Bait Shrimp Culture

SRAC Publication No. 1201 VI April 2007 PR Bait Shrimp Culture Ryan L. Gandy1 The live bait shrimp industry in pound. This wholesale price However, live-haul trials of farm- the southeastern U.S. is dependent includes delivery from the shrimp raised, live bait shrimp showed on three shrimp species: the boat to the retail bait shop and so that commercial volumes (200 to Atlantic white shrimp (Litopenaeus it varies with the distances 500 pounds per shipment) could setiferus), the Gulf brown shrimp involved. Retailers who own their be successfully transported to (Farfantepenaeus aztecus) and the own shrimp boats may charge fish- retail bait shops with more than Gulf pink shrimp (F. duorarum). ermen as little as $7.00 per pound; 95 percent survival 24 hours after All three species occur along the in general, fishermen pay $10 to delivery. southern and eastern U.S. coasts $16 per pound for live bait shrimp from Texas through North (Fig. 1). Seed supply Carolina. The live bait shrimp The main impediment to bait industry within this extensive Live hauling bait shrimp shrimp aquaculture has been the coastal region is mostly a capture Wild-caught bait shrimp are trans- lack of consistent supplies of dis- fishery. Juvenile shrimp within a ported to market in oxygenated ease-free postlarvae (PL). Without size range of 150- to 60-count holding tanks at densities of 1 to them, both researchers and com- shrimp (3.0- to 7.5-g) are harvested 2 pounds per gallon of water. mercial aquaculturists have relied from inshore waters with trawling Mortality rates can be 25 to 50 per- on two methods of obtaining PL. gear. Recently, farm-raised, live cent within 24 hours of delivery. bait shrimp were introduced as an alternative to wild-caught shrimp. Bait shrimp market The wild product is highly season- al and the supply rarely meets demand, especially during the peak demand period of March through September. Shrimp are sold as both a live and a frozen product, with live shrimp commanding a premium price. The dockside (ex-vessel) price wholesalers pay to boat captains for live bait shrimp ranges from $2.75 to $4.00 per pound. The wholesale price bait retailers pay ranges from $7.50 to $14.00 per 1 Mote Marine Laboratory Shrimp Research Program, Sarasota, Florida. Figure 1. The most valuable consumers of live bait shrimp. Method I - sourcing wild, mated, these populations. Once a “high- plied with a combination of fresh gravid females health” wild population has been squid, adult enriched Artemia and isolated, it is induced to spawn bloodworms fed on a wet-weight This method entails leasing coastal and its offspring are tested for basis (20 percent of body weight shrimp boats during the full moons known viral pathogens. Once the per day, bw/d). Dry maturation of spring and early summer to offspring are determined to be diets are added to reduce the cost trawl the spawning grounds for “clean,” they are moved to a biose- of fresh food. mated, gravid (egg-bearing) females cure grow-out facility where they Once acclimated to the maturation (Fig. 2). Once gravid females are are raised to broodstock size. The caught, they are either spawned in system, females are unilaterally broodstock are then reproduced in ablated—a process in which one individual tanks onboard the vessel maturation facilities and their off- or transported to land-based eyestalk is removed to induce mat- spring are used to supply farmers uration. Ovarian development spawning tanks. Each gravid with PL. female is kept in an individual tank ensues within 72 hours and mating for 12 to 36 hours under dark con- The maturation and reproduction and spawning begin thereafter. ditions, at a temperature of about of broodstock occur in a climate- Broodstock ranging from 25 to 35 g 28 °C (82.4 °F), and at a salinity of controlled maturation system have a reproductive capacity of 30 to 35 ppt. After spawning, the (27 °C, 80.6 °F) with 14-hour light 100,000 to 250,000 eggs per spawn female is removed from the tank and 10-hour dark photoperiods and can spawn every 3 to 7 days. and the fertilized eggs hatch within (Fig. 3). Broodstock are kept in Fertilized eggs will hatch within 24 2 24 hours. 