Monitoring fish species populations in very turbid environments is challenging. Acoustic cameras allow work in very poor visibility but are often deployed as a fixed observation point, limiting the scope of the survey. A BlueView P900-130 acoustic camera was deployed in rocky marine habitats off the coast of French Guiana in order to assess the total abundance, size structure and spatial distribution of a demersal fish population. The relevancy of using an acoustic camera to achieve these three objectives was evaluated by comparing acoustic data to those obtained from fishing surveys. The detection and identification of large demersal fish species were possible with the shape and size of the acoustic signal and acoustic shadow silhouette as well as swimming behavior. Mobile surveys combined with stationary surveys increased the probability of distinguishing individuals from inanimate objects. Estimated total length based on the acoustic signal underestimated the actual length of fish measured on deck, but the data showed the same trends in spatial and temporal variation. Acoustic cameras overcame the extreme lack of visibility by increasing knowledge of fish use of habitat, therefore providing much more efficiency in the effort, more accurate data on the abundance, size structure and spatial distribution than the fishing method. Thus, despite few limitations, acoustic camera surveys are far superior to fishing surveys in evaluating large demersal fish stock status.

The variability of the phytoplankton biomass derived from daily chlorophyll-a (Chl-a) satellite images was investigated over the period 1998–2017 in the surface waters of the English Channel and the northern Bay of Biscay. Merged satellite (SeaWiFS-MODIS/Aqua-MERIS-VIIRS) Chl-a was calculated using the OC5 Ifremer algorithm which is optimized for moderately-turbid waters. The seasonal cycle in satellite-derived Chl-a was compared with in situ measurements made at seven coastal stations located in the southern side of the English Channel and in the northern Bay of Biscay. The results firstly showed that the satellite Chl-a product, derived from a suite of space-borne marine reflectance data, is in agreement with the coastal observations. For compliance with the directives of the European Union on water quality, time-series of 6-year moving average of Chl-a were assessed over the region. A clear decline was observed in the mean and 90th percentile of Chl-a at stations located in the mixed waters of the English Channel. The time-series at the stations located in the Bay of Biscay showed yearly fluctuations which correlated well with river discharge, but no overall Chl-a trend was observed. In the English Channel, the shape of the seasonal cycle in Chl-a changed over time. Narrower peaks were observed in spring at the end of the studied period, indicating an earlier limitation by nutrients. Monthly averages of satellite Chl-a, over the periods 1998–2003 and 2012–2017, exhibited spatial and temporal patterns in the evolution of the phytoplankton biomass similar to these observed at the seven coastal stations. Both the in situ and satellite Chl-a times-series showed a decrease in Chl-a in the English Channel in May, June and July. This trend in phytoplankton biomass is correlated with lower river discharges at the end of the period and a constant reduction in the riverine input of phosphorus through improvements in the water quality of the surrounding river catchments.

Coccolithophore blooms occur regularly from April to June in the Bay of Biscay where they have been observed for many years from ocean-colour imagery thanks to the ability of their calcite plates to scatter light. They are easily depicted on interpolated images of non-algal Suspended Particulate Matter (SPM) derived from satellite reflectance data in May, at the time of the PELGAS (PELagique GAScogne) annual surveys. During the spring from 2012-2015, the PELGAS surveys provided in-situ data on the turbidity throughout the water column and on the hydrological environment prevailing during the blooms in the vicinity of the continental shelf break. The satellite-derived SPM in the area of coccolithophore blooms was closely related to measured turbidity in the euphotic zone. The deep maxima of coccolithophore-derived biomass were well observed in the turbidity signal throughout the water column. Despite the recurrence of SPM patterns due to coccolithophores in the well-mixed waters over the shelf break in spring, the variability of the satellite-derived SPM and the turbidity profiles was particularly high during the four years studied. The year 2013 showed persistent blooms from mid-April to the end of May over large areas inside and outside the shelf waters, whereas no bloom was observed in 2014, neither on SPM images nor through turbidity profiles. The presence or absence of coccolithophore blooms during the years 2012-2015 seem to be related to the degree of stratification of the water column, with more intense blooms occurring during mixed conditions. These results should improve classification of the PELGAS surveys from those occurring in a coccolith-rich environment, synonymous with mixed and cold waters, to those occurring in a coccolith-poor environment where surface waters are warmer and more stratified.

