P. G. Lee, C. Zuercher, A. L. Lawrence, P.E. Turk Production losses from disease (i.e. viruses) have had a serious negative economic impact on marine shrimp farming worldwide. The need for specific-pathogen-free (SPF) broodstock that are either geographically or environmentally isolated from common diseases has become a priority. The latter is more difficult to accomplish because of possible sources of contamination from influent sea water, shared facilities and shared personnel. The establishment of commercial, environmentally isolated broodstock also necessitates the use of totally, closed recirculating water filtration systems to contain the costs of water replacement due to declining pH and nitrate accumulation. A commercial biosecure facility composed of 4-100 mt raceway systems has been designed and constructed. The system is composed of 3.3 m W X 33 m L X 1.3 m D concrete raceways housed in greenhouses. Each raceway has a central concrete partition and a 1.6 m deep settling basin at one end. All effluent water is drawn from a screen standpipe located in the middle of the settling basin. Filtered water is returned to the surface of the raceways along the central partition at 1-2 m intervals. In addition, a cleaning system consisting of notched 5 cm polyvinyl chloride (PVC) pipe located along the lateral walls and medial partition suspends uneaten feed and particulates off the bottom. One raceway design has a combination upflow bead (2.2 m^3)/fluidized sand (1.44 m^3) biofilter system supplied with water from 2-l hp pumps (800 1pm). The other raceway design has a reciprocating biofilter (8.9 m^3) supplied by an airlift pump (800 1pm). Both raceways have protein skimmers and activated charcoal filters. Each raceway was designed to produce >100/shrimp m^2 for a total of 40,000 adult broodstock (30-35 g). In addition, the raceways were used to acclimate 5.5 X 10^6 postlarvae before they were stocked into production ponds. In addition, a prototype 5,600 L biosecure broodstock system has been constructed and operated for 26 months. The system is composed of 2-1,900 L shrimp culture tanks, a l m^3 bead filter, a 2.7 m^3 submerged oyster shell biofilter, a protein skimmer, a 0.05 m^3 activated carbon filter, ultraviolet sterilizers and a denitrifying bioreactor. The tanks and filters were sterilized before construction and freshly prepared artificial sea water was used. Two populations of the marine shrimp Penaeus vannamei were reared to adulthood in the system, using a combination of commercial and research pelleted feeds as well as thawed raw squid and bloodworms. Biofilter acclimation was extremely slow because the initial stocking of 200 g of shrimp postlarvae supplied all of the bacteria introduced into the system. As a result, the nitrite peak required over 60 d to disappear and denitrification required a preconditioning period of >150 d. After acclimation, ammonia-nitrogen, nitrite-nitrogen and nitrate-nitrogen concentrations remained below the intended limits, 0.1, 0.05, and 15 ppm, respectively.
(National Resource Center for Cephalopods, Marine Biomedical Institute, University of Texas Medical Branch, Galveston, TX, 77555-1163 USA)