Abstract:
The Wuren'ao Acoustic Marine Ranch in Wenzhou, China, has successfully implemented the world's first net-free acoustic virtual fence aquaculture model tailored for the large yellow croaker (
Larimichthys crocea). This groundbreaking approach effectively resolves critical bottlenecks historically associated with traditional net-cage aquaculture systems. These long-standing challenges encompass severe ecological pollution from concentrated organic waste, the structural vulnerability of conventional netting facilities under marine hydrodynamic forces, and the ecological risks linked to the escapement of farmed fish populations. To scientifically and quantitatively evaluate the practical containment efficacy of this innovative acoustic virtual fence system, a comprehensive field aquaculture experiment was meticulously designed. For this study, 30,000 juveniles of the Daiqu strain of large yellow croaker were stocked. These experimental subjects exhibited an average body length of 22.32 cm and an average body weight of 186.75 g. To facilitate the precise monitoring and physical capture of any escaped fish, a robust, 10-meter-high stationary trammel net was strategically deployed along the outer periphery of the acoustic fence zone. By combining continuous escapement monitoring with detailed growth trait analysis, an uninterrupted tracking evaluation was conducted over a defined experimental period lasting two months. The core methodology for the escapement assessment was predicated upon the measurement of the cross-sectional area of the water column at the primary inlet channel of the marine ranch. Integrating this spatial data with the effective interception area of the trammel nets and their exact deployment duration, a specialized Catch Per Unit Effort (CPUE) mathematical model was constructed. This CPUE modeling approach enabled researchers to accurately estimate the absolute total escapement volume throughout the evaluation cycle, allowing for the calculation of the ultimate juvenile stock retention rate. Concurrently, a rigorous growth assessment protocol was implemented through periodic sampling to measure body length and weight. These measurements were utilized to calculate the Specific Growth Rate (SGR), facilitating an analysis of the physiological status and general health condition of the fish reared within the acoustic fence environment. The empirical results derived from this field study demonstrate that during the two-month experimental period, the calculated juvenile stock retention rate achieved an extraordinarily high level of 97.98%. Simultaneously, the maximum recorded Specific Growth Rate exceeded an impressive 0.5%. These findings unequivocally confirm that the acoustic virtual fence system is highly capable of effectively restricting the spatial activities of the large yellow croaker strictly to the designated target waters. It exhibits the dual advantages of an exceptionally low physical escapement rate paired with a maximally high biological retention rate, without exerting adverse impacts on normal physiological growth. In conclusion, acoustic virtual fence technology stands as a highly viable alternative to traditional physical cage aquaculture facilities. It possesses profound environmental benefits and distinct engineering advantages, providing an innovative technical pathway for the green, intelligent, and sustainable transformation of the marine ranching industry. This holds immense theoretical significance and practical value for enhancing the cultivation efficiency and ecological safety of high-value marine finfish. Future research should strategically focus on assessing the technology's operational performance under varying seasonal hydrological conditions, different developmental fish sizes, and extended aquaculture production cycles, as well as investigating its broader impacts on the surrounding ecosystem, ultimately providing support for its large-scale commercial application.