The improved knowledge of the pelagic ecosystem of the Bay of Biscay resulting from PELGAS results from the accumulation of observations during the series of cruises. We will therefore present the main results obtained by theme, rather than by campaign.

1. Hydrology of the Bay of Biscay

The in situ measurements of the hydrology of the Bay of Biscay carried out during PELGAS have made it possible to develop a method for mapping water masses which makes it possible to identify ¿hydrological landscapes¿ (Planque et al. 2006). The spatio-temporal dynamics of these hydrological landscapes were analyzed from 1990 to 2003 (Villalobos 2008) and on a temperature and salinity climatology (Bobyclim) based in particular on CTD data from PELGAS (Gailhard-Rocher et al. 2012). This last study produced a map of hydrological landscapes with similar seasonal dynamics.

Hydrological landscapes have been proposed to be included in the list of hydrological indices (item 'pelagic habitats') of the good state of European marine ecosystems (Gailhard-Rocher et al. 2012).

Hydrological data from CTD profiles, hull sensors and instrumented buoys released during the PELGAS cruise have contributed to studying surface circulation (Charria et al. 2013; Reverdin et al. 2013) and toxic algal blooms ( Batifoulier et al. 2013), as well as to validate the outputs of the hydrodynamic model MARS3D (Lazure et al. 2009), then of its ecosystemic extension ECOMARS (Huret et al. 2013) in the Bay of Biscay. These models now make it possible to situate the hydrological situation observed during PELGAS in the seasonal dynamics of water masses. They also provide data to detect the long-term hydrological trends in which the campaigns are part, by means of a statistical monitoring system of hydrobiological indicators from ECOMARS (Woillez et al. 2010).

A study aimed at placing the annual PELGAS campaigns in the seasonal cycle of the ecosystem was carried out, in order to define the "ecological dates" on which each observation of each annual campaign had taken place. The results showed that the date and duration of the campaign could lead to biases in the observations of certain rapidly changing parameters, in particular the surface temperature. The use of the ¿ecological dates¿ of the campaigns instead of their calendar dates also made it possible to refine the description of the phenology and the spatial distribution of the spawning of anchovies and sardines (Huret et al. 2018).

2. Plankton communities

The hydrobiological data collected during PELGAS helped to highlight the influence of the Gironde plume on primary production in the Bay of Biscay (Labry et al. 2002) and in particular the presence of an early bloom of microphytoplankton in winter ( Labry et al. 2001). The PELGAS data made it possible to map the spring phyto and zooplankton communities of the Bay of Biscay on a larger scale (Petitgas et al. 2006). Integrated with the data collected during other coordinated campaigns, the PELGAS data made it possible to show that the dynamics of the planktonic trophic chains of the Bay of Biscay was similar to that of the other temperate oceans, with the exception of the presence of the microphytoplankton bloom in winter and a phosphate limitation (Marquis et al. 2007).

With a view to automating sampling and therefore increasing the volume of observed zooplankton habitats, optical (LOPC) and acoustic (hull sounders and vertical profiler) sampling was developed. A mapping of the size spectrum of zooplankton in the Bay of Biscay observed during the PELGAS cruises was carried out by combining data from LOPC and planktonic fishing at WP2 (Vandromme et al. 2014). A thesis started in 2011 aims to clarify the first attempts at acoustic characterization of the acoustic diffusing layers (Trenkel and Berger 2010) by combining the multifrequency acoustic data acquired continuously along the radials and the hydro-biological data collected punctually in station during PELGAS , in order to characterize the meso-zooplankton layers of the Bay of Biscay on a mesoscale. Pelagic particles from the mouth of the Gironde to the shores were characterized for this purpose on a fine scale using multiple sensors (acoustic, optical, nets, etc.) during PELGAS 2012 and 2013 (Doray et al. 2012).

The development by Ifremer during the campaign of a meso-zooplankton flow imager, the Zoocam (Colas et al. 2018), made it possible to re-analyze with a standard methodology all the zooplankton samples collected with the WP2 net since 2004 (Grandrémy et al. 2023). The re-analysis of these historical data made it possible to map the zooplankton communities in the Bay of Biscay in the spring, and to highlight that the average spatial patterns of zooplankton are influenced by the bottom up forcing of hydrology and a control top-down of small pelagic fish (Grandrémy et al. 2023).