Suspended marine benthic microalgae in the water column reflect the close relationship between the benthic and pelagic components of coastal ecosystems. In this study, a 12‐year phytoplankton time‐series was used to investigate the contribution of benthic microalgae to the pelagic system at a site along the French‐Atlantic coast. Furthermore, all taxa identified were allocated into different growth forms in order to study their seasonal patterns. The highest contribution of benthic microalgae was observed during the winter period, reaching up to 60% of the carbon biomass in the water column. The haptobenthic growth form showed the highest contribution in terms of biomass, dominant in the fall‐winter period when the turbidity and the river flow were high. The epipelic growth form did not follow any seasonal pattern. The epiphytic diatom Licmophora was most commonly found during summer. As benthic microalgae were found in the water column throughout the year, the temporal variation detected in the structure of pelagic assemblages in a macrotidal ecosystem was partly derived from the differentiated contribution of several benthic growth forms.

Abstract. Evaluate the impact of anthropogenic CO2 uptake and acidification on the most abundant calcareous phytoplankton, coccolithophores, requires a better knowledge of the temporal and spatial evolution of their blooms. Here we determine, from satellite radiance, the seasonal and interannual variability of coccolithophore blooms for 18 years (1998 to 2015) across the North-East Atlantic region covering the Bay of Biscay and the Celtic Sea. The identification of coccolithophores is carried out using a modified version of the fuzzy method developed by Moore (2009) applied to a time series of SeaWiFS (1998–2003) and MODIS (2003–2015) spectral radiance. After identification of the coccolith pixels, the abundance of coccoliths is assessed from a data base of non-algal Suspended Particulate Matter (SPM), a product initially developed for estimating the content of mineral particles, mainly due to resuspension effects, in coastal waters. The results, in terms of identification and quantification, are consistent with in situ observations in the area and with those of algorithms addressing coccolithophore blooms at global scale (CALCITE and PHYSAT). Although a regular pattern in the phenology of the blooms is observed, starting south in April in Biscay and moving northwards until July near Ireland, there is a high seasonal and interannual variability in the extent of the blooms. Year 2014 shows very low concentrations of coccoliths from space (twice less than average) and anomalies point out the maximum level for 2001. The cause of the seasonal and interannual variability of the coccolithophores blooms in this Atlantic region remains an open question.

The purpose of this paper is to investigate the environmental nature of the French Guiana shrimp fishery dynamics through an empirical analysis. To do so, we specify a global harvest production function, in which the output depends on the number of days at sea and the stock level. In addition, we use some environmental variables representing the ‘El Niño’ and ‘la Niña’ phenomena, the sea surface temperature, and the flow of some Amazonian rivers as instruments. This method enables us to correct the well-known simultaneous bias between the harvest and the stock levels and to show that harvest is significantly dependent on the environmental factors analyzed, which may compromise the future of the French Guiana shrimp fishery in the context of climate change.

The age and growth of the Critically Endangered Atlantic goliath grouper Epinephelus itajara of equatorial French Guiana was determined by a non-lethal aging method using dorsal fin rays. Goliath grouper deposit 1 complete annulus per year, with the translucent zone of the annulus laid down at the beginning of the dry season (July). Two readers independently applied the method; there was full agreement between the two for 52% of the fish, and agreement of +/- 1 yr for 82%. Comparison of ages derived from paired samples of otoliths and fin rays were identical (n = 6). The mean age of goliath grouper was 4.2 yr (range = 1 to 17 yr; n = 229); 82% of the individuals were under the size/age of sexual maturity. Goliath grouper in French Guiana are larger at a given age and reach their asymptotic length (L-infinity = 192.3 cm) faster (k = 0.20 yr(-1)) than goliath grouper from the west coast of Florida, USA (L-infinity = 200.6 cm, k = 0.126). Total mortality, estimated from a catch curve of the age distribution, was about 0.65 both in the Grand Connetable Island marine protected area in French Guiana (where fishing is prohibited) and outside of the reserve, suggesting that the reserve does not protect goliath grouper from illegal fishing. However, the estimates of total mortality in both fished and protected sites likely includes emigration, because goliath grouper may use rocky sites in French Guiana as a nursery habitat and may not remain there once they mature.

