Relationships between the geometric dimensions and biomass of schools
Relationships between the geometric dimensions and biomass of schools
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学校几何尺寸与生物量的关系
DOI：
10.1093/icesjms/49.3.305
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发表时间：
1992
影响因子：
3.3
通讯作者：
J. Dalen
中科院分区：
文献类型：
--
作者：
O. A. Misund;A. Aglen;A. K. Beltestad;J. Dalen
用多波束声纳和回声积分器系统对鲱鱼、鲱鱼和鲱鱼鱼群的几何尺寸和种群密度进行了声学测量。建立了反射回波能量、估算学校生物量与学校规模之间的关系。这三个物种之间的关系似乎非常相似，而且与鱼的大小无关。发现了鲱鱼鱼群行为的季节和地区差异。群落维度到群落生物量转换可能是一种有用的方法，用于估算远洋物种的丰度，也用于捕获情况下的生物量测量。导语：如果在常规的回声整合调查中鱼群避开了渔船，那么可能会严重低估鱼类的丰度（Olsen 1987）。同样，如果目标种群的一小部分在靠近水面（“上死亡区”）的地方上学，可能根本不会被记录下来（Aglen 1989）。扇形扫描声纳的使用可以减少这种采样偏差，并由于其更大的体积覆盖而提高丰度估计的精度（Ehrenberg 1980）。由于声纳的指向性，从一个鱼群的反射回波能量中估计实际生物量是复杂的。水平制导波束中的ISh后向散射强度和相当大的噪声混响（Mitson 1983）。此外，在鱼类密度高的情况下，对发出的声束的吸收可能会导致对鱼群的低估（Foote 1978, Rr6ttingen 1976）。最先进的渔业声纳提供了一个记录鱼群的相对的、按比例的回声量（Bodholdt 1982）。普通声纳显示与学校大小成比例的学校投影，并以颜色指示回声强度。通过将围网捕获鱼群的面积和生物量相关联，建立了将声纳测量的鱼群面积转化为鱼群生物量的关系（Misund 1986, 1988）。声纳测量的单位面积的平均密度和围网捕获的鱼群被用作北凤尾鱼声纳生物量估算的转换因子（Hewitt et. al . 1976）。为了进一步研究这种关系的普遍性，对不同季节和地理区域的鲱鱼、鲱鱼和鲱鱼进行了种群尺寸和反射回波能量的声学测量。该方法的基础是，同步和极化游泳中的个体形成紧凑、高密度的单位（Partridge et al. 1980），从而在生物量和几何尺寸之间形成比例。材料和方法在北海和挪威海岸的R/V“Eldjam”号船（1043 GRT, 3600 Hp）和R/V“Fjordfangst”号船（20 GRT, 180 Hp）的巡航中记录了这些学校（表1）。两艘船都配备了标准校准（Foote et al. 1987）回波积分器系统和多波束声纳（Furuno CH-12在“Fjordfangst”上，simmrad SM600在“Eldjam”上）。学校录音时的声纳图像是在船只转向并接近学校时拍摄的。如果船只操纵成功，则记录积分器值(M)，深度(D)和垂直范围(h)，以便回声测深仪记录学校。然后，每隔10 s用尺子测量学校投影的纵向（lw）和横向（cw）范围（Misund 1990a），录像的静止画面播放。在测深仪上测量样条长度（tl）。通过修改Johanneson & Losse（1977）的方法，计算出实际尺寸、鱼密度和鱼群生物量：横向纵向程度程度连续波(CW o年代2 R tan (cpsf2) LW 1 = LW o s et sf2 LW] = LW科·阿sctsf2学校areaA = ((CW·LW) / 4) * 1 t深度H = hcte / 2学校体积V = 413··样(H / 2)长度TLA = tl o (vlpv) D (2 tan (cpel2)) TLB = 185, 2·(tl / QNM) D (2 tan (Cf本部/ 2))鱼密度p = ((CJ·M·KNM)我(41 t·C1bs·K2NM·tl·H) (nlnr)学校生物质B = V·p·W Cf, Cf > e: ts, te: R: s: C:声纳波束宽度（水平）和回波仪波束宽度（沿船）声纳和回波仪脉冲长度水平距离船校声纳比例因子（声纳距离/屏幕距离）声速（1500m /s） (m) (m) (m) (m) (m)
Fishing Gear and Methods Division P.O.Box 1964, N-5024 Bergen, Norway **Institute of Marine Research P.O.Box 1870, N-5024 Bergen, Norway Acoustic measurements of the geometric dimensions and packing de~~ity of herring, sprat and saithe schools have been conducted by multi-beam sonars and echo integrator systems. Relationships between the reflected echo energy, the estimated school biomass and the school dimensions were established. The relationships seems quite similar for the three species and rather independent of the size of the fish. Seasonal and regional differences in schooling behaviour of herring were detected. School dimension-to-school biomass conversion may be a useful method for abundance estimation of pelagic species, and also for biomass measurements in capture situations. INTRODUCTION If schooling fish are avoiding the vessel during conventional echo-integration surveys, a significant underestimation of the fish abundance may occure (Olsen 1987). Similary, if a fraction of the target population is schooling close to the surface ("the upper dead zone"), it may not be recorded at all (Aglen 1989). Use of sector scanning sonars may reduce such sampling biases, and increase the precision in abundance estimation