved oxygen level higher than 5 mg/L, a pH higher than 7.5, and a Secchi depth of 25 to 30 cm. Ponds may be disinfected with 10 ppm chlorine upon filling to kill viral vectors and pathogens that may be introduced from wild sources.
However, this may not be economically feasible, given the cost of chlorine and size of the operation. Whether or not a pond is dechlorinated, incoming water should always be filtered with 200-micron socks.
Ponds are filled and fertilized with 200 pounds per acre of cottonseed meal 5 to 7 days before stocking. Culture water from an established pond is transferred into the new pond to inoculate it and expedite the algal bloom. The algal bloom should be well established (25 to 30 cm Secchi depth) when shrimp are stocked.
Once in the ponds, shrimp are fed a 30 to 35% protein feed at rates of 3 to 6 percent bw/d. Feed trays are used to prevent overfeeding. The water must be aerated at a rate of 10 to 18 hp per acre . The general pond culture period for 90-count shrimp (5.0 g) is 90 days.
Ponds stocked with 0.5-g shrimp at a density of 200 per m2 can grow at a rate of 0.5 g per week, have 70 percent survival, and produce up to 7,000 kg/ha (6,160 lbs/ac) of market size (5.0-g) live bait shrimp.
Pond harvesting:
Shrimp are harvested in the early morning when the temperature is low. A seine can be used to manually harvest the pond, though this method is labor intensive. Another method uses a hydraulic fish pump attached to the harvest basin to drain-harvest the pond.
Harvested shrimp are rapidly weighed in small batches (less than 35 pounds each) before being loaded into a hauling truck. The hauling truck is equipped with oxygen injection to maintain saturated oxygen conditions (more than 10 mg/L) during transport.
The temperature is also lowered to about 20 °C (68 °F) to reduce stress. Farmers who harvest and sell live shrimp to wholesalers at pond bank can expect prices of $4.50 to $5.50 per pound. Farmers who invest in hauling trucks and equipment can expect to receive more than $7.50 per pound for delivered shrimp.
Other culture systems:
Since the mid 1990s, researchers have been developing super-intensive, closed-recirculating shrimp production systems. Recent advances in this technology have made it possible to produce shrimp year round under high density conditions (3 to 7 kg/m2). These systems are still in the research and development phase so capital and operating costs are much higher (more than $3.50 per pound) than with pond production methods ($1.25 to $2.50 per pound).
The economic feasibility of these production systems is currently limited to markets where prices are consistently high (more than $5.00 per pound). Superintensive production systems are marginally profitable when the price falls below $5.00 per pound.
These systems are not economically feasible when there is considerable competition or profit margins are low, but they do show promise for year-round production or for facilities that must be located inland in biosecure areas.
Author:
Ryan L. Gandy