3. Population dynamics of anchovies and sardines in the Bay of Biscay, stock management

     3.1. Abundance assessments and stock management

PELGAS produces each year an acoustic abundance index of the groups of anchovies, sardines, sprats and horse mackerel observed during the mission. The campaign also provides biomass by size and age classes for anchovies and sardines. The accuracy of these abundance indices is assessed using survey data and the assessment method (Doray et al. 2010) is improved based on studies on the individual acoustic reflectivity of small pelagic fish (Doray et al. al. 2011) multi-frequency classification of acoustic targets (Trenkel and Berger 2010) or attribution of acoustic fish densities to identification trawls (Petitgas et al. 2003). The abundance indices of anchovies and sardines in the Bay of Biscay from PELGAS are combined with those provided by the BIOMAN campaign of AZTI, which assesses the same stocks for the same period from spawning data. A method combining the abundance indices from PELGAS and BIOMAN has been proposed, in order to judge and detect possible biases in the estimates and to improve their reliability (Petitgas et al. 2009). Indices from acoustics and eggs are combined in the population dynamics model BBM, within the CIEM WGHANSA working group, in order to produce an assessment of anchovy biomass in the Bay of Biscay. The group then makes management recommendations to the European Commission, which sets the level of the annual TAC. The abundance of the anchovy stock in the Bay of Biscay has always shown great variability, linked to significant fluctuations in recruitment (individuals aged one year).

Recruitment to the anchovy stock has been low since 2002, with a historic low in 2005, which led to the closure of the fishery. The fishery was reopened in 2010, following the good recruitments recorded by the PELGAS and BIOMAN campaigns. A sardine abundance index present in the Bay of Biscay in spring is also assessed from PELGAS data, but the stock is not subject to TAC management.

Sardine biomass is also highly variable from one year to the next. Part of this variability must come from the fact that the spring sardine migrations (probably from the Celtic Sea or further afield) did not end at the time of the PELGAS cruise. The mission therefore does not necessarily observe the entire stock of sardines each year. Nevertheless, the cohorts can be followed over the years, which suggests that the PELGAS campaign samples enough sardines in the Bay of Biscay in the spring to capture the main trends in its population dynamics.

3.2. Contributions to spatialized stock management

Due to the homogeneity and good resolution of the spatial coverage of the Bay of Biscay that it achieves, the PELGAS cruise makes it possible to finely characterize the spatial patterns of small pelagic fish stocks. These spatial patterns have been analyzed in order to advance the spatialized management of small pelagic fish stocks.

Constructed from trawl data from acoustic campaigns since 1983, a spatialized model of anchovy population dynamics showed that it depended mainly on the fertility of 1-year-old fish present in an area located in front of the Gironde estuary (Petitgas and Vaz 2005). This ¿essential¿ spawning habitat has been precisely mapped, and a spatialized management procedure for the anchovy fishery, an alternative to the current management, has been proposed to the authorities involved in the management of the stock.

The impact on the anchovy population and fishing activity of spatialized management scenarios, including a seasonal closure of fishing in the Gironde estuary, was tested by simulation with the ISIS spatialized model. The results of this model, largely parameterized with data from PELGAS, confirmed the importance of recruitment in the dynamics of the Bay of Biscay anchovy population, without highlighting any significant effect of the closure of the area. Gironde (Lehuta et al. 2010).

     3.3. Determinism of anchovy recruitment

Due to the influence of recruitment on the dynamics of the anchovy population, the PELGAS cruise served as a privileged platform for the study of the determinism of the recruitment of this species.

Larval drift simulations from buoy drift data released during PELGAS and MARS3D model outputs were combined with growths of anchovy larvae and juveniles derived from otoliths collected during PELGAS. This combination has made it possible to construct an individual-centered (IBM) biophysical model of growth and survival of anchovy larvae and juveniles (Allain et al. 2003; Allain 2004). This model was then used to predict the recruitment index of the anchovy population from 3 years of MARS3D hydrological forecasts (Allain et al. 2007b) and to investigate the influence of environmental conditions and the dynamics of oviposition on larval survival (Allain et al. 2007a).

The spawning data, vertical distributions of eggs and larvae, energy-density and isotopes from PELGAS then contributed to defining the hypotheses for more realistic larval drift simulations, conducted with the new ECOMARS model. These simulations carried out over a long period (1996-2007) made it possible to determine the factors most influencing the dispersal of larvae at different spatial and temporal scales. The factors tested were the vertical movements of the larvae, the duration of the drift, the spawning dynamics and the seasonal and inter-annual hydrological variability (Huret et al. 2010b). The same IBM model was used to test the effect of climate scenarios on the dispersal of anchovy larvae (Huret et al., 2009, Lett et al., 2010).

