The Pélagiques Gascogne (PELGAS) integrated survey has been developed by a multidisciplinary team of Ifremer and La Rochelle University scientists since 2000, joined by commercial fishermen in 2007. Its initial focus was to assess the biomass and predict the recruitment success of anchovy in the Bay of Biscay in spring. Taking advantage of the space and versatility of R/V Thalassa II, sampling has been progressively extended to other ecosystem components. PELGAS therefore further developed the second objective of monitoring and studying the dynamic and diverse Biscay pelagic ecosystem in springtime. The PELGAS survey model has allowed for the establishment of a long-term time-series of spatially-explicit data of the Bay of Biscay pelagic ecosystem since the year 2000. Main sampled components of the targeted ecosystem are: hydrology, phytoplankton, mesozooplankton, fish and megafauna. The survey now provides two main ecosystem products: standard raster maps of ecosystem parameters, and a time series dataset of indicators of the Bay of Biscay pelagic ecosystem state. They are used to inform fish stock and ecosystem-based management, and support ecosystem research. The present paper introduces the PELGAS survey, as a practical example of an integrated, vessel-based, ecosystem survey. The evolution of the PELGAS scientific team and sampling protocols are presented and analysed, to outline factors crucial to the success of the survey. Data and results derived from PELGAS are reviewed, to exemplify scientific questions that can be tackled by integrated ecosystem survey data. Advantages and challenges of the survey are discussed and put into the context of marine ecosystem surveys in the European Marine Strategy Framework Directive and the Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. Common Fisheries Policy. Highlights ► The PELGAS integrated survey conducted since 2000 in spring in the Bay of Biscay is presented. ► PELGAS objectives have switched from the study of the anchovy stock status to ecosystem monitoring. ► Spatially-explicit data have been collected of the main pelagic ecosystem components since 2000. ► Multidisciplinary collaborative working and enough vessel space were critical success factors. ► Finding relevant common scales is essential to analyse ecosystem data within or across compartments.

Knowledge of the pelagic vertical distribution of fish eggs is central for several aspects of fisheries science including fisheries recruitment and egg production studies. In modelling egg vertical distributions, variation in fish egg density is an important issue. Though variation in egg density between individual eggs has been reported, evidence for significant spatial variation in egg density is novel. The present study provides evidence that egg density of anchovy (Engraulis encrasicolus) varies spatially across spawning sites in the Bay of Biscay, depending on the regional scale variation in sea water properties due to river discharge. We measured the density of the eggs using a density gradient column at 17 stations in 2005 and 2006 as well as their diameter. At station, the variability in the individual egg density was statistically distributed according to a Gaussian probability function. Significant variation in the mean egg density was observed across stations. Mean egg density displayed a significant correlation with sea surface salinity. Results are discussed in light of the mechanisms determining the egg density.

SUMMARY:The spatial pattern in hydro-plankton and fish distributions and their relationship were analysed based on the spring 2000 fisheries acoustic survey. The importance of this survey was that it was a multi-disciplinary platform which collected an extensive set of parameters in the hydro-plankton leading to a potentially finer description of hydro-plankton conditions and fish habitats. More than 50 variables were measured on a grid of stations, in four compartments of the ecosystem: hydrology, nutrients, primary producers and meso-zooplankton. First, a joint analysis of all hydro-plankton compartments was performed using multiple factor analysis (MFA). The method was used to estimate a compromise factorial space common to all compartments in which the stations were grouped by hierarchical clustering. The groups were represented spatially and a strong spatial pattern was evidenced. The fish and their spawned eggs were sampled along transect lines using acoustics and CUFES (continuous underway fish egg samplers). The distribution of the fish and their eggs was analysed in relation to the hydro-plankton groups of stations and difference in fish density across hydro-plankton conditions was tested by a pair-wise multiple comparison procedure. Anchovy was associated with a lesser number of hydro-plankton conditions than sardine. Eggs of both species were also associated with a lesser number of conditions than the fish. Finally, the gain provided by using the extensive set of hydro-plankton parameters for mapping large-scale hydro-plankton conditions was analysed in comparison with the situation in which a small set of parameters was available. The extensive set of parameters allowed more hydro-plankton conditions to be identified but only in the coastal area and not on the shelf. Size fractionated chlorophyll was determinant for tracking river plume hydro-plankton condition. However, the fish did not respond to the variety of the coastal hydro-plankton conditions. Keywords: spatial pattern, multiple factor analysis, habitats, hydro-plankton, fish-environment relationship. RESUMEN: CARACTERÍSTICAS HIDRO-PLANCTÓNICAS Y SU RELACIÓN CON LAS DISTRIBUCIONES DE SARDINA Y ANCHOA EN LAPLATAFORMA FRANCESA DEL GOLFO DE VIZCAYA. -Este artículo analiza la relación espacial entre los peces pelágicos y su medio ambiente utilizando datos de la campaña acústica francesa del año 2000. Esta campaña fue multidisciplinaria y permitió la colección de una lista extensa de parámetro en el hidro-plancton. Mas de 50 variables fueron muestreadas sobre la misma red de estaciones. Estas variables se agrupan en cuatro compartimientos del ecosistema: hidrología, nutrientes y materia en suspensión, bacterias y fitoplancton, mesozooplancton. En primer lugar se hizo una análisis conjunto a todas las variables reagrupadas en los cuatros compartimientos aplicando el método MFA (Análisis Factorial Múltiple). El método permitió estimar el espacio factorial común a todos los compartimientos en el que se hizo un agrupamiento de las estaciones. Los grup...

