14 JUNE 2014 • WORLD AQUACULTURE • WWW.WAS.ORG The Clemson PAS With help from faculty, students, and staff at Clemson, including John Collier, Tom Schwedler and Arnie Eversole, we built four, 100-m2 PAS prototypes (Fig. 3). During the first years of operation we focused only on growing algae in the system, simulating fish metabolic nitrogen production by adding ammonia fertilizer. During this time, we determined optimum operating water depth, paddlewheel speed, and potential fish carrying capacity (Drapcho and Brune 2000). By the early 1990s, Tom Schwedler, the fish culturist at Clemson, had become convinced of the fish production potential of the PAS. At that point, we designed, installed, and began operation of the first fully operational PAS units for channel catfish production. These prototypes consisted of six, 0.13-ha units (Fig. 4). We later built a 0.8ha unit using a slightly different design (Figs. 5, 6 and 7). Over 7 years, we systematically increased annual production to 20 t/ha of channel catfish with coproduction of 5 t/ha of Nile tilapia. The costs of producing channel catfish in the PAS were comparable to those for conventional pond culture (Goode et al. 2002). In 2000, we installed a greenhouse-covered version of the PAS at Clemson dedicated to penaeid shrimp aquaculture and produced 12 to 35 t/ha of Pacific white shrimp Litopeneaus vannamei (Fig. 8; Brune et al. 2012). From 2005 through 2009, we also produced 5.2 t/ha of large (110 g) catfish fingerlings in single summer seasons in net-pens contained in the 0.8-ha PAS unit (Wells 2009). Clemson University was granted a United States patent for the PAS (Brune et al. 2001). Recent PAS Developments During my years at Clemson, I also worked with Kent Bioenergy, in southern California, looking at ways to take advantage of and add value to the high rate of algal biomass production in the PAS. We examined the possibility of converting algal biomass into a variety of higher-value products, from biofuels to pharmaceuticals (Brune and Beecher 2009; Brune et al. 2012). For the last 3 years, I have been operating a zerodischarge marine shrimp culture system at the University of Missouri (Fig. 9). The system is based on the original PAS design, using both tilapia and brine shrimp coculture to harvest and convert excess algal and bacterial biomass into higher-value co-products, including fish food, fishmeal replacement, biofuels and bioenergy products. This approach could potentially reduce the fossil-fuel requirement of fed fish and shrimp production. These systems can produce marine shrimp at costs competitive with Asian semi-intensive shrimp production, with no water discharge, while replacing 30 to 100 percent of the feed required in conventional fish or shrimp culture with TOP, FIGURE 7. Aerial photograph of Clemson University partitioned aquaculture systems. Six, 0.13-ha units are located at the bottom of the photo and a single 0.8-ha unit is at the top. The design of the larger unit is shown in Figures 5 and 6. MIDDLE, FIGURE 8. Greenhouse-covered PAS culture of marine shrimp at Clemson University, 20012009. BOTTOM, FIGURE 9. Greenhouse-covered 200-m2 PAS units at University of Missouri (2010-2014) for co-culture of marine shrimp, brine shrimp and tilapia.
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