due to their greater volume coverage (Ehrenberg 1980). Real biomass estimation from the reflected echo energy of a school by sonar is complicated due to the directivity of the !ISh back scattering strength, and considerable noise reveberation in horizontal guided beams (Mitson 1983). Absorbtion of the emitted sound beam in high fish densities may in addition cause underestimation of schools (Foote 1978, Rr6ttingen 1976). The most sophisticated fisheries sonars provide a relative, scaled echo quantity of a recorded school (Bodholdt 1982). Ordinary sonars display a school projection proportional to the school size with colour indication of echo strength. 2 Relationships for converting sonar measured school area to school biomass have been established for herring and mackerel by correlating the area and biomass of purse seine captured schools (Misund 1986, 1988). An average density per unit area of sonar measured and purse seine captured schools has been used as a conversion factor in biomass estimation by sonar of Northern anchovy (Hewitt et. al 1976). To investigate the generality of such relationships further, acoustic measurements of school dimensions and reflected echo energy were conducted on herring, sprat and saithe schools in different seasons and geographic regions. The basis of the method is that individuals in syncronized and polarized swimming forms compact, high density units (Partridge et al. 1980) which creates proportionality between the biomass and geometric dimensions. MATERIALS AND METHODS The schools were recorded on cruises by the vessels R/V "Eldjam" (1043 GRT, 3600 Hp) and R/V "Fjordfangst" (20 GRT, 180 Hp) in the North Sea and along the Norwegian coast (Table 1 ). Both vessels were equipped with standard calibrated (Foote et al. 1987) echo integrator systems and multibeam sonars (Furuno CH-12 onboard "Fjordfangst" and Simrad SM600 onboard "Eldjam"). The sonar picture during a school recording was videotaped as the vessel was turned towards and approached the school. The integrator value (M), depth (D) and vertical extent (h) were noted if the vessel was manovered successfully so that the school was recorded by the echo sounder. Later, the lengthwise (lw) and crosswise (cw) extents (Misund 1990a) of the school projection were measured by a ruler during 10 s interval, still picture playback of the video recordings. The transect length (tl) were measured on the echo sounder recording. By modifying the method of Johanneson & Losse (1977), the real dimensions, fish density and school biomass were calculated by: Crosswise extent Lengthwise extent CW = CW o s 2R tan (cpsf2) LW 1 = lw o s et sf2 LW] = lw o cosa · sctsf2 School areaA = ((CW · LW)/4) * 1t Vertical extent H = hcte/2 School volume V = 413 · A · (H/2) Transect length TLA = tl o (vlpv) D(2tan(cpel2)) TLB = 185,2 · (tl/QNM) D(2tan (Cf'e/2)) Fish density p = ((CJ · M · KNM)I(41t · C1bs · K2NM · TL · H)(nlnr) School biomass B=V·p· W Cf's, Cf>e: ts, te: R: s: C: beamwidth of sonar (horizontal) and echo sounder (alongship) pulselengths of sonar and echo sounder horizontal distance vessel -to-school sonar scaling factor (sonar distance/screen distance) speed of sound (1500 m/s) (m) (m) (m)