A Study on Mitigating Dissolved Gas Supersaturation in Culture Water of Land-Based Aquaculture Systems

This study developed and evaluated a degassing device based on the Venturi principle to mitigate gas supersaturation occurring in culture water in land-based aquaculture systems. To evaluate the degassing efficiency of the device, an experiment was conducted in a circular PP tank with a diameter of 5 m, maintaining a water depth of 50 cm under a flow-through culture system from February 6 to February 24. The culture water supply systems were classified into three types: a submerged inlet, an exposed inlet, and an inlet equipped with the degassing device. Gas saturation levels in the culture water were measured under each treatment. The mean oxygen saturation (SAT) was highest in the degassing device-equipped treatment (84.23 ± 0.39%) and lowest in the submerged inlet treatment (56.24 ± 0.24%), with a significant difference among treatments (p < 0.05). The mean total gas pressure (TGP) increased significantly in the following order: degassing device-equipped treatment > exposed inlet treatment > submerged inlet treatment (p < 0.05). In contrast, residual gas saturation (RES) was highest in the submerged inlet treatment (110.04 ± 0.38%) and lowest in the degassing device-equipped treatment (103.66 ± 0.42%) (p < 0.05). These results indicate that the Venturi-based degassing device effectively reduced gas supersaturation in culture water and may be applicable to the management of gas saturation in land-based aquaculture systems.