Spatial distribution of pelagic fish off Adélie and George V Land, East Antarctica in the austral summer 2008

AbstractPelagic fish assemblages and community structure were examined along longitudinal and meridian transects off Adélie and George V Land, East Antarctica, in the austral summer 2008. Fish were sampled with an RMT 8 net principally from six discrete depth layers (0–50–100–200–500–1000–2000 m) in the oceanic zone and from three depth layers (0–50–100–200 m) over the continental shelf zone. A total of 20,281 individuals from 27 species were collected. Pleuragramma antarcticum was the most dominant species by number (18,710 inds), followed by Chionodraco hamatus (768), Trematomus newnesi (375), Cyclothone microdon (101), Electrona antarctica (92), Bathylagus antarcticus (51) and Notolepis coatsi (54). Cluster analysis revealed that the fish community was clearly divided at the Antarctic Slope Front into separate oceanic and shelf assemblages, being dominated by mesopelagic fish and notothenioids, respectively. The Southern Boundary of Antarctic Circumpolar Current likely restricted a more northern distribution of notothenioids in the upper 200 m. Mesopelagic fish dominated the large biomass below 500 m and notothenioids dominated that in the upper 100 m. It is considered that mesopelagic fish in the oceanic zone would unlikely be eaten by seabirds because no distinctive diel vertical migration to the surface layer was observed. In the neritic zone, notothenioids (C. hamatus, T. newnesi and P. antarcticum) possibly play an important role as prey items for flying seabirds, penguins and other notothenioids fish especially in the shallow depth stratum (0–100 m)

Antarctic marine biodiversity challenged by global change: the CAML/SCAR-MarBIN benchmark

There is now undisputed evidence that climate change and modifications of the Earth system occurs, at faster rates in the polar regions. Among the many consequences we will be facing, the loss of biodiversity is probably of highest concern. CAML and SCAR-MarBIN are striving to provide the baseline information needed to assess the potential impact of climate change on Antarctic marine biodiversity. Through strong science plans, efficient data management and an unprecedented collaborative research effort within the IPY framework, CAML and SCAR-MarBIN intend to provide to scientists, environmental managers and decision-makers a sound benchmark against which future changes can reliably be assessed. This paper gives a brief description of the project’s synergies

Pautas de distribución espacial y modelización mediante SIG del habitat de Larvas de Solea solea, Pleuronectes flesus y limanda en la parte oriental del Canal de la Mancha durante la primavera

The spring distribution of larval fish stages of flatfishes in the Dover Strait (eastern English Channel) was studied in 1995 and 1999. Fish larvae were identified and sorted according to developmental stages in order to study their ontogenic distribution. The French coastal waters are characterised by an unstable tide-dependent front, which influences larval dispersion. In spring, the French coastal waters have a high phytoplanktonic production. They have higher temperatures, lower salinities and differences in current intensity compared with the central English Channel waters. Generalised Additive Models (GAM) combined with Geographic Information Systems (GIS) were used to model the potential habitats of life stages considering data from three major surveys in this area. The models were developed by coupling presence-absence models with non-null abundance models. The potential habitat of larval stages was then mapped using a geostatistical method (kriging). This revealed different species strategies in which young stages were abundant in central waters and older ones were distributed mainly along the French and Belgian coasts. It is concluded that the central English waters are important for young stages after hatching and that coastal waters are essential nurseries for future juveniles. The models of three flatfish species having similar life cycle strategies are presented here: Limanda limanda, Platichthys flesus and Solea solea.Durante 1995 y 1999 se estudió la distribución primaveral de los estadios larvarios de peces planos en el Estrecho de Dover (parte oriental del Canal de la Mancha).Las larvas de peces fueron identificadas y separadas en función de su estadio de desarrollo con objeto de estudiar su distribución ontogénica. Las aguas costeras francesas se caracterizan por un frente de marea inestable, que influencia la dispersión larvaria. Durante la primavera, dichas aguas presentan una elevada producción fitoplanctónica. Asimismo, presentan altas temperaturas, bajas salinidades y diferencias en la intensidad de la corriente, comparado con las aguas centrales del Canal de la Mancha. A partir de datos obtenidos en tres amplias campañas en este área, se utilizaron Modelos Aditivos Generalizados (GAM) con Sistemas de Información Geográfica (SIG) para modelizar los hábitats potenciales de los estadios larvarios. Los modelos se desarrollaron uniendo modelos de “presencia-ausencia” con modelos de “abundancia no nula”. A continuación, usando métodos geoestadísticos (kriging) se representó el mapa del hábitat potencial de los estadios larvarios. Esto reveló diferencias en las estrategias de aquellas especies cuyos primeros estadios son abundantes en las aguas centrales y cuyos estadios más avanzados están distribuidos principalmente a lo largo de la costa francesa y belga. Se mostró la importancia de las aguas centrales del Canal de la Mancha para las larvas lecitotróficas, y como las aguas costeras son áreas de cría esenciales para los futuros juveniles. Aquí se presentan los modelos para tres especies de peces planos que tienen estrategias de vida similares: Limanda limanda, Platichthys flesus and Solea solea

