FAMILY: Penaeidae and Palaeomonidae
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NAME: Penaeus setiferus, monodon, japonicus, stylirostris, vannamei, Macrobrachium rosenbergii - Shrimp and prawns |
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Data provided courtesy of Aquaculture/Fisheries Center, University of Arkansas at Pine Bluff - (Dr. Peter Perschbacher) |
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DISTRIBUTION:
This family of decapods has a cosmopolitan distribution. HABITS: The marine penaeids generally inhabit the littoral zone and exhibit seasonal and diurnal migrations during the year. Penaeus japonicus are almost exclusively found on sandy bottoms while some of the others prefer turbid waters. Macrobrachuim postlarvae, once classified as Penaeus, can tolerate a range of salinities and migrate to freshwater upon transformation. In addition to the food they ate as larvae, larger pieces of animal and plant materials will be ingested. The diet includes larval and adult insects, algae, mollusks, worms, fish, and feces of fish and other animals. At high densities, or under conditions of food limitations, prawns become cannibalistic. SPAWNING: For Macrobrachuim males generally become reproductively mature within 6 months. Mating can occur only between hard-shelled males and soft-shelled females, i.e., females who have just completed a premating or prenuptial molt. The male deposits sperm into a gelatinous mass that is held underneath the body of the female, between her fourth pair of walking legs. Eggs are laid within a few hours after mating and are fertilized by the sperm contained in the gelatinous mass attached to the outside of the female's body. The female then transfers the fertilized eggs to the underside of the abdominal (tail) region, in a "brood chamber," where they are kept aerated and cleaned by movement of the abdominal swimming appendages. Eggs remain attached to the abdomen until they hatch. The number of eggs produced at each spawn is directly proportional to the size of the female. As long as water temperature exceeds 70 °F, multiple spawns per female can occur annually. Females carrying eggs are termed "berried females." The bright-orange color of newly spawned eggs gradually changes to orange, then brown, and finally gray about 2 to 3 days before hatching. At a temperature of 82 °F, the eggs hatch approximately 20 to 21 after spawning. Newly hatched freshwater prawns enter into a larval phase of growth and metamorphosis. After hatching, larvae are released and swim upside down and tail first. The larvae cannot survive in freshwater beyond approximately 48 hours and migrate to brackish water with a salinity of 10 to 14 parts per thousand (ppt). Larvae are aggressive sight feeders and feed almost continuously, primarily on small zooplankton, worms, and larval stages of other aquatic invertebrates. Larvae undergo 11 molts, each representing a different stage of metamorphosis. Following the last molt, larvae transform into postlarvae. Transformation from newly hatched larvae to postlarvae requires 15 to 40 days, depending upon food quantity and quality, temperature, and a variety of other water quality variables. Penaeus species spawn off shore where eggs are released into the open ocean. They hatch within 18-24 hours at 28C. Unlike the fresh water prawns there are 5 naupliar stages, 5 proozoea stages, and 3 mysis stages. Other wise they are rather similar. GROWTH: P. monodon is one of the largest and fastest growing fish species. Grow-out take about 4-6 months for these animals to reach 20-30g. These shrimp have been raised to 30g in 120 days in the Philippines. P. japonicus reach market size of 20g in 5 to 6 months. USES: These shrimp and prawns are almost exclusively raised for the seafood market. A small portion, usually the culls, are sold as bait to anglers. CULTURE: There are three phases of culture of the freshwater prawn -- hatchery, nursery, and pond grow out. If you are contemplating starting a freshwater shrimp production enterprise, forego, initially at least, the hatchery phase and possibly the nursery phase by purchasing juveniles from a supplier. As production increases and you are successful at pond grow out of the animals, you should begin plans to develop a nursery, and possibly a hatchery. There are a limited number of juvenile prawn suppliers, but increased demands will eventually lead to a need for more enterprises that deal exclusively in the production and sale of seed stock. Ponds used for raising freshwater prawns should have many of the same basic features of ponds used for the culture of channel catfish. A good supply of fresh water is important, and