Working Group on Fisheries Acoustics, Science and Technology (WGFAST)

Abstract

s for all work presented in 2016 are found in Annex 5. Applications of acoustic methods to characterize ecosystems This session highlighted the wide range of applications of acoustics to characterize a fast growing list of ecosystem characteristics and features. Acoustic methods are being used to assess and develop models of krill distribution, investigate soundscattering layers, refine our definition and comprehension of pelagic habitats (through tools like the Profiling Lagrangian Acoustic, Optical System), and help construct a better understanding of oceanic features such as frontal zones. A wide range of acoustic tools and methods were displayed in this session as well, from the use of conventional commercial echosounders to assess the distribution of key fish species in trap fisheries, multibeam system to assess the distribution of fish assemblages around gas platforms, upward-looking moored echosounder to monitor juvenile salmon migration at sea, and the use of broadband technology to improve fish species and size discrimination with the goals of minimizing overfishing and bycatch. As the community is striving to use acoustics to its full potential in ecosystem assessment, new ways of using and integrating existing data are also being explored. This included for example the use of night-time data in typical daytime anchovy surveys, the use of historical surveys defined for one species (Atlantic herring) to assess another (Bluefin tuna), and comparing biomass estimates derived from different sources such as acoustic and bottom-trawl surveys. The complexity and wealth of information in acoustic data can present analytical challenges, and efforts are being made in testing the ability of models to measure and detect change (an important aspect for environmental assessment and ecological research), and in the development of synthetizing tools for ocean observation and monitoring, through initiative like the Nekton Interactive Monitoring System (NIMS). All of these presentations were great examples of how acoustics has now become an important and valuable tool in ecosystem research, and will continue to expand as new vessels equipped with a suite of broadband, multibeam, and omni-sonar systems (such as the RV Tamgu-21 highlighted by South Korea) will take on the world oceans. A common challenge to all of these ecological applications is the verification of target animal, the so-called ground-truthing. All sampling tools have biases, and truly integrated ecosystem science need to use a combination of methods and tools. It is generally agreed that several sampling tools independent of each other are desired, but in some cases tools are used to understand and assess the bias and constraints of another tool (an example of this is the combination of optical systems within trawlnets). There is undoubtedly a need for more research into the selectivity and organisms reactions to the various sampling tools used in science, and the development of alterICES WGFAST REPORT 2016 | 7 native methods when and where conventional tools cannot be use, such as in untrawlable areas. Mixed aggregations of species remain a particular challenge. Even when sampled with nets using multiple closing codend, some aggregations are composed of several species that are integrated together in samples (e.g. mesopelagic fish communities). This is where progress in broadband/wideband technologies and processing could really make a difference.