商用探鱼仪南极磷虾声学图像的数值化处理

Numericalization of pictorial image of Antarctic krill echogram taken from a commercial echo-sounder

为充分利用渔船所获渔业资源的分布信息,提出了一组商用探鱼仪声学图像数值化处理方法,并将其应用于以数码相机拍摄的南极磷虾回波图像处理,对南极磷虾的集群特征进行了研究。通过对图像进行拍摄角度与亮度调整等预处理、像素色彩标准化与二值化处理后,对虾群厚度、密度中心以及相对集群密度等集群特征进行了分析。30幅图像的处理结果表明,图像所示虾群的平均厚度范围为5.6～55.8m,中值厚度为25.7m,均值厚度为27.1m;虾群密度中心所处水深为40.0～156.5m,中值水深为68.8m,均值水深为77.3m。磷虾的集群特征存在较为明显的昼夜变化,白天集群密度高、厚度小,夜间密度低、厚度大。本研究所述方法为利用渔船商用探鱼仪进行渔业资源研究提供了一种有效技术手段。

In order to make the best use of the information on fishery resources derived from fishing vessels, a series of processing methods were probed to numericalize the pictorial image of the acoustic echogram taken from a commercial echo-sounder. The resulting methods were then applied to analyze the swarming characteristics of Antarctic krill Euphausia superba utilizing echogram image photos taken from a Chinese Antarctic krill fishing vessel. The thickness, gravity center and relative density were analyzed after a series of preprocessing including adjustment of shooting angle and luminance of the photos, and standardization of the RGB Trip- lets and binarization of each pixel. Results from 30 images showed that the mean thickness of these krill swarms ranged from 5.6 m to 55.8 m,and the median thickness and mean thickness were 25.7 m and 27.1 m, respectively. The gravity center of these swarms were found between depths of 40.0 m and 156.5 re,and the median depth and mean depth were 68.8 m and 77.3 m, respectively. There was an apparent diel variation in the swarming characteristics of Antarctic krill, the swarms were relatively thinner but krill densities were relatively high in day hours; and the opposite were true at night. This exercise provided an effective tool for the study of fishery resources using fishing vessels where only commercial echo-sounder is available.