Effects of Diurnal Oxygen Variation on Survival, Growth, and Stress Gene Expression in Pacific White Shrimp Litopenaeus vannamei

Oxygen is typically one of the first limiting water quality parameters affecting the culture of aquatic animals. However, there is a limited understanding of the effects of short-term low dissolved oxygen (DO) in Pacific white shrimp reared in outdoor green-water environments exposed to natural diurnal cycles, especially less than 3 mg L⁻¹ DO, and their impacts in commercial aquaculture settings. The present study evaluated the effects of cyclic short-term low DO conditions in outdoor green water tanks on shrimp survival, growth, nutrient retention, select blood parameters, and gene expression of the gill and hepatopancreas. The experiment was performed in 12 (800 L, 0.8 m²) round tanks stocked at 35 shrimp m⁻² (1.99 ± 0.06 g) using three aeration regimens. Four tanks were assigned to each treatment which included: low, medium, and high aeration using 0.25, 0.35, and 0.7 cubic feet per second (cfs) airstones, respectively. Diurnal cycles were allowed to cause varying periodic periods of short-term low DO. We found no difference in shrimp growth, survival, feed utilization, blood parameters, or gene expression of shrimp maintained in systems where DO was maintained near saturation as compared to those experiencing diurnal shifts in DO and nonlethal short-term low DO conditions. Clearly, lethal levels of DO must be avoided but we did not find justification to maintain DO in diurnal systems near saturation throughout the diurnal cycle.