Relationship between the Zooplankton Biomass and the Acoustic Volume Backscattering Strength at 38 kHz in the Waters off Northern Taiwan

臺灣北部海域體積散射強度與生物密度關係之研究

高似嘉(Szu-Chia Kao) ； 李明安(Ming-An Lee)

《臺灣水產學會刊》 39卷1期 (2012/03) Pp. 1-10

https://doi.org/10.29822/JFST.201203.0001

摘要

Acoustical and biological samplings of zooplankton in the waters off northern Taiwan were carried out by the ”Ocean Researcher II” in 2008~2009. The volume backscattering strength (Sv) was measured at 38 kHz; meanwhile, a joined Bongo net with different mesh sizes of 200, 330 500, and 1,000 μm was dragged vertically to collect biological organisms.The dominant systematic species groups were copepods which accounted for 77%, 75%, 67%, and 52% of the total number of zooplankton with respective mesh sizes of 200, 330, 500, and 1,000 μm. Linear relationships between the logarithm of the zooplankton density (B; mg/m^3) and Sv (dB) at 38 kHz for the four mesh sizes were found. Using an ANCOVA test to compare the slopes and intercepts of the four equations, the results showed that the intercepts and slopes of the equations for mesh sizes of 200, 330, and 500 μm did not significantly differ, but there were significant differences between the intercepts for the equation for the 1,000-μm mesh.Results suggested that those three equations could be combined into the equation: Sv38 = 9.45 logB200~500 - 94.60 (n = 51, r = 0.76, p ＜ 0.05), while the equation for 1000 μm was Sv38 = 8.56 logB1000 - 87.48 (n = 17, r = 0.74, p ＜ 0.05). The discrepancy between the two intercepts was 7.12 dB. Possible influences for the difference of the two equations are also discussed in this study.

關鍵字

聲探計測 ； 浮游動物生物量 ； 網目大小 ； 體積散射強度

並列摘要

Acoustical and biological samplings of zooplankton in the waters off northern Taiwan were carried out by the ”Ocean Researcher II” in 2008~2009. The volume backscattering strength (Sv) was measured at 38 kHz; meanwhile, a joined Bongo net with different mesh sizes of 200, 330 500, and 1,000 μm was dragged vertically to collect biological organisms.The dominant systematic species groups were copepods which accounted for 77%, 75%, 67%, and 52% of the total number of zooplankton with respective mesh sizes of 200, 330, 500, and 1,000 μm. Linear relationships between the logarithm of the zooplankton density (B; mg/m^3) and Sv (dB) at 38 kHz for the four mesh sizes were found. Using an ANCOVA test to compare the slopes and intercepts of the four equations, the results showed that the intercepts and slopes of the equations for mesh sizes of 200, 330, and 500 μm did not significantly differ, but there were significant differences between the intercepts for the equation for the 1,000-μm mesh.Results suggested that those three equations could be combined into the equation: Sv38 = 9.45 logB200~500 - 94.60 (n = 51, r = 0.76, p ＜ 0.05), while the equation for 1000 μm was Sv38 = 8.56 logB1000 - 87.48 (n = 17, r = 0.74, p ＜ 0.05). The discrepancy between the two intercepts was 7.12 dB. Possible influences for the difference of the two equations are also discussed in this study.

並列關鍵字

Acoustic estimation ； Zooplankton biomass ； Mesh size ； Volume backscattering strength