Limiting factors of anchovy recruitment, including both hydrological indices from ECOMARS and indices describing adult spawning, have been identified annually at each stage of the anchovy life cycle. The combined analysis of factors limiting recruitment from 1986 to 2009 confirms the importance of the larval period, which is often limiting. Recruitment limiting factors change over the course of the series, confirming the multiple nature of anchovy recruitment determinism (Petitgas et al. 2011b).

Finally, an IBM model of the whole life cycle was developed, based on PELGAS data on eggs, larvae and adults of anchovies as well as data on zooplankton and predators contribute.

4. Spatial distribution, habitats and life cycles of small pelagic fish in the Bay of Biscay

    4.1. Spatial distribution

The georeferenced acoustic, halieutic and hydrobiological data collected during PELGAS made it possible to model the spatial distribution of small pelagic fish in the Bay of Biscay at various stages of development.

Systematic monitoring of the spatial distribution of anchovy and sardine eggs during PELGAS has shown that anchovy spawning was more fragmented in the 2000s than in the 1960s-70s and that spawning now extended further north (Bellier et al. 2007). Nested aggregative structures resulting from the expression of the gregarious behavior of small adult pelagic fish species in the face of environmental forcing have been demonstrated at several scales (shoal, cluster of schools, cluster of clusters) (Petitgas 2003). ¿Acoustic populations¿, grouping together adults of species whose schools have similar characteristics on the ¿acoustic images¿ have been defined (Petitgas et al. 2003) and their spatio-temporal dynamics studied from data collected from 1990 to 2003 (Villalobos 2008)

The mean distribution of small adult pelagic fish in the Bay of Biscay has also been mapped by size class and species from PELGAS data (Certain et al. 2011, Doray et a. 2018b).

     4.2. Habitats

The spatial patterns of small pelagic fish in the Bay of Biscay observed during PELGAS have been related to environmental parameters, in order to define the habitats of these species.

The probability of egg presence was modeled according to hydrological parameters collected during PELGAS, in order to define the influence of environmental conditions on the distribution of potential spawning areas. This study showed that potential anchovy spawning habitats were essentially determined by a reduced set of hydrological indices (bottom temperature, surface temperature and depth of the mixed layer), and that these parameters could be used to predict the temporal dynamics of potential spawning habitats from the outputs of the MARS3D model (Planque et al. 2007).

The spatio-temporal dynamics of the realized habitats of anchovy adults, i.e. the areas where anchovies were actually observed, was modeled as a sum of orthogonal functions (EOF) from PELGAS data (Petitgas 2008). The existence of statistical relationships between these EOFs and the overall abundance of the population and environmental indices has been demonstrated (Petitgas et al. 2014) and exploited in order to simulate the habitats that the Bay of Biscay anchovy would occupy in response the effects of climate change (Petitgas et al. 2009b).

A kriging method for mapping fish size histograms was developed using fishing data from PELGAS (Petitgas et al. 2011a). Applied to anchovies from the Bay of Biscay, it showed that large anchovies (>16cm) dominated (>60% of numbers) in the size distributions of the southern Gulf, while smaller anchovies (<12cm) systematically shared their habitats with larger anchovies.

A study was carried out to define time-stable small pelagic fish communities and their characteristic distribution areas, based on data collected during PELGAS (2000-2015) (Doray et al. 2018a). The comparison of the recurrent distribution patterns of the fish communities and their hydrological environment made it possible to define the physico-chemical characteristics of their habitats in the spring.

Length, growth and energy-density data collected during PELGAS (Dubreuil and Petitgas 2009; Gatti et al. 2018) were used to calibrate an anchovy bioenergetic model (Pecquerie et al. 2009; Gatti et al. 2017 ).and sardine (Gatti et al. 2017) from the Bay of Biscay. This model makes it possible to predict the potential habitats of the anchovy on a physiological basis (Pecquerie et al. 2009), i.e. and to explore its reproductive migrations, from outputs of the ECOMARS model (Politikos et al. 2015).

