Monitoring fish using imaging sonar: Capacity, challenges and future perspective

Abstract

The demand for fish products, which provide crucial protein for humans, is rising as the global population grows. In contrast, fish stock is declining due to human activity, environmental changes and overfishing. Fish monitoring provides valuable support data for effective fishery management and ecosystem conservation. The common monitoring methods are based on manual sampling, which is time-consuming, laborious and intrusive. Imaging sonar is a hydroacoustic system that produces acoustic images similar to optical images by transmitting and receiving sound waves, allowing for in situ monitoring of fish non-intrusively in the dark and turbid water environments where optical cameras are limited. In the last decade, imaging sonar, especially high frequency multibeam forward-looking sonar and side-scan sonar, has been widely used in fish monitoring. We reviewed the literature from the previous decade on the use of these two types of imaging sonar in fish species identification, abundance estimation, length measurement and behaviour analysis, as well as the sonar imagery processing concerning fish. The review results show that these imaging sonars are efficient and effective tools for fish monitoring in complex environments. The challenges include(1) the recognition of small fish forming dense aggregations; (2) species identification, which limits their use in species-specific studies; (3) time-consuming massive data processing. Therefore, advanced algorithms for sonar imagery processing and integrations with other sampling technologies are needed for future development.

Automatic detection, identification and counting of anguilliform fish using in situ acoustic camera data: development of a cross-camera morphological analysis approach

“…In acoustic camera videos, the horizontal dimension of pixels, or cross-range resolution (6) depends on the detection range, which influences an operator’s visualization of fish (43) and may decrease measurement accuracy (44,45). Our results for the PLN-ARIS dataset highlight the method’s robust performances for eels 4-9 m from the camera.…”

“…Analysis of acoustic video by an operator is a time-consuming process that requires a degree of expertise to distinguish fish from other objects and to identify fish species. Multiple automatic or semiautomatic methods have been developed to detect and describe fish using acoustic camera datasets, listed and described in the review of (6). Among the studies quoted by (6), a few authors focused on the distinction of species of interest, such as anguilliform fish, from other species (12)(13)(14).…”

“…Multiple automatic or semiautomatic methods have been developed to detect and describe fish using acoustic camera datasets, listed and described in the review of (6). Among the studies quoted by (6), a few authors focused on the distinction of species of interest, such as anguilliform fish, from other species (12)(13)(14). Indeed, an operator can easily distinguish the particular body shape and swimming undulation of anguilliform fish from those of most other fish species (15)(16)(17)(18).…”

“…Many technical improvements have been made over time (4), among which acoustic cameras (i.e. imaging sonar) are key (5,6). Due to their multiple beams and high frequency, these devices can project the echoes that they detect in a large volume, as 2-dimensional images.…”

“…Recently, in addition to the most commonly used models of acoustic camera – DIDSON and ARIS (Sound Metrics Corp., Bellevue, WA, USA) – new and less expensive models have become available that can scan a larger volume but have lower resolution, such as BlueView (Teledyne Technologies Inc., Thousand Oaks, CA, USA) and Oculus (Ulverston, Cumbria, United Kingdom). Based on these advantages, acoustic cameras are useful for studying long-term migration dynamics in rivers, assessing information on stock and population, and providing new insights for fishconservation policies (6).…”