Publication Abstract

28/05/25: Annex 3 supplemented with the PELACUS 2024 survey summary sheet

WGACEGG coordinates acoustic and egg surveys of several pelagic stocks in the Celtic Seas, Bay of Biscay and Iberian coast (ICES areas 6-9). Results from the surveys were discussed with members of WGHANSA and methods were considered reliable. The biomass of anchovy was low in area 7 of the Celtic Seas, high in the Bay of Biscay (area 8) and of medium biomass in the Iberian coast (area 9). In areas 7-9, the biomass estimates of sardine were relatively high, while the biomasses of horse mackerel and mackerel were generally low. Sprat biomass decreased in area 8 and increased in the English Channel (ICES divisions 7de). The biomass of boarfish stocks were reported to be intermediate in areas 6 and 7, while the biomass of her-ring in the Celtic Seas requires further investigation.

Methods were investigated across a range of case-studies including an investigation of poten-tial bias through a comparison of indices from acoustic and Daily Egg Production Method (DEPM) methods for anchovy and sardine in area 8, the Bay of Biscay. No sign of bias was found in 2024 acoustic and egg indices. The suitability of Continuous Underway Fish Egg Sampler (CUFES) sampling data for anchovy and sardine egg production estimates in areas 8 and 9 was assessed using the approach developed by Ifremer. Additional studies considered methods to correct distortion in multibeam sonar data, ways to reduce the uncertainty in echo trace classifiers and the use of a glider with a surface drone for acoustic monitoring. Target strength estimation of Atlantic bluefin tuna, anchovy and sardine were investigated. Ecological studies addressed the spatio-temporal variability in anchovy and sardine eggs within the Bay of Biscay and English Channel and the seasonal and interannual dynamics of common dolphin energy seascapes, based on epipelagic prey distribution in the Bay of Biscay.

The group updated gridded maps in ICES areas 6-9 for both biological and environmental variables and developed spatio-temporal models of the estimated biomass distribution of sardine and anchovy in the Bay of Biscay. The database of the gridded data-product will be published in a public repository during 2025. A planned workshop discussing the use of im-age recognition techniques to characterise the distribution of mesozooplankton communities was delayed to 2025. The ICES Techniques in Marine Environmental Sciences reporting on DEPM surveys series will be published in early 2025.

Guillermo Boyra; Jose Canseco; Pablo Carrera; Paz Díaz; Rosario Domínguez; Mathieu Doray; Erwan Duhamel; Martin Huret; Paz Jiménez; Anxo Lago; Maria Manuel Angélico; Ana Moreno; Ciaran O'Donnell; Fernando Ramos; Silvia Rodríguez; María Santos; Beatriz Sobradillo; Jeroen Van Der Kooij*

Working Group on Acoustic and Egg Surveys for small pelagic fish in Northeast Atlantic (WGACEGG; outputs from 2024 meeting)