4.3. Life cycles of small pelagic fish in the Bay of Biscay

PELGAS also served as a platform to collect data on the genetic structuring of anchovy and sardine populations in the Bay of Biscay. The results revealed:
(i) the appearance of genetic differences linked to the age of individuals;
(ii) the appearance of allozymic differences (phenotypes) associated with a geographical distribution of individuals from the same breeding year;
(iii) the change in the genetic structure of the cohorts over time (possible effect of variations in recruitment);
(iv) a separation of individuals from coastal and offshore stations based on the IDH-2* locus (Laurent 2005).

In sardines, on the scale of the Bay of Biscay, the analysis of the genetic structure showed an absence of spatial and temporal structuring. However, the same analyzes carried out on samples from adjacent areas suggest well-differentiated populations between the Bay of Biscay, the Mediterranean, Morocco, the Azores Islands and Madeira, but the border between the Bay of Biscay and Gibraltar remains to be confirmed ( Lawrence 2005). Data and knowledge on Gulf anchovies in spring from PELGAS have been integrated into two syntheses on the life cycles of small pelagic fish on the European Atlantic seaboard (Petitgas et al. 2010); (Petitgas et al. 2011c).

Following results showing the impact of spawning dates and winter conditions in year n on spawning (period, duration, quantity) in year n+1 (Pecquerie, 2007; Pecquerie et al., 2009 ), as well as the impact of this spawning (period, duration) on larval survival and consequently on recruitment, it proved necessary to develop a model of the entire anchovy life cycle. This aims to couple the IBM 3D larval model (Huret et al., 2010), extended to the entire life cycle, to the DEB bioenergetic model (Pecquerie et al., 2009). The latter is under development and makes extensive use of PELGAS data on anchovy eggs, larvae and adults as well as data on zooplankton and predators.

The study methods and knowledge on the life cycle of the anchovy in the Bay of Biscay from PELGAS were finally used to formulate hypotheses explaining the expansion of this species in the North Sea (Petitgas et al. 2012) .

 4.4. Decline of the condition of anchovies and sardines in the Bay of Biscay

A sharp decline in the condition (average weight) of anchovies and sardines from the Bay of Biscay was detected for the first time during a systematic analysis of the series of indicators provided by the campaign (Doray et al. 2018c). This decline in condition, particularly marked in fish of age 1 and 2, with the disappearance of older individuals, echoes similar observations made in the Mediterranean (Saraux et al., 2019; Van Bevere and al., 2014). The data from the PELGAS campaign were used in subsequent studies aimed at determining the biological processes at the origin of this decline in condition (Véron et al. 2020a,b; Defipel project).

5. Megafauna

The data collected during PELGAS, combined with aerial survey data, made it possible to map the mammals and seabirds present in the Bay of Biscay in the spring (Certain 2007).

The distribution of seabirds is variable according to taxonomic groups. Northern gannets and gulls are widely distributed throughout the Bay of Biscay, while guillemots are associated with the coastal zone near river plumes. Gulls are observed mainly in the northern part of the Gulf, near the coast (Certain 2007).

Regarding marine mammals, the common dolphin and the bottlenose dolphin are the two most frequently observed species. These two species show a clear spatial segregation: the bottlenose dolphin is abundant at the level of the edges and the outer half of the continental shelf, while the common dolphin abounds on the side at the 100m isobath, then above the continental slope. and beyond. The central sector, known as the large mudflat, is notably underpopulated with small cetaceans (Certain et al. 2008).

A retrospective analysis of the time series of megafauna abundance observed during PELGAS showed an increase in the abundance of about a third of the species, a decrease of another third, and a stability of the remaining third between 2004 and 2016. The relative abundance of species distributed offshore, including all cetaceans studied, has increased slightly (Authier et al. 2018).

6. Functioning of the pelagic ecosystem of the Bay of Biscay

The work carried out within the PELGAS team has made it possible to routinely produce two types of standard ecosystem products from data from the PELGAS campaign:

•      maps of the parameters collected in the different compartments, averaged each year on a standard mesh;
•      series of state and spatial indicators, derived from the small pelagic fish biomass assessment process and standard maps.

The existence of these standard ecosystem products has made it possible to develop methods aimed at simultaneously analyzing information collected in different compartments of the ecosystem. The first objective was to highlight recurring spatial patterns in all compartments (or pelagic landscapes), in order to map the pelagic ecosystem of the Bay of Biscay, and to formulate hypotheses on the interactions between compartments. Pelagic landscapes that are recurrently present in the Bay of Biscay in spring have thus been highlighted, based on standard PELGAS maps (2009-2014), and their temporal variability has been estimated (Petitgas et al. 2018a). This study has opened up prospects for the characterization and monitoring of spatial patterns within ecosystems, the definition of indicators making it possible to assess the impact of human activities on the spatial structure of ecosystems and the analysis of the Bay of Biscay as a meta-ecosystem.

