Inland marine shrimp (L.vannamei ) production popularity is increasing as recirculating aquaculture systems (RAS) can provide a fresh, high-valued product year-round to nearby consumer markets. If operated in a controlled environment, high animal stocking densities and limited water exchange make RAS an attractive option, minimizing space and water requirements. A complete, artificial sea salt mixture is typically used for inland marine production, which can be a substantial production cost. Developing an alternative salt mixture that includes the important ions necessary for proper shrimp growth may reduce production costs. For this experiment, shrimp production and water quality dynamics were examined using various mixtures of a low cost salt (LCS) mixture and a complete sea salt (CSS) formulation.
Six salt mixtures dictated by different inclusion levels of the LCS and CSS were used for this experiment. The LCS formulation was as follows: NaCl (75%), MgCl 2 (5%), MgSO4 (12%), KCl (1%), NaHCO3 (0.5%), CaCl2 (4%), and the CSS was Crystal Sea® Marinemix (Marine Enterprises International). The mixtures that defined each treatment were as follows: 100% LCS, 97.5%/2.5% LCS/CSS, 95%/5% LCS/CSS, 90%/10% LCS/CSS, 80%/20% LCS/CSS, and 75%/25% LCS/CSS. Each treatment included four, randomly assigned 1m3 culture tanks operated at a salinity of 15 ppt; each system included an external settling chamber and biofilter, operated continuously. The initial weight of the shrimp was 2.9 g, and all tanks were stocked at 263 shrimp/m3 . To determine if significant differences existed between treatments regarding water quality and shrimp production data, an α-value of 0.05 was used.
There were significant differences detected between treatments with regard to DO, pH, salinity, and turbidity. However, these differences in water quality were subtle and did not appear to impact overall shrimp production as no significant differences were found with average weight (g), biomass (Kg/m3), survival (%), FCR, or growth rate (% growth/week) metrics. When analyzing the cost of salt per kg of shrimp produced, the 100% LCS, 97.5%/5% LCS/CSS, and 95% /5% LCS/CSS all were significantly lower than the 75%/25% LCS/CSS. It costs $8.83 USD to make 1m3 of the 100% LCS mixture at 15 ppt salinity, compared to $12.89 to make the 75%/25% LCS/CSS mixture. The results from this study indicate that the 100% LCS formulation may reduce artificial sea salt cost by 70% when compared to increased CSS mixtures while having no significant impacts on shrimp production. Using this alternative salt formulation may reduce production costs and make inland shrimp farming a more lucrative venture.