한국 연근해산 갈치(Trichiurus lepturus)의 음향반사강도에 대한 주파수 및 체장 의존성

Abstract

Largehead hairtail(Trichiurus lepturus) is one of most fisheries stocks inhabiting widely in East China Sea and Yellow Sea, which is produced by various fishing gear such as stow net, long line, jigging and trawl to 60,086 M/T in 2005. Now, each kind of research and investigation for scientific estimation, management and protection of main fisheries biomass were conducted in all countries of the world. Also, the hydroacoustic survey has been performed annually by the NFRDI with using bottom and mid-water trawls in inshore and offshore around the Korea Peninsula. However, acoustical survey has been not performed in estimation for fish size distribution so that it is necessary to construct the data bank of their target strength(TS) relative to fish species, length(L) and frequency. This study describes on the frequency and length dependence on TS, in which distribute in Korean waters(mainly near Jeju Island), in relation to the construction of the TS data bank. The TS measurement of largehead hairtail was carried out in water tank(L5m×W6m×H5m) using 4 frequencies of 50, 75, 120 and 200k㎐ by tethered method. The average TS patterns were measured as a function of tilt angle, ranging from -45°(head down) to +45°(head up) by every 0.2°. Furthermore, the length conversion constant(b_(20)) was estimated under the assumption that TS is proportional to the square of its length. Also, the in situ TS measurement on live largehead hairtail was performed by using split beam echo sounder in the Suyeong Man, Busan. The result of experiments at each frequency can be summarized as follows; 1. As result of TS-length dependence for 104 largehead hairtails, the length conversion constant was -66.60 at 50k㎐, -69.53 at 75k㎐, -67.85 at 120k㎐ and -69.57 at 200k㎐ under assumption that TS is proportional to , L² respectively. 2. We obtained a linear regression equation of σ/λ² = 0.032042 (AL/λ)^(1.75101)in the result of the relationship between σ/λ² and AL/λ of 104 individuals at 50, 75, 120 and 200k㎐. And then, is sound scattering cross section(m²), AL is anal length(m) and λ is wavelength of frequency(m). 3. Mean TS() of 118 largehead hairtails obtained by split beam echo sounder measurements at 120k㎐ was -45.9㏈. The length conversion constant b_(t) derived from the relationship between and mean anal length() was b_(t)=-69.82dB. 4. The difference in TS between the in situ measurement and the prediction by tank measurement was 1.1㏈.