Research progress in application of echo-sounder buoys in tuna purse seine fishery

Echo-sounder buoys can provide accurate geographic positioning of drifting fish aggregating devices (DFADs) and estimates of tuna stock biomass for tuna purse seine fisheries remotely and on a continuous basis, effectively reducing the "carbon footprint" of the purse seine fleet in searching for fish and fleet operating costs, thereby increasing the success of the fleet currently, DFADs-based tuna purse seine catches account for 54% of the total tuna purse seine fishery catch. In addition to its commercial application, the echosounder buoy has the potential to serve as a scientific platform for observing pelagic biodiversity, providing data to describe pelagic fish activity patterns for scientific research, helping to improve understanding of the accompanying behavior of DFADs, as well as the potential to develop an abundance index for tuna stock assessment independent of fisheries data. This paper firstly introduces the definition, types and structures, ecological impact and related management measures of DFADs, as well as the evolution, categories and data structure of echo-sounder buoys. The application of echo-sounder buoys in tuna purse seine fishery was reviewed from the aspects of: biomass assessment, fish association behavior and ecological impact posed by DFADs. Among them, tuna floating objects associated schools are analyzed and discussed in terms of the rapidity and persistence of tuna aggregation of DFADs, while the colonization time is the main indicator of the rapidity of tuna aggregation, and the continuous residence time and colonization rate are the key indicators of the persistence of tuna aggregation. The ecological impact assessment of DFADs mainly discusses the impact of DFADs stranding events, the number of DFADs deployment and DFADs bycatch on the marine ecological environment. This paper prospects the echo-sounder buoys on technical support in the future to reduce the target species and species, the development trend of the juvenile mortality from fishery resources and the sustainable management and marine biodiversity protection discussed combining fishery resources assessment data buoy observation data and to explore the climate change and human activities on the marine ecological influence the huge potential of the ecological system.