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Cuttlefish Sepia esculenta are commercially important in Korea. Assessments of their biomass currently depend on fishery-landings data, which may be biased. Towards fishery-independent acoustic surveys of cuttlefish, target strength (TS) measurements at 70 and 120 kHz were made of 23 live cuttlefish, in early May 2010. The fish were caught by traps in the inshore waters around Geojedo, Korea. The TS were measured using split-beam echosounders (Simrad ES60 and EY500, respectively). The cuttlefish mantle lengths (L) ranged from 15.6 to 23.5 cm (mean L=17.8 cm) and their masses (W) ranged from 335 to 1020 g (mean W=556.1 g). Their mean TS values at 70 and 120 kHz were -33.01 dB (std=1.39 dB) and -31.76 dB (std=2.15 dB), respectively. The mean TS at 70 kHz was 0.17 dB higher than the TS-length relationship resulting from a least-squares fit to the data (TS = 24.67 log 10 L (cm) -64.03, r 2 = 0.52, N=23). The mean TS at 120 kHz was 0.45 dB higher than the fitted TS-length relationship (TS = 40.59 log 10 L (cm) -82.96, r 2 = 0.58, N=23). The differences between the mean TS values and an equation regressed from all of the TS measurements at both frequencies (TS = 24.92 log 10 L (m) -4.92 log 10 λ (m) -22.82, r 2 = 0.86, N=46) was 0.22 dB at 70 kHz and 0.31 dB at 120 kHz, respectively.

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Tel82 51 620 6116．Fax82 51 620 8145．Emaildaejael＠pknu.ac.kr Black rockˆsh, goldeye rockˆsh and black scraper are commercially importantˆsh species due to the increasing demand in Korea. When estimating the abundance of stocks for these species acoustically, it is of crucial importance to know the target strength (TS) to length dependence. In relation to these needs, target strength experiments were conducted on three species in an acrylic salt water tank using a 70-kHz split-beam echo sounder. The target strength for these three species under controlled conditions was simultaneously measured with the swimming movement by a DVR system and analyzed as a function ofˆsh length (L). Equations of the form TS＝a log