the soil must have excellent water-retention qualities. Well water of acceptable quality is the preferred water source for raising freshwater prawns. Runoff from rivers, streams, and reservoirs can be used, but quality and quantity can be highly variable and subject to uncontrollable change. The quality of the water source should be evaluated before any site is selected. Locate ponds in areas that are not subject to periodic flooding. Before building ponds specifically for producing freshwater prawns, check the soil for the presence of pesticides. Prawns are sensitive to many of the pesticides used on row crops. Also, analyze the soil for the presence of residual pesticides. Do not use ponds that are subject to drift from agricultural sprays or to runoff water that might contain pesticides. The surface area of grow-out ponds ideally should range from 1 to 5 acres. Larger ponds have been successfully used; ideally the pond should have a rectangular shape to facilitate distribution of feed across the entire surface area. The bottom of the pond should be completely smooth and free of any potential obstructions of seining. Ponds should have a minimum depth of 2 feet at the shallow end and a maximum depth of 3.5 to 5 feet at the deep end. The slope of the bottom should allow for rapid draining. You can obtain assistance in designing and laying out ponds by contacting a local office of the Natural Resources Conservation Service (formerly Soil Conservation Service). Collect a soil sample from the pond bottom to determine whether lime is needed. Take soil samples from about six different places in each area of the pond, and mix them together to make a composite sample that is then air-dried and analyzed. If the pH of the soil is less than 6.5, agricultural limestone must be added to increase the pH to a minimum of 6.5, and preferably 6.8. After filling the pond, fertilize the pond to provide an abundance of natural food organisms for the prawns and to shade out unwanted aquatic weeds. A liquid fertilizer, either a 10-34-0 or 13-38-0, gives the best results. Apply 1/2 to 1 gallon of 10-34-0 or 13-38-0 liquid fertilizer per surface acre to the pond at least 1 to 2 weeks before stocking juvenile prawns. If a phytoplankton bloom has not developed within a week, a second application of the liquid fertilizer is used. Usually it is sprayed from the bank or applied from a boat outfitted for chemical application. At least 1 or 2 days before stocking the juvenile prawns, check the pond for aquatic insect adults and larvae that might eat the juvenile prawns. You can control the insects by using a 2:1 mixture of motor oil and diesel fuel at the rate of 1 to 2 gallons per surface acre on a calm day. The oil film on the water kills the air-breathing insects and is more effective when applied on calm days. If a water source other than well water is used, it is critically important to prevent fish, particularly members of the sunfish family (e.g., bass, bluegills, and green sunfish) from getting into the pond when it is filled. The effects of predation on freshwater prawns by these kinds of fish can be devastating. If there are fish in the pond, remove them before stocking prawns, using 1 quart of 5 percent liquid emulsifiable rotenone per acre-foot of water. Juvenile prawns stocked into grow-out ponds initially are able to obtain sufficient nutrition from natural pond organisms. At the recommended stocking densities, begin feeding when the average weight of the prawn is 5.0 g or greater. Commercially available sinking channel catfish feed (28 to 32 percent crude protein) is an effective feed at the recommended stocking densities. The feeding rate is based upon the mean weight of the population (Table 1). A feeding schedule has been developed by researchers at the Mississippi Agriculture and Forestry Experiment Station and is based upon three factors: A feed conversion ratio of 2.5; one percent mortality in the population per week; and mean individual weight determined from samples obtained every 3 weeks. At the end of the grow-out season, survival may range from 60 to 85 percent. Many of the above recommendations hold true for salt water culture of peneids. These ponds are usually located in hard to reach areas though. Many do not have road access such as those in Honduras and Columbia. Also water quality is of great issue and common discharge from the ocean and recharge with fresh seawater is common. Sinking pelleted feeds are used as these organisms feed benthically in the shallow ponds. High feeding rates are used but above 100-150 kg/ha causes great water quality deterioration. REFERENCES:
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