In this paper we present the ZooCAM, a system designed to digitize and analyse on board large volume samples of preserved and living metazooplankton (i.e. multicellular zooplankton) and fish eggs > 300 µm ESD. The ZooCAM has been specifically designed to overcome the difficulties to analyse zooplankton and fish eggs in the framework of the PELGAS survey, and provide high frequency data. The ZooCAM fish eggs counts were comparable to those done with a dissecting microscope. The ZooCAM enabled the accurate prediction and fast on board validation of staged anchovy and sardine eggs in almost real time after collection. A comparison with the ZooScan, on a more complex zooplanktonic community, provided encouraging results on the agreement between the 2 instruments. ZooCAM and ZooScan enabled the identification of similar communities and produced similar total zooplankton abundances, size distributions, and size spectra slopes, when tested on the same samples. However these results need to be further refined due to the small number of samples used to compare the two instruments. The main ZooCAM drawback resides in a slight but sensible underestimation of abundances and sizes, and therefore individual and community biovolumes. The ZooCAM have been successfully deployed over 4 years, on numerous surveys without suffering any major failure. When used in line with the CUFES it provided high resolution maps of staged fish eggs and zooplanktonic functional groups. Hence the ZooCAM is an appropriate tool for the development of on board, high frequency, high spatial coverage zooplanktonic and ecosystemic studies. Highlights ► The ZooCAM is a new inflow imaging system for fast onboard counting, sizing and classification of fish eggs and metazooplankton. ► The ZooCAM has been used on-board for 4 years without suffering any failure and enabled the analysis ∼10,000 samples so far (CUFES, WP2 and other plankton nets). ► The ZooCAM provided staged fish eggs counts that were equivalent to those traditionally done by microscopic examination. These data were used for 2016 and 2017 anchovy and sardine stocks estimations in the Bay of Biscay (DEPM method) ► The ZooCAM enable the real time, on-board, imaging of complex communities zooplankton samples and provide results comparable to on-land, well established counterpart, the ZooScan. ► The ZooCAM is a valuable tool to improve zooplanktonic studies, in term of spatial coverage and temporal frequency, to perform ecosystemic studies.

Petitgas, P., Goarant, A., Massé, J., and Bourriau, P. 2009. Combining acoustic and CUFES data for the quality control of fish-stock survey estimates. – ICES Journal of Marine Science, 66: 1384–1390. Fish behaviour may cause bias in the acoustic estimates of fish stocks, which are difficult to assess using acoustic data alone. In contrast, fish eggs are passive particles that can be sampled with little avoidance. The combination of CUFES (continuous, underway, fish-egg sampler) data with acoustic sampling has the potential to cross-validate methods and address the question of relative bias. For anchovy in the Bay of Biscay, a CUFES has been used in conjunction with acoustics along the transect lines of IFREMER’s spring acoustic survey since 2001. Subsurface CUFES egg concentrations were converted to vertically integrated egg abundances using a biophysical model of egg vertical distribution. Then, a procedure similar to the daily egg production method (DEPM) was applied to map an index of daily egg production. Maps of fish abundance and egg production were combined to derive a second index of daily specific fecundity over the survey area, which served as a quality-control indicator of the survey estimate. Over the series of surveys analysed, the quality-control indicator provided two warnings and in both cases the reasons for these were identified.