Estimation of Bluefin Tuna (Thunnus thynnus) mean length in sea cages by acoustical means

This paper proposes an indirect method to estimate Bluefin Tuna (Thunnus thynnus) biomass in cages using acoustic techniques. Two Simrad EK60 echosounders working at 120 and 200 kHz a stereo camera were used obtain target strength (TS) fork length (FL) relationships for both operating frequencies. The equipment was placed the bottom of floating cage, facing towards surface record ventral aspect fish. optical recordings automatically analysed combination results provided unequivocal TS-FL assignments. Good between TS FL obtained frequencies even without discriminating data from different fish tilts beam directivity compensation. Stronger correlations compensated when reduced tuna swimming tilt considered. measurements compared MFS numerical predictions swimbladder model, with simulation showing good agreement experimental measurements. allow mean be predicted growing or fattening raising possibility improving production management providing useful tool catch control estimations made by international organisations (like ICCAT) government bodies.