Effects of Artificial Substrate and Water Source on Growth of Juvenile Pacific White Shrimp, Litopenaeus vannamei CLETE A. OTOSHI 1 ,ANTHONY D. MONTGOMERY ,ERIC M. MATSUDA, AND SHAUN M. MOSS Oceanic Institute, 41-202 Kalanianaole Highway, Waimanalo, Hawaii 96795 USA Commercial shrimp farmers must continually assess strategies to reduce operating costs and increase production in an effort to maximize profitability. One common approach is to pro- mote natural productivity in the culture system to provide supplemental food resources for the target species. Anderson et al. (1987) reported that 53–77% of the growth of juvenile Pacific white shrimp, Litopenaeus vannamei, raised in earthen ponds was because of the assimilation of in situ natural pond biota. Epp et al. (2002) estimated that as much as 31% of the nitrogen requirements of L. vannamei were obtained from natural production. Bianchi et al. (1990) reported that 70–80% of the weight gain of L. vannamei reared under laboratory conditions was attributed to the consumption of bacterial floc. Additionally, several studies conducted at the Oceanic Institute (OI, Waimanalo, HI, USA) have shown that growth rates of juvenile L. van- namei reared under intensive culture conditions were significantly enhanced when shrimp were grown in organically rich pond water versus clear well water (Leber and Pruder 1988; Moss et al. 1992; Moss 1995; Divakaran and Moss 2004). In addition to promoting natural productivity, shrimp farmers and researchers have used artifi- cial substrate to increase production. Artificial substrate can provide additional surface area upon which shrimp graze attached biota and can serve as a refuge for shrimp. However, research results on the benefits of artificial sub- strate have been conflicting. Sandifer et al. (1987) reported that artificial substrate, in the form of fiberglass screens, enhanced shrimp survival but did not increase growth rates of nursery-sized L. vannamei. Samocha et al. (1993) reported that the addition of vertical net- ting did not improve survival, growth, or feed conversion ratio (FCR) of L. vannamei reared under intensive culture conditions. More recently, Bratvold and Browdy (2001) reported that shrimp weight, survival, and production were significantly enhanced in the presence of the artificial substrate AquaMats TM during the grow-out phase of production. Similarly, Moss and Moss (2004) reported that growth rate was significantly greater and FCR was signifi- cantly lower in the presence of AquaMats than without the added substrate during the nursery production of L. vannamei. The objective of this study was to investigate how natural pro- ductivity and artificial substrate affect growth and survival of juvenile L. vannamei. In addi- tion, this study was conducted to assess the relative importance of nonnutritional benefits associated with artificial substrate, such as pro- viding refuge for the shrimp. Materials and Methods This experiment was conducted in an indoor laboratory located at OI. Twelve 110-L cylindri- cal plastic tanks were stocked with 2.29-g (SD 6 0.02 g) Pacific white shrimp, L. vannamei, at a density of 22 shrimp per tank (79 shrimp/m 2 equivalent). Shrimp were free of specific patho- gens listed by the U.S. Marine Shrimp Farming Program (2003), including those pathogens that are OIE (International Office of Epizootics) noti- fiable (OIE 2002). Tanks received flow-through water that was supplied to the tanks at a rate of 0.8–1.1 L/min, and the water came from one of two sources: (1) clear well water pumped from a seawater aquifer or (2) water pumped from OI’s 337-m 2 round pond used for intensive shrimp culture. Well water was the source water for the round pond, so any differences in water 1 Corresponding author. JOURNAL OF THE WORLD AQUACULTURE SOCIETY Vol. 37, No. 2 June, 2006 Ó Copyright by the World Aquaculture Society 2006 210