Biological responses to change in Antarctic sea ice habitats

Sea ice is a key habitat in the high latitude Southern Ocean and is predicted to change in its extent, thickness and duration in coming decades. The sea-ice cover is instrumental in mediating ocean–atmosphere exchanges and provides an important substrate for organisms from microbes and algae to predators. Antarctic krill, Euphausia superba, is reliant on sea ice during key phases of its life cycle, particularly during the larval stages, for food and refuge from their predators, while other small grazers, including copepods and amphipods, either live in the brine channel system or find food and shelter at the ice-water interface and in gaps between rafted ice blocks. Fish, such as the Antarctic silverfish Pleuragramma antarcticum, use platelet ice (loosely-formed frazil crystals) as an essential hatching and nursery ground. In this paper, we apply the framework of the Marine Ecosystem Assessment for the Southern Ocean (MEASO) to review current knowledge about relationships between sea ice and associated primary production and secondary consumers, their status and the drivers of sea-ice change in this ocean. We then use qualitative network modelling to explore possible responses of lower trophic level sea-ice biota to different perturbations, including warming air and ocean temperatures, increased storminess and reduced annual sea-ice duration. This modelling shows that pelagic algae, copepods, krill and fish are likely to decrease in response to warming temperatures and reduced sea-ice duration, while salp populations will likely increase under conditions of reduced sea-ice duration and increased number of days of >0°C. Differences in responses to these pressures between the five MEASO sectors were also explored. Greater impacts of environmental pressures on ice-related biota occurring presently were found for the West and East Pacific sectors (notably the Ross Sea and western Antarctic Peninsula), with likely flow-on effects to the wider ecosystem. All sectors are expected to be impacted over coming decades. Finally, we highlight priorities for future sea ice biological research to address knowledge gaps in this field

Biological responses to change in Antarctic sea ice habitats

Sea ice is a key habitat in the high latitude Southern Ocean and is predicted to change in its extent, thickness and duration in coming decades. The sea-ice cover is instrumental in mediating ocean–atmosphere exchanges and provides an important substrate for organisms from microbes and algae to predators. Antarctic krill, Euphausia superba, is reliant on sea ice during key phases of its life cycle, particularly during the larval stages, for food and refuge from their predators, while other small grazers, including copepods and amphipods, either live in the brine channel system or find food and shelter at the ice-water interface and in gaps between rafted ice blocks. Fish, such as the Antarctic silverfish Pleuragramma antarcticum, use platelet ice (loosely-formed frazil crystals) as an essential hatching and nursery ground. In this paper, we apply the framework of the Marine Ecosystem Assessment for the Southern Ocean (MEASO) to review current knowledge about relationships between sea ice and associated primary production and secondary consumers, their status and the drivers of sea-ice change in this ocean. We then use qualitative network modelling to explore possible responses of lower trophic level sea-ice biota to different perturbations, including warming air and ocean temperatures, increased storminess and reduced annual sea-ice duration. This modelling shows that pelagic algae, copepods, krill and fish are likely to decrease in response to warming temperatures and reduced sea-ice duration, while salp populations will likely increase under conditions of reduced sea-ice duration and increased number of days of >0°C. Differences in responses to these pressures between the five MEASO sectors were also explored. Greater impacts of environmental pressures on ice-related biota occurring presently were found for the West and East Pacific sectors (notably the Ross Sea and western Antarctic Peninsula), with likely flow-on effects to the wider ecosystem. All sectors are expected to be impacted over coming decades. Finally, we highlight priorities for future sea ice biological research to address knowledge gaps in this field

Influence de l'hydrodynamisme, en Manche orientale, sur la qualité trophique du milieu, la croissance et la survie des larves d'un poisson plat, le flet (pleuronectes flesus L.)

La Manche est, en période printanière, représente un écosystème particulier pour le développement larvaire de nombreuses espèces et notamment pour les premiers stades de vie du flet, Pleuronectes flesus, par les processus hydrologiques et la présence d'un front hydrologique. A partir de campagnes à la mer et de données issues de campagnes précédentes, une base de données a été créée afin de regrouper et d'analyser l'ensemble des paramètres environnementaux et biotiques en relation avec la distribution larvaire. L'influence de l'hydrodynamisme a été étudiée à partir d'indices de condition physiologique et d'une approche des phénomènes d'osmorégulation des larves. L'analyse du tractus digestif a permis de définir la composition du régime alimentaire. En complément, pour définir la qualité nutritionnelle, l'observation de l'état des organes a été réalisée définissant une échelle graduelle de l'état physiologique...CALAIS-BU Sciences (621932101) / SudocSudocFranceF

Control of the spatial distribution of the spawning habitat of fish populations a multi-model approach (applied to North Sea plaice and whiting and bay of Biscay anchoy)

La reproduction est une phase importante du cycle de vie des poissons car elle assure le renouvellement du nombre d individus dans la population. La détermination des facteurs qui influencent sa dynamique spatiale est donc un point capital car elle va affecter le succès de la reproduction. Une approche multi-modèles a été développée afin d identifier les facteurs contrôlant la distribution spatiale des adultes reproducteurs pour la plie et le merlan de Mer du Nord et pour l anchois du golfe de Gascogne. Les modèles additifs généralisés ont été utilisés pour relier la présence-absence des individus et leurs abondances aux différentes hypothèses de contrôle externes (position géographique et environnement) et internes à la population (dépendance spatiale, taille, structure en âge et mémoire). Les modèles construits ont été classés en fonction de leur aptitude à refléter les distributions observées. Les hypothèses de contrôle importantes ont alors été identifiées à partir des meilleurs modèles. L habitat de reproduction montre une structuration très importante dans l espace. L approche multi-modèles révèle (1) l influence de l environnement sur l occupation des zones de reproduction et (2) le degré d abondance avec lequel ces zones sont occupées est déterminé par des facteurs internes à la population. La persistance dans le temps de la structuration spatiale de la reproduction est facilitée par un attachement des individus à leur site de reproduction. Celui ci est plus fort pour des bentho-démersaux comme la plie et le merlan que pour un pélagique comme l anchois.PARIS-BIUSJ-Physique recherche (751052113) / SudocPARIS-Museum-Bib. d'ichtyologie (751052306) / SudocSudocFranceF