Research into improved RAS techniques for the production of the marine shrimp, Liptopenaeus vannamei, under the auspices of a USDA Small Business Innovative Research Grant has led to the propagation of sizing criteria to facilitate commercial evaluations. These conservative guidelines provide sizing ratios for principal components required to produce 18-gram shrimp at a tank density of 10 kg/m3 without artificial substrate. Total ammonia nitrogen (TAN) and nitrite-N peak concentrations are maintained below 1 mg-N/L under the presumption that elevated nitrite-N concentrations are the principal stressor contributing to mortality, particularly during molt.
Initial testing focused on the evaluation of a 4.5-ton tank, an 85-liter PolyGeyser® bioclarifier, and a 7.6 cm airlift driven by a 100 lpm linear air pump to refine the system configuration and verify sizing assumptions. During the Fall 2021 run, one system was lost at 7.2 kg/m3 as the system was grossly overfed because shrimp numbers deviated from projections. Two systems, also suffering from gross overfeeding, were successfully harvested at 19 grams and an average density of 8.25 kg/m3 under less-than-ideal greenhouse conditions. During the Winter 2022 run, two systems were successfully harvested at 19 grams and a density of 9.2 and 10.1 kg/m3. The Winter 2022 run incorporated localized sludge digestors driven by a pneumatic exchange to conserve salt as sludge discharge is eliminated. Research into the use of the localized sludge digester as a means of tertiary treatment is ongoing. The research team remains confident that the propagated sizing criteria will prove conservative as it is commercially evaluated, and minor adjustments can be expected as techniques are refined.