Low-Frequency Acoustic Technique to Size and Count Fish in Commercial Aquaculture

One hurdle to improving the efficiency of commercial aquaculture is the lack of methods for reliably counting and sizing the stock. Conventional hydroacoustical methods exist for determining fish populations in natural waters, but these methods have not been successfully adapted to commercial fish farming, where population densities are orders of magnitude higher and where wall and boundary effects on the acoustics are significant. A new technique was proposed in Phase I that relied on changes in the low frequency modes of the waveguide formed by ponds/tanks. The results of the Phase I feasibility study show an extremely high correlation between the fish density and the shift in the cut-off frequency of the enclosure with fish indicating the validity of the method proposed. The size distribution of the fish may be estimated using the resonance frequency of the fishes swim bladders. The results clearly indicate a method that may result in a viable system to detect fish biomass economically in cultured tanks, ponds, and net pens. The proposed research combines a team of experts in a focused effort to develop a robust pre-production device. The conceptual design of the system developed in Phase I will be translated and implemented into five preproduction units in Phase II and then field tested at several commercial farms.