Kelly J. Benoit-Bird and Whitlow W. L. Au Reporter : 曾綺停 2003 Acoustical Society of America Pages: 2757–2766

Introduction The most commercially important bottomfish, are the primary species of concern in Hawaiian. About these deepwater fish and their habitat is very little known. Need for detailed acoustic backscattering data for targeted species.

Red snapper Long-tailed red snapper Pink snapper Brighma’s snapper Von Siebold’s snapper Blue-striped snapper

Objective  The first objective was to obtain controlled measurements of acoustic backscatter strength from all aspects of these fish, particularly the two depleted species and the pink snapper, which is the most commercially valuable species.  The second was to measure the shape, size, and orientation of the swimbladders of the same fish.  Objective three was to assess how acoustic backscattering strength was related to the swimbladder measures and other physiological characters such as length, biovolume, and wet weight.

本文精華 資料蒐集 採樣 泳鰾與 TS 之間 理論關係 聲學背景 分析方法 TS 實驗流程 及技術 結果分析

Methods anestsetizedacclimated transported Kept alive captured

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A. Backscatter Frequency range of kHz

B. Swimbladders Preserving swimbladders to slit the fish ventral side, and inject Plaster of Paris X rays after frozen, maeasured dorsal and lateral aspect measured length, total length, displacement volume, and wet weight over-anesthetization using 2 mL of 2-phenoxy-ethanol per 10L of seawater

Red snapper Long-tailed red snapper Pink snapper

Brighma’s snapper Von Siebold’s snapper Blue-striped snapper

C. Data analysis First, the maximum measured TS was compared to the TS of the fish predicted by modeling the swimbladder as a prolate spheroid. The second model predicts target strength of the fish by modeling the swimbladder as a sphere with a volume equivalent to that measured from the plaster cast of the swimbladder. First, the maximum measured TS was compared to the TS of the fish predicted by modeling the swimbladder as a prolate spheroid. The second model predicts target strength of the fish by modeling the swimbladder as a sphere with a volume equivalent to that measured from the plaster cast of the swimbladder. (Furusawa,1988) (Urick,1983)

Results 1.Swimbladders Red snapper Long-tailed red snapper Pink snapper

Brighma’s snapper Von Siebold’s snapper Blue-striped snapper

Results 2.Target strength The angle at which the maximum dorsal-aspect target strength was measured had a nearly one-to-one relationship with the angle of the swimbladder relative to the dorsal aspect of the fish, regardless of species

Pink snapper TS=20.6* ㏒ (F SL )-55.1, r 2 =0.85 Red snapper TS=13.7* ㏒ (F SL )-46.4, r 2 =0.54 Longtailed red snapper TS=12.6* ㏒ (F SL )-42.9, r 2 =0.80 Pink snapper TS=26.2* ㏒ (F SL )-63.5, r 2 =0.85 Red snapper TS=47.2* ㏒ (F SL )-98.3, r 2 =0.81 Longtailed red snapper TS=28.9* ㏒ (F SL )-68.8, r 2 =0.81

. Variance values increased from 13 to 49 dB with increasing frequency 0.1 to 11 dB

Red snapper Long-tailed red snapper Pink snapper

Red snapper Long-tailed red snapper Pink snapper

Red snapper Long-tailed red snapper Pink snapper lower

Red snapper Long-tailed red snapper Pink snapper

Results 3.Models About both the dorsal and lateral aspects of the fish are the most important for utilizing these measures in a field study. The target strength over this range of angles had a range of 8 to 12 dB in the tilt plane, 2.5 to 7 dB in the roll plane, and 4 to 6 dB in the lateral plane. Red snapper wet weight (g)=22983*sigma(m 2 ) (r 2 =0.82 P<0.05) Long-tailed red snapper wet weight (g)=24631*sigma(m 2 ) (r 2 =0.71 P<0.05) red snapper wet weight (g)=12665*sigma(m 2 ) (r 2 =0.77 P<0.05)

Discussion The differences in volume between fish are greater within each genus than between them. Target strengths, both lateral and dorsal, of all three target species were correlated with standard length. Variance in target strength within individuals about the lateral axis was also high. This could permit a conversion of acoustic scattering to snapper species biomass, even if specific species identification were not possible.

公式 1 取出最大 TS 值 TS 與泳鰾外型 ~ 後面為橢圓體求法 來源皆來是 X 光 公式 2 為容積 R 為半徑 導引到別人都認為 TS 與體長有密切關係 ~ 而我 們又知道影響 TS 為主的為有氣體的 ( 胃、泳 鰾 )… 希望能用這些模式相推 !!