Mace, Christopher E.

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    Evaluation of ground water from the Lajas valley for low salinity culture of the Pacific white shrimp Litopenaeus vannamei
    (2008-05) Mace, Christopher E.; Kubaryk, John M.; College of Arts and Sciences - Sciences; McGee, Michael V.; Williams, Ernest H.; Pérez Alegría, Luis R.; Aponte, Nilda E.; Department of Marine Sciences; Bunkley-Williams, Lucy
    The ability of the Pacific white shrimp (Litopenaeus vannamei) to acclimate to and survive in low salinity ground water from southwestern Puerto Rico was evaluated using post larval shrimp and well water from the Lajas Valley. Five well sites were selected. Salinity ranged from 0.7-9.8 parts per thousand (ppt). Concentrations of (Na, Cl, K, Ca, Mg, SO4, CO3, and Mn) were determined for each water source. Comparing this with data from results reported in 1991 indicate the deep aquifer (> 45 m) is stable. Eighteen day old post larvae (PL18) were used in 48 h bioassay acclimation experiments. Results were favorable in 2 of 5 well sites with survival ranging from > 99-0%. Survival was highest in low salinity waters (0.7-3.5 ppt). Potassium was deemed deficient in waters with low survival. Adjustment of the Na/K ratio was achieved by addition of potassium rich fertilizer. Two sites (salinities 6.7 and 9.8 ppt respectively) were tested with and without addition of salts (K2SO4 and KCl) to assess the role of Na to K ratios on 48 h survival of post larval shrimp. Survival was assessed in a second 48 h acclimation trial. The two well waters with nothing added served as controls. K levels raised to 3.6% of Na had > 99% survival and the controls had 0-18% survival over 48 h. Results were highly significant (ANOVA, p < 0.001) and were considered positive as the addition of K2SO4 and KCL ameliorated the mortality problems. Subsequently, a recirculating system (1154 L) was constructed to examine long-term survival. Water from well site # 2 (6.7 ppt) was used. The concentration of K to Na was raised to 3.6% by adding K2SO4 and shrimp were acclimated. Nursed juvenile shrimp (30 mm) were stocked into the system at a density of 0.32 shrimp / L. Shrimp lasted over one year in this system, and some grew to over 20 g indicating the feasibility of growing L. vannamei in these low salinity ground waters with proper compensation for low K content.