The second objective of the integrated analysis of PELGAS ecosystem data was to offer a concrete contribution to the issue of assessing the state of marine ecosystems, based on indicators from integrated ecosystem campaigns. Indicators of the state of the ecosystem have been defined from 143 candidate indicators from PELGAS data, and the main trends in their temporal dynamics have been characterized from 2000 to 2015 (Doray et al. 2018c). The study made it possible to select 26 indicators that presented the most continuous temporal trends in each of the main compartments of the ecosystem. The selected indicators confirmed the importance of river inputs, bottom temperature, chlorophyll and mesozooplankton concentration in bottom-up forcing of the Bay of Biscay pelagic ecosystem. According to the indicators selected and their trends, the populations of small pelagic fish have followed distinct trajectories over the 15 years analyzed in this study. Only the average weights of anchovies and sardines of age 1 and 2 showed similar downward trends. This synchronous decrease in mean weights could indicate the existence of density-dependent competition for food between young anchovy and sardine adults. This study showed the virtual absence of significant correlation between the indicators from PELGAS summarizing the evolution of the pelagic ecosystem and the indicators of fishing pressure and climate change in the Bay of Biscay. These results suggest that fishing pressure on small pelagic fish in the Gulf is moderate. They confirm that global climate change is currently having relatively limited effects on the pelagic ecosystem of the Bay of Biscay, compared to seasonal variability (Doray et al. 2018c).

PELGAS has also supplied data and concepts to several studies or models focusing on the overall functioning of the pelagic ecosystem of the Bay of Biscay. Most of the studies have been devoted to the interactions between trophic levels of the ecosystem.

Modeling exercises using PELGAS data have made it possible to integrate knowledge of carbon transfer from plankton to small pelagic fish (E. Marquis et al. 2007; Elise Marquis et al. 2011). These studies showed that the amount of carbon transferred from plankton to higher trophic levels was fairly constant, but the recipients varied widely depending on the structure of the plankton community. Small pelagic fish would thus benefit from a maximum of carbon transfer in the case of planktonic trophic chains dominated by small autotrophic cells, whereas chains dominated by large phytoplanktonic cells would benefit more from benthic communities, with losses of by sedimentation (E. Marquis et al. 2007; (Marquis et al. 2011). Work also suggests that the low trophic levels and the detrital compartment would control the energy flows in the benthic, demersal and pelagic ecosystems of the plateau of the Bay of Biscay (Lassalle et al. 2011).The productivity of mesozooplankton and its influence on the anchovy population during PELGAS have also been studied using biochemical markers (Bergeron and Koueta 2011),(Bergeron et al. 2013).

PELGAS provided the data on stomach contents and spatial distributions of adults and eggs needed to carry out a study on predation on anchovy eggs. This study concluded that the cannibalism of adult anchovies on their own eggs was low and allowed to characterize the dietary overlaps between anchovies, sardines and sprat (intra-guild competition). The degree of overlap between anchovy and sardine egg distributions was negatively correlated with anchovy recruitment, which could confirm the existence of intra-guild predation by sardines on anchovy eggs (Ollivier et al. 2012).

At higher trophic levels, biological samples of cetacean prey collected during PELGAS, combined with the examination of stomach contents of stranded cetaceans, were used in a study of the energy content of cetacean prey (Spitz 2010). This work then made it possible to estimate the removals of pelagic fish theoretically made by top predators. Crossing information on the abundance of small cetaceans from overflights, specific compositions from PELGAS, the energy needs of these species and the energy value of their prey also made it possible to estimate that small cetaceans on the continental shelf would take between 40 and 80,000 tonnes of fish per year (hake, sardines, pout, horse mackerel and anchovies). However, it remains to be explicitly defined when and where the trophic interactions between small pelagics and top predators take place.

An initial response was provided by a study on the spatial correlation between the biomass distributions of small pelagic fish and the abundance distributions of top predators observed during PELGAS from 2003 to 2008 (Certain et al. 2011). These authors have highlighted spatial correlations between the average distributions of certain species of small pelagics and the average distributions of certain predators. These spatial prey-predator associations were also consistent with the hydrological landscapes of the Gulf. The spatial correlation between prey and predators within these associations was however highly variable at the scale of the year. This strong temporal variability probably denotes the existence of complex trophic interactions between small pelagic fish and their predators, certainly influenced both by the dynamics of the respective populations and by environmental forcing.