10.5- to 16.4-m (12-ft to 15-ft hours of fertilization at 28 °C diameter) maturation tanks at den- (82.4 °F). The nauplii are allowed Sourcing wild, mated, gravid 2 sities of six shrimp per m . During to remain in hatching tanks until females is a cost-effective tech- maturation, broodstock are sup- nique for acquiring fertilized eggs, they metamorphose into the last but it is not a reliable year-round production method. There also is a high risk of acquiring shrimp infected with viral pathogens that will jeopardize the biosecurity and sustainability of the farm. Method II– hatchery Developing and operating a biose- cure hatchery is both capital and labor intensive. However, a biose- cure hatchery ensures a sufficient year-round supply of PL for commercial operations. Healthy broodstock must be developed and maintained in a disease-free hatchery. The quantity of viral pathogen-free broodstock is limited. Researchers at the Mote Marine Laboratory in Sarasota, Florida, the Waddell Figure 2. Sourcing gravid females at night onboard a shrimp boat. Mariculture Center in Bluffton, South Carolina, and the Texas Agricultural Experiment Station in Corpus Christi, Texas, are isolating and developing “high-health” broodstock populations of the Atlantic white shrimp and Gulf pink shrimp. “High-health” broodstock are developed through a process of quaran- tine and routine population testing using histological examination and a polymerase chain reaction (PCR) technique. Continuous screening of broodstock and offspring with these diagnostic tools detects organisms with specific pathogens so they can be eliminated from Figure 3. Maturation system. naupliar stage (N5). During the As a general rule, the acclimation farmers may increase production naupliar stages, no feed is provided temperature is changed by 1 °C densities to more than 2.5 kg/m2. as nauplii feed on their yolk sacs. (1.8 °F) every 15 minutes until it Intensive nurseries increase grow- Nauplii (N5) are then collected and matches the culture system tem- out survival by allowing farmers to transferred to larval-rearing tanks perature. Once temperature is stock larger shrimp (0.25 to 1.0 g) maintained at 28 to 29 °C (82.4 to adjusted, salinity can be changed into grow-out systems. In the tem- 84.2 °F) where they are fed marine by 1 ppt every 15 minutes until it perate climate of the southeastern algae (Chaetoceros gracilis and matches the culture tank salinity. U.S., greenhouse-enclosed nurs- Isochrysis galbana), live, newly If the pond has less than 15 ppt eries are used to give shrimp a hatched Artemia nauplii, and dry salinity and/or a temperature of head start in early fall (Fig. 4). A larval and postlarval diets, depend- less than 20 °C (68 °F), it is “head start” nursery is an effective ing on the stage of development advisable to use a nursery phase way to increase the number of and the dietary needs of that stage. and stock older, heartier juveniles crops each year and have better Shrimp larvae go through six larval later on. control over production by stock- stages over a 9-day period in the Zero exchange ing known quantities of heartier larval-rearing tank before they juveniles. In regions where early metamorphose to a postlarval (PL1) intensive nurseries spring temperatures are cooler stage. The entire larval cycle from Intensive nurseries (1,000 to than 20 °C (68 °F), greenhouse 2 nurseries are essential so that the N5 until the shipment of the PL8-13 50,000 PL/m ) with biomass lasts 17 to 22 days, depending on capacities of 2 to 4 kg/m2 operated crop can be held until water in the the age of the PL requested by the under zero exchange have become grow-out system warms up. farm. In general, farmers request an important tool for shrimp Nursery management PL8 - PL13 for stocking production farmers. Zero exchange nursery systems. systems can have survivals of Nursery culture water is main- more than 80 percent and a har- tained at a temperature of 28 to Shipping post-larvae vest biomass of 1 to 7 kg/m2, 29 °C (82.4 to 84.2 °F), a dissolved Post-larvae are removed from lar- depending on the skill of the oxygen level of 5 to 7 mg/L, a pH val-rearing tanks and concentrated management and the investment of 7.5 to 8.5, and a Secchi depth of for counting, packing and ship- in capital infrastructure (filters 25 to 30 cm. Ten to 14 days before ping. Shrimp PL are shipped at and oxygenation). Basic systems PL arrive from a hatchery, the cul- densities of 1,000 to 2,000 per L in consist of a green house enclo- ture tanks are filled with seawater polyethylene bags containing sea- sure; a 20- to 60-mil, high-density, (20 to 35 ppt). Then the water is water (30 to 35 ppt) that is saturat- polyethylene (HDPE) liner; a sand sterilized with sodium hypochlo- ed with oxygen and cooled to or bead filter; a regenerative rite (household bleach at 10 ppm) 18 °C (64.4 °F) before packing. blower for aeration; a propane or to prevent the introduction of The bags are usually packed in electric heat source; and oxygen pathogens from incoming waters. insulated foam coolers to maintain injection for large biomasses The treated culture water is temperature during shipping.

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