Containment efficiency of acoustic virtual fence for large yellow croaker (Larimichthys crocea) mariculture in marine ranching

Net-free aquaculture has promising potential for an acoustic virtual fence. The Wuren'ao Acoustic Marine Ranch in Wenzhou, China, has implemented on the large yellow croaker (Larimichthys crocea). The net-free aquaculture mode can be expected to solve the severe ecological pollution from concentrated organic wastes, the structural vulnerability of conventional netting facilities under marine hydrodynamic forces, particularly for the escapement risks of farmed fish populations. In this study, a field aquaculture experiment was designed to quantitatively evaluate the practical containment efficacy of the acoustic virtual fence. The subjects were taken as the 30,000 juveniles of the Daiqu strain of large yellow croaker, with an average body length of 22.32 cm and an average body weight of 186.75 g. A 10-meter-high stationary trammel net was strategically deployed along the outer periphery of the acoustic fence zone. The precise monitoring and physical capture of any escaped fish were facilitated to combine continuous escapement monitoring with growth trait analysis. An uninterrupted two-month tracking was evaluated over the experimental period. The escapement was assessed to measure the cross-sectional area of the water column at the primary inlet channel of the marine ranch. The spatial data was integrated with the effective interception area of the trammel nets and their exact deployment duration. The Catch Per Unit Effort (CPUE) model was constructed to accurately estimate the absolute total escapement volume. The retention rate of juvenile stock was calculated in the cycle. Concurrently, a growth assessment protocol was implemented to measure body length and weight during periodic sampling. Specific Growth Rate (SGR) was obtained under the physiological and general health status of the fish within the acoustic fence environment. The results demonstrated that the retention rate of juvenile stock achieved an extraordinarily high level of 97.98% during the two-month experimental period. Simultaneously, the maximum recorded SGR exceeded 0.50%. The acoustic virtual fence effectively restricted the spatial activities of the large yellow croaker in the target waters. The low escapement rate with a maximally high biological retention rate was realized without adverse impacts on normal physiological growth. In conclusion, an acoustic virtual fence can be expected to serve as a highly viable alternative to conventional physical cage aquaculture. Environmental and engineering benefits are obtained for the technical pathway for the green, intelligent, and sustainable transformation of the marine ranching industry. The large-scale application can often require assessing the performance under varying seasonal hydrological conditions, different developmental fish sizes, extended aquaculture cycles, and its broader impacts on the surrounding ecosystem. Ultimately, the findings can also provide a strong theoretical and practical support to enhance the cultivation efficiency and ecological safety of high-value marine finfish.