## 4 Comparison with Previous Studies
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Number**} & **Fish Species** & **Frequency (kHz)** & **W (g)** & **\(L\) (cm)** &
\begin{tabular}{c} **W/L3** \\ **(kg/m3)** \\ \end{tabular} & \(n(m)^{3}\) & \(\sigma_{e}(m^{2})\times 10^{-4}\) & \(\sigma_{eW}\) & \multirow{2}{*}{**\(\sigma_{eL}\)**} & \multirow{2}{*}{**Ref.**} \\ \cline{1-1}  & Northern & & & & & & & & & & \\  & anchovy & 20 & 9.6 & 10.6 & 8.1 & 650 & 5.0 & 0.0111 & 0.0445 & [5] \\ \hline \multirow{2}{*}{2} & Japanese & \multirow{2}{*}{50} & \multirow{2}{*}{5.2} & \multirow{2}{*}{8.6} & \multirow{2}{*}{8.2} & \multirow{2}{*}{250} & \multirow{2}{*}{6.5} & \multirow{2}{*}{0.0217} & \multirow{2}{*}{0.0879} & [14] \\  & anchovy & & & & & & & & & & \\ \hline \multirow{4}{*}{3} & \multirow{4}{*}{Yellowtail} & 25 & \multirow{4}{*}{4500} & \multirow{2}{*}{72.0} & \multirow{2}{*}{12.1} & \multirow{2}{*}{10} & \multirow{2}{*}{10} & \multirow{2}{*}{282.7} & \multirow{2}{*}{0.0104} & \multirow{2}{*}{0.0545} & \multirow{4}{*}{} \\  & & 50 & & & & & & 479.8 & 0.0176 & 0.0926 & \\  & 100 & & & & & & 510.7 & 0.0187 & 0.0985 & [15] \\  & & 200 & & & & & 897.9 & 0.0329 & 0.1732 & [16] \\  & & 25 & & & & & 49.9 & 0.0054 & 0.0519 & \\  & Sea bream & 50 & 900 & 31.0 & 30.2 & 21 & 53.2 & 0.0057 & 0.0554 & \\  & & 100 & & & & & 73.8 & 0.0079 & 0.0768 & \\  & & 200 & & & & & 105.2 & 0.0113 & 0.1095 & \\  & & 25 & & & & & 28.5 & 0.0070 & 0.0334 & \\  & Spotted & 50 & & & & & 25.8 & 0.0063 & 0.0303 & \\  & mackerel & 100 & & & & & 32.8 & 0.0080 & 0.0385 & \\  & & 200 & & & & & 39.1 & 0.0096 & 0.0459 & \\ \hline \multirow{4}{*}{4} & Saithe & \multirow{2}{*}{120} & \multirow{2}{*}{375} & \multirow{2}{*}{35.1} & \multirow{2}{*}{8.7} & \multirow{2}{*}{100} & \multirow{2}{*}{30.0} & \multirow{2}{*}{0.0058} & \multirow{2}{*}{0.0244} & \multirow{4}{*}{} \\  & Atlantic & & & & & & 50.0 & 0.0096 & 0.0406 & \\  & herring & 38 & - & 33.9 & - & - & 22.7 & - & 0.0198 & \\ \hline \multirow{2}{*}{5} & Yellowtail & 50 & - & - & 15.6 & - & - & 0.0040 & - & [18] \\  & Sea bream & 50 & - & - & 30.5 & - & - & 0.0030 & - & \\ \hline \multirow{2}{*}{6} & Pacific & \multirow{2}{*}{420} & \multirow{2}{*}{100} & \multirow{2}{*}{20} & \multirow{2}{*}{12.5} & \multirow{2}{*}{92} & \multirow{2}{*}{42.1} & \multirow{2}{*}{0.0198} & \multirow{2}{*}{0.1065} & \multirow{2}{*}{} \\  & herring & & & & & & 44.6 & 0.0207 & 0.1115 & \\ \hline \multirow{4}{*}{7} & Japanese & \multirow{2}{*}{4 horse} & \multirow{2}{*}{5} & \multirow{2}{*}{217} & \multirow{2}{*}{27.7} & \multirow{2}{*}{10.2} & \multirow{2}{*}{100} & \multirow{2}{*}{17.5} & \multirow{2}{*}{0.0048} & \multirow{2}{*}{0.0223} & \multirow{2}{*}{This} \\  & mackerel & 6 & & & & & 16.5 & 0.0046 & 0.0210 & \\ \cline{1-1} \cline{5-1} \cline{5-11}  & & \multirow{2}{*}{7} & & & & & 20.5 & 0.0057 & 0.0261 & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary and comparison of the attenuation experiments in fish schools; fish species, frequency, wet weight (\(W\)), total length (\(L\)), relationship \(W\)-\(L\) (\(W\)/\(L\)3), number density (\(n\)), extinction cross-section (\(\sigma_{e}\)), normalized extinction cross-section of \(W\) (\(\sigma_{eW}\) ) and \(L\) (\(\sigma_{eL}\) ), and references from previous and present studies. was similar to that of Northern anchovy at 20 kHz and Japanese anchovy at 50 kHz [5;14]. \(\sigma_{eW}\) converged to a regression curve even for different species and methods. The previous regression model was not calculated for all \(\sigma_{e}\) values and only showed a regression formula \(\sigma_{eW}\) for more than 25 kHz of the high-frequency band [6]. On the basis of the experimental results, the new regression models for the mid-frequency range were suggested to normalize extinction cross-sections of \(W\) and \(L\) of fish.