Lambert et al. (2019) showed that the fine-scale spatial co-occurrence of megafauna and their prey (small pelagic fish) during PELGAS was influenced by their functional traits, and that prey exhibited avoidance behavior in the presence of cetaceans, but not birds.

Biological samples taken during PELGAS were used in a study of the spatio-temporal variability of stable isotopes from all trophic levels and a wide variety of habitats in the Bay of Biscay (Chouvelon 2011) This study noted a high variability of isotopic compositions at specific, spatial and temporal levels, which invites to collect isotopic samples in very limited areas and time periods, otherwise there is a risk of confusing the effects of spatio-temporal and inter-specific variability (Chouvelon et al. 2012).

Adult biomass estimates and anchovy egg distribution maps from PELGAS were used to calibrate and validate the complex ISIS-FISH fishery simulation model (Lehuta et al. 2013), and then to assess the effectiveness of anchovy fishery management scenarios (Lehuta et al. 2010). The potential impact of fisheries on cetaceans has also been studied using food web models based on data collected during PELGAS (Lassalle et al. 2012).

7. International collaboration

The PELGAS cruise is attached to the ¿Fisheries Information System¿ of the Biology and Environment Resources Department of Ifremer. The campaign is carried out within the framework of the European Data Collection Framework, in order to provide useful data for the management of Community fisheries. The results are used by the working groups of the International Council for the Exploration of the Sea (ICES) WGHANSA, which assesses stocks of sardines, anchovies, and horse mackerel, and WGWIDE, which assesses stocks of mackerel, blue whiting, etc.

The campaign is coordinated at international level within the framework of the CIEM WGACEGG working group, in which France, Spain, Portugal, the United Kingdom and Ireland participate. This working group's mission is to standardize biomass assessment methods by acoustics and eggs (Doray et al. 2021) and to pool the results, in order to propose adult and egg abundance maps. small homogeneous pelagic fish covering the continental shelf from Gibraltar to Ireland. The group also produces maps of other ecosystem indicators already collected as part of the various campaigns: hydrological parameters and abundance of top predators (Massé et al. 2018).

8. Perspectives

The ecosystemic approach of PELGAS, innovative in its beginnings, is now in line with the new European Marine Strategy Framework Directive (MSFD) which aims to globally estimate the "good health" of marine ecosystems.

The short-term objective of PELGAS is on the one hand to collect data for the MSFD descriptors and on the other hand to produce indicators of the state of the pelagic ecosystem of the Bay of Biscay. The campaign can indeed provide, in addition to stock assessments of small pelagics, raw data and additional sets of indicators on hydrology, nutrient salts, phytoplankton, zooplankton, the spatial distribution of small pelagic fish ( adults and eggs) and megafauna over the entire Bay of Biscay shelf and eco-region scale.

A functional approach could be applied to the study of the interactions between all the compartments of the ecosystem, in order to test the statistical correlations of ecological processes. This would require collecting new data, particularly on the movements of the organisms.

The originality of the PELGAS cruise is to routinely collect data in all compartments of the pelagic ecosystem of the Bay of Biscay (Doray et al 2018a). Compartment-by-compartment analysis of these data made it possible to produce a wealth of knowledge on the specific functioning of each of the compartments summarized here and the impact of fishing. However, the existence of this unique database of ecosystem data also made it possible to carry out a cross-compartment analysis to globally characterize the spatio-temporal dynamics of the pelagic ecosystem of the Bay of Biscay in spring. This innovative approach required the development of methods for the comparison and integrated analysis of cartographic data and indicators drawn from PELGAS data. The results were published in 2018 in a special issue of Progress in Oceanography.

At the same time, "PHOENIX" technological research campaigns were carried out by the PELGAS team in order to continue testing and developing new sensors (broadband acoustics, undulating towed body, etc.) and processing methods (planktonic imaging ... ) more automatic, in order to further increase the amount of ecosystem data routinely collected during PELGAS. The campaign will thus be able to continue to fulfill its dual role: sentinel of the Gascony pelagic ecosystem in a changing world and provider of data, knowledge and concepts to feed ecosystem models.