Estimation of demersal fish biomass using hydroacoustic and catch data in the marine ranching area (MRA ) of Jeju

Hybrid surveys using hydroacoustic and fish sampling gears such as trammel net , trap were conducted toinvestigate total biomass , distribution and dominant fish species of the demersal fishes in the marineranching area (MRA ) of Jeju . Four surveys were carried out in June , August , October and November using38 kHz quantitative echo sounder . Catch data using trammel net and trap were used to calculate biomass andto examine dominant fish species . Fish schools were mainly detected in the waters of 20 meters below andaround Chagwido waters . By the result of fishing experiments , fish species living in MRA of Jeju wereabout 40 species , dominant fish species of a detectable fish such as Family Sparidae and FamilyMonacanthidae etc . were identified 59.4~68.8% of total biomass . Based on the hydroacoustic data , fishlength -weight function and target strength information , mean density of the demersal fish estimated were as