南极磷虾宽频超声波散射特征及资源量估算

Antarctic krill (Euphausia superba) is one of the most abundant species, in terms of biomass, with high economic value. It also plays an important role in the Antarctic ecosystem. Scientific and accurate assessment of krill resources are essential for the sustainable development and utilization of the resources. The acoustic survey is an important approach to monitor Antarctic krill resources. Due to the limitation of narrowband frequencies used in present acoustic survey, little information can be interpreted from the echoes and the accuracy and precision of the estimate is relatively low. However, much more information could be interpreted from broadband echoes. Therefore, in this project, we propose to apply a broadband acoustic system we have developed to study broadband acoustics scattering of Antarctic Krill. By analyzing the acoustic scattering characteristics of individual krill and their swarm with different biological characteristics, backscattering models of krill under broadband frequencies will be developed. We will also develop a new method 1) to identify acoustic targets by analyzing the scattering spectrums, 2) to improve the accuracy of identification by image processing, and 3) to estimate the swarm density and average body length directly from the echo data. Finally, with the comparison analysis of trawl samplings, we will develop a resource estimation method based on broadband acoustic scattering characteristics of krill. This research has important significance to reveal more details about the acoustic scattering characteristics of Antarctic krill, and will potentially improve the accuracy of krill resource estimation in acoustic survey. More importantly, this research could provide valuable scientific guidance for future use of broadband acoustic technology to conduct effective survey for monitoring Antarctic krill resources.

南极磷虾数量巨大，经济价值高，且在生态系统中起非常重要的作用，科学准确评估其资源量，对可持续开发利用南极海洋生物资源有着重要的意义。声学调查是当前南极磷虾资源量评估的重要手段。但传统声学调查通常使用某一特定频率的窄带信号，从回波中能够获取的信息比较少，从而影响资源量估算的精度，而宽频信号则能够有效克服这一缺陷。为此，本项目拟采用宽频声学测量系统对磷虾回波散射进行精确的测量，分析不同生物学特征的磷虾个体及虾群在不同频率下的超声波散射特征，建立基于宽频信号下的磷虾散射模型；并依据回波散射频谱信息，结合图像分析法提高目标种类的判别精度；估算磷虾的群体密度和体长组成；结合网具实际调查，创新地提出基于磷虾宽频超声波散射特征的磷虾资源量估算方法。通过本研究，有助于更好掌握磷虾的超声波散射特征，对提高磷虾资源量的声学调查精度具有重要的意义，为今后使用宽频声学技术快速有效地开展磷虾资源量调查奠定基础。

南极磷虾资源丰富，经济价值高，且在生态系统中起非常重要的作用，科学准确评估其资源量，对可持续开发利用南极海洋生物资源有着重要的意义。声学调查评估是南极磷虾资源评估的主要方法。然而，目前的方法使用固定频率的窄带声信号获取目标信息受限，精度不高。本研究通过自研宽频水下生物回波散射系统获取了20-150kHz南极磷虾的回波散射特征的水槽实验数据，建立了水槽实验测量南极磷虾宽频回波散射特征的方法，验证了南极磷虾个体的宽频回波目标强度模型。结合海上调查实际测量的南极磷虾生物学特征，建立了不同体长的南极磷虾宽频回波散射特征，以及基于磷虾个体宽频散射特征识别南极磷虾的方法，成功地从海上现场调查数据中提取了南极磷虾的个体目标，并利用现场建立的不同体长南极磷虾宽频散射特征估算该磷虾的体长大小。此外，本研究实现了从南极磷虾集群中提取背向体积散射强度的宽频散射特征；结合建立的南极磷虾个体不同体长的宽频散射特征，提出了拟合曲线方法判别法；实现缺少现场采样数据的情况下，从宽频回波散射声学数据中直接估算南极磷虾体长组成和资源密度。本研究使用宽频方法判别南极磷虾个体及集群，并估算集群的体长分布和密度，对提高南极磷虾资源声学评估精度具有重要意义，为使用宽频声学探测系统评估海洋生物资源提供了科学依据。