ICES. 2020. Working Group on Acoustic and Egg Surveys for Sardine and Anchovy in ICES areas 7, 8 and 9

he Working Group on Acoustic and Egg Surveys (WGACEGG) coordinates pelagic surveys for a number of stocks and provides monitoring for the two major sardine and anchovy stocks in ICES areas 6, 7, 8, and 9. The group evaluated small pelagic fish biomass indices derived from acoustic and Daily Egg Production Method (DEPM) surveys in ICES areas 6, 7, 8 and 9. These indices have been provided to the ICES Working Group on Southern Horse Mackerel, Anchovy and Sardine (WGHANSA), the Working Group on Widely Distributed Stocks (WGWIDE) and the Herring Assessment Working Group for the Area South of 62ºN (HAWG) 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. Acoustic- and DEPM-derived biomass indices from quasi-synoptic surveys conducted in the Bay of Biscay in spring were compared, to assess the presence of potential bias and to improve the precision of fish stock biomass estimates. The DEPM-based anchovy biomass index was 22% higher than the acoustic index in 2019. Unusual concentrations of anchovy in Eastern Cantabrian Sea, an area not covered by the acoustic survey, and the presence near the sea surface of actively spawning individuals possibly under-sampled by acoustics in central Bay of Bay had been postulated as potential causes of this discrepancy. No significant difference was found between sardine biomass indices derived from DEPM and acoustics in 2019. The group has updated its database of standard gridded maps covering the European Atlantic area. This initiative continues to inform 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). Results of an analysis of the time series of gridded maps (anchovy and sardine acoustic density, surface salinity and temperature) showed quantitative changes in the spatial and temporal distribution of anchovy and sardine over the last 15 years, and further define their habitats in European Atlantic waters in spring. The timing and spatial coverage of DEPM and acoustic surveys that will be conducted by group members in 2020 were planned to optimise the monitoring of anchovy and sardine populations and their pelagic environment in the European Atlantic area. The synoptic nature of the survey components has been assessed for each target species. A manual describing the protocols used during the DEPM surveys coordinated by the WGACEGG group was reviewed, and writing of a manual of WGACEGG acoustic surveys continued. Both manuals will be available in 2020. The final results of the 2017 sardine DEPM assessment were endorsed by the group

Anchovy egg mortality in the Gulf of Cadiz (SW Spain) and its application to Egg Production Estimation

Fish egg mortality is relevant for ecological studies and also required to estimate egg production by the Daily Egg Production Method (DEPM), with a consequent effect on the Spawning Stock Biomass (SSB) estimation. An external mortality model for anchovy (Engraulis encrasicolus) eggs in the Gulf of Cadiz is estimated in order to overcome the high variability introduced by yearly estimates for mortality and therefore improve the egg production estimation. To establish the model, extra data on abundances by development stage were obtained by revising all the data from several research surveys that included plankton sampling, carried out in waters of the Gulf of Cadiz during 2005-2014. A total of 31119 anchovy eggs were classified into the 11 stages described by Moser and Ahlstrom, 1985. For each sample the information on water temperature, sampling depth and location was also recovered. The process to estimate mortality and egg production include 3 steps: 1) estimation of daily cohort abundance by age; 2) mortality estimation considering variables such as temperature and geographical strata; 3) P0 calculation using the mortality values obtained in step 2. The results show a clear effect of temperature in the egg mortality rate and also a spatial pattern in its distribution which are then reflected in the egg production estimate

Sardine spawning biomass estimation (ICES areas IXa and VIIIc) through the application of DEPM in 2014

Surveys for the application of the DEPM to estimate the sardine spawning biomass within the Atlanto-Iberian stock area are conducted every three years by IPMA (Instituto Portugués do Mar e da Atmosfera, Portugal) and IEO (Instituto Español de Oceanografía, Spain). DEPM surveys consisted of ichthyoplankton, adults and hydrographic sampling and are internationally coordinated and planned within the framework of ICES WGACEGG.This working document provides a description of the surveys, laboratory analyses and estimation procedures used to obtain egg and preliminary adults parameters for the 2014 DEPM application to the Atlanto-Iberian sardine stock. A preliminary estimation of spawning stock biomass (SSB) is also presented

Atlanto Iberian sardine spawning stock biomass during 2014 DEPM survey (ICES areas IXa and VIIIc)

The present document includes an update on the results from the Atlanto Iberian sardine 2014 DEPM survey submitted to the WGACEGG in November 2014. For the preliminary SSB estimates presented at the 2014 meeting, an average spawning fraction value (using the whole series data) was considered for the southern (Algarve and Cadiz Bay) and western strata (western Portugal) since the information collected during the 2014 campaign in those areas was not fully processed. Detailed sampling and laboratorial methodology and survey description including environmental characterization and sampling effort can be found in the 2014 WGACEGG repor