南极大磷虾声学调查数据噪声处理与资源评估

在中国第28次南极科学考察期间，利用“雪龙号”科考船载SIMRAD EK500（38kHz）科学渔探仪对南极半岛附近海域的南极大磷虾资源量进行了调查。原始声学数据经过信噪比估算和背景噪声剔除数据后处理方法剔除背景噪声以及手动剔除表面混响、海底反射和坏数据之后，在200 m以浅水层中，以1n mile间隔进行积分，并应用Matlab软件编程对积分结果进行后处理，得出调查海域中南极大磷虾的资源分布情况。结果表明：（1）“雪龙号”的平均噪声功率值为-146.47dB re 1W；(2)空白水体的噪声平均剔除百分比为88.3%；（3）调查区域内的南极大磷虾平均密度为27.30 g·m^-2（62.95 ind·m^-2）。

REMOVAL OF ECHO INTEGRATION NOISE AND ESTIMATION OF THE ABUNDANCE OF ANTARCTIC KRILL

The abundance of krill on the continental shelf and slope north of the Antarctic Peninsula was measured during the 28th Chinese Antarctic Research Expedition in the summer of 2011–2012. Acoustic data for the estimation of krill abundance were collected using an EK500 scientific echo sounder installed on the R/V Xuelong, using a 38 kHz operating frequency. However, the data were affected by significant electrical noise that had to be removed before integrating the mean volume backscattering strength (Sv). Noise correction and signal-to-noise-based thresholds were used for post-processing removal of noise from the acoustic data. Cell-size parameters of one ping and 70 samples were used to average the power data, a quantity equivalent to the Sv with no time varied gain applied. The signal-to-noise ratio (SNR) was defined as the original Sv minus the estimated maximal Sv_noise, such that 0 dB could be set as the minimum desired SNR. The results showed that the noise power averaged over all transects was ?146.47 dB re 1W and the average noise-removal percentage reached 88.3%. The mean biomass and numerical density in the survey area were 27.30 g·m^?2 and 2.95 ind·m^?2,respectively. This study demonstrates that the R/V Xuelong is a useful platform to study the biomass and distribution of krill using acoustic methods.