The ecology, particularly the trophic ecology, of the Critically Endangered goliath grouper Epinephelus itajara (Lichtenstein 1822) in French Guiana (France) is relatively unknown. Such information would provide a better understanding of the role that goliath groupers play in the marine ecosystem of French Guiana. This study focused on the feeding ecology of the goliath grouper through stomach-content and stable-isotope analyses of captured specimens. The dietary composition of goliath groupers in French Guiana was similar to that of goliath groupers from other areas of the species' range. However, in French Guiana, goliath groupers exhibited an ontogenetic shift in diet that has not been demonstrated elsewhere. Crustaceans, primarily crabs, were dominant in the diet of smaller individuals (<120 cm), whereas demersal fishes, particularly catfish (Siluriformes), dominated the diet of larger individuals. Analysis of delta C-13 and delta N-15 in muscle samples indicated that: (1) larger fish fed more on higher trophic levels; (2) low seasonal and spatial variation existed in the diet; and (3) an apparent migration of early juveniles occurred from mangrove areas to rocky reefs. In French Guiana, adult and juvenile goliath groupers share marine rocky habitat, and the data suggest they may avoid food competition by a shift in diet with size.

Afin de produire des Indices de Composition pigmentaires (Ic), les indices de similarite de Bray-Curtis et de Kulczynski ont ete calcules sur les matrices pigmentaires brutes (HPLC) et confrontes aux indicateurs de pressions disponibles, essentiellement nutriments et biomasse chlorophyllienne. Un volet est dedie a la facade atlantique et un autre a la Manche orientale.

La realisation des campagnes halieutiques Polka et Guyaviv2 au large des cotes guyanaises a la fin des annees 80 a permis d’obtenir les relations biometriques qui ont ete utilisees depuis cette date pour tous les calculs des captures (spectres par classe de taille) et des evaluations annuelles du stock de vivaneaux (Lutjanus purpureus) (Etienne Prevost 1989; E. Prevost et Tous 1989; Lampert 2012a) Plus de vingt ans apres, nous pouvons nous poser la question de la pertinence de ces relations de nos jours. Des changements dans les parametres de croissance de L. purpureus ne sont pas a exclure suite aux changements climatiques et a la pression de peche exercee depuis quelques decennies. Ces changements pouvant alors se traduire par des variations dans les relations Taille-Poids (TP). Ce travail vise a mettre a jour les mesures de taille et du poids des individus echantillonnes lors des debarquements, afin d’etablir de nouvelles relations TP, ou confirmer les anciennes. Ce travail se borne aux relations TP de l’espece Lutjanus purpureus, qui represente a elle seule, plus de 90 % des debarquements de vivaneaux en Guyane. Cette espece est notamment utilisee pour les calculs du stock annuel du vivaneau du plateau guyanais.

Hydrological and photosynthetic parameters were investigated monthly from November 2009 to December 2010 using an opportunity ship, along a transect in the central part of the English Channel. A powerful statistical method, a Partial Triadic Analysis (PTA), was applied on the physicochemical data set and highlighted the functioning of four different ecosystems: (i) the French coast area (FRcoast) subjected to large freshwater inputs, (ii) the North of the Seine Bay (NSBay) influenced by nutrient inputs from the river Seine and offshore, (iii) the centre of the English Channel (CentreEC) characterized by nutrient offshore inputs and (iv) the English coast area (UKcoast) which exhibits low nutrient concentrations despite the proximity of the English coast. In the FRcoast and the NSBay the phytoplankton biomass peaked from mid-January to June. In contrast, in the UKcoast the phytoplankton biomass peak occurred from mid-November to March. In addition, we noticed that these coastal ecosystems showed two types of photosynthetic regulations. Photoacclimation mechanisms were observed in the FRcoast and the NSBay and a control of the photosynthetic parameters by nutrients in the UKcoast. This study highlights the importance of a “top down” control in winter/spring and underlines a complex situation in autumn with an uncoupling between rETRmax and the Chlorophyll a biomass. In order to understand this uncoupling it is necessary to estimate the loss due to zooplankton grazing and viral lysis as well as carbon excretion.

La peche represente la troisieme force economique en Guyane. Elle comprend trois secteurs : la peche industrielle a la crevette, la peche industrielle au Vivaneau et le peche cotiere, qui regroupe tous les petits navires dissemines sur les cotes guyanaises. La peche crevettiere a connu une diminution de debarquements depuis 1999, et cette tendance s’est fortement accentuee depuis 2007. Les professionnels, inquiets de cet etat de choses, se posent la question sur les causes de cette situation. Ce travail essaie de repondre a cette problematique avec le balayage de toutes les hypotheses, biotiques, abiotiques et liees a la peche elle-meme. L’analyse de la crise ne serait pas complete si la dimension economique n’etait pas prise en compte. Une analyse bio-economique est ainsi proposee en annexe, sous forme d’un article.