Working Group on Acoustic and Egg Surveys for Sardine and Anchovy in ICES Areas 7, 8 and 9 (WGACEGG)

Type Scientific report
Date 2018
Language English
Ref. ICES CM 2017/EOSG:04
Other localization http://ices.dk/sites/pub/Publication%20Reports/Expert%20Group%20Report/SSGIEOM/2017/WGACEGG/WGACEGG.pdf
Author(s) ICES
Contributor(s) Doray MathieuORCID, Duhamel Erwan
Abstract

The 2017 meeting of the Working Group on Acoustic and Egg Surveys for Sardine and Anchovy in ICES Areas 7, 8 and 9 (WGACEGG) was held in Cadiz, Spain on 13- 17/11/2017. During this meeting, sardine and anchovy biomass indices derived from acoustic and Daily Egg Production Method (DEPM) surveys in ICES areas 8 and 9 have been evaluated and compared. Those indices have been provided to the ad-hoc ICES WGHANSA stock assessment group, to serve as fishery-independent input for analytical assessment purposes. DEPM and acoustic indices were derived based on data collected using independent methods. They have been compared to assess the presence of potential bias in one or the other biomass index, to improve the precision of fish stock biomass estimates. The working group has developed new methodologies to assess and report on the reliability of individual survey indices, and compare DEPM and acoustic indices. Maps of anchovy mean weight derived from acoustic data were for instance used as a proxy of fish fecundity maps and compared to maps of eggs abundance collected during the PELGAS survey in the Bay of Biscay. This approach opens up perspectives to construct a quality index of the anchovy biomass estimates used in analytical stock assessment, based on the differences between maps derived from acoustic and DEPM data. The methodologies proposed for improving the assessment and reporting of survey indices reliability, and for comparing acoustic and DEPM data presented during the meeting will be refined and further tested during the 2018 meeting. The WACEGG group has updated its database of standard gridded maps covering the European Atlantic area and informing on the spatial dynamics of various parameters collected during the surveys coordinated under the auspices of the group (fish acoustic densities, anchovy and sardine egg abundance, surface temperature and salinity, seabird and cetaceans, etc). These standard maps can be used to compute global indices describing the state of the European Atlantic pelagic ecosystem in spring and autumn. New methodologies for the analysis of time-series of maps of ecosystem indicators have been presented during the meeting. They will be applied to the WGACEGG gridded maps database before the next meeting, to quantitatively assess the spatial and temporal distribution of anchovy and sardine in European Atlantic waters over the last 15 years, and further define their habitats. The timing and spatial coverage of DEPM and acoustic surveys that will be conducted by group members in 2018 have been reviewed and discussed during the meeting to optimise the monitoring of anchovy and sardine populations and their pelagic environment in the European Atlantic area. A procedure for combining anchovy biomass estimates derived from different survey data and methodologies in the ICES area 9 has been proposed by the group. A manual describing the protocols used during the DEPM surveys coordinated by the WGACEGG group has been written during the meeting. It will be submitted to ICES as a contribution to the Series of ICES Survey Protocols (SISP). Methodologies used within the WGACEGG group for collecting and analysing acoustic data have been reviewed and summarized, with the objective of writing a SISP manual of WGACEGG acoustic surveys during the 2018 meeting. Methodological developments on the estimation of mesopelagic fish biomass, the characterisation of juvenile anchovy individual backscatter, and on the assessment of fish biomass distributed near the sea surface (0-10m depth) have been discussed during the fisheries acoustics session. Methodological developments on how does the number of stages affect daily egg production and mortality rates estimates within the DEPM for anchovy and sardine in the Bay of Biscay and the vertical distribution of anchovy eggs based on multinet sampling in the Gulf of Cadiz were present and discussed during the DEPM session. Moreover, the work plan for exploring the differences between total daily egg production and mortality rates derived from CUFES and PairoVET was reviewed during the session.

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