Sensitivity analysis of school parameters to compare schools from different surveys: a review of the standardisation task of the EC-FAIR programme CLUSTER

Echo traces seen on echo grams contain a lot of information about the aggregation of fish in schools. But the acosutic image obtained with a vertical biomass assessment echosounder contains distorsions mainly due to the beam angle, the equipment settings and the school depth. When the acoustic image of aggregation patterns changes over the years or varies between stocks, it is important to know up to what extent biological interpretation is meaningful!. The present paper reviews the work performed by a group of scientist within the EC FAIR programme CLUSTER. Simulations were performed to correct school parameters. Digital data were replayed to assess the importance of these corrections. Charts were derived to limit biological interpretation of changes on the school acoustic images

Vulnerability of the North Water ecosystem to climate change

High Arctic ecosystems and Indigenous livelihoods are tightly linked and exposed to climate change, yet assessing their sensitivity requires a long-term perspective. Here, we assess the vulnerability of the North Water polynya, a unique seaice ecosystem that sustains the world’s northernmost Inuit communities and several keystone Arctic species. We reconstruct mid-to-late Holocene changes in sea ice, marine primary production, and little auk colony dynamics through multi-proxy analysis of marine and lake sediment cores. Our results suggest a productive ecosystem by 4400–4200 cal yrs b2k coincident with the arrival of the first humans in Greenland. Climate forcing during the late Holocene, leading to periods of polynya instability and marine productivity decline, is strikingly coeval with the human abandonment of Greenland from c. 2200–1200 cal yrs b2k. Our long-term perspective highlights the future decline of the North Water ecosystem, due to climate warming and changing sea-ice conditions, as an important climate change risk

Acoustic detection of the spatial and temporal distribution of fish shoals in the Bay of Biscay

Echo sounder data were used to investigate the spatio-temporal variability of shoal behaviour in the Bay of Biscay. Data collected from annual surveys were processed using MOVIES-B software in order to mcasure this variability. The software was designed to measure morphological, energetic and space-time distribution descriptors from the acoustic signal received from fish shoals. Two surveys, DAAG 90 and DAAG 91, provided the appropriate characteristics for such an analysis. The survey's objective was to obtain relative abundance indices for the anchovy (Engraulis encrasicolus) biomass in the Bay of Biscay. The surveys were carried out in the same area (southern Bay of Biscay), at the same period (April) within one year interval (1990 and 1991), using the same equipment (vessel, acoustic system, fishing gear) in a multispecies environment. Frequency distributions for every descriptor were obtained and used to describe the acoustic detection of fish shoals. The analysis of frequency distributions of space-time descriptors (year, day-hour and bottom depth) allowed the construction of derived discrete variables, which defined new subsets of detections. The subsets were then described by the continuous variables. A principal components analysis was used to describe the multidimensional data structure and to describe behaviour patterns. The size and external outline unevenness are correlated groups of shoal descriptors, but are independent of the water column shoal position and the degree of internal shoal structure. An important feature is shoal size variability between years. Significant differences in shoal characteristics were found between bathymetric zones of the same region and the pattern was similar between years. This spatial wariability is related to the distribution of different species between bathymetric zones. Although it was not possible to explain size variability between years, this will be necessary to improve shoal characterization. More knowledge about oceanographic conditions, the productivity level and availability of food, predator pressure and accurate identification of shoal speeies is required, in order to study the spatial or temporal variability in size and behaviour of shoals

La gestion de l'eau et des milieux aquatiques en zone humide littorale endiguée : une dimension multi-usages à affirmer et de nouvelles démarches à mettre en oeuvre. Exemple du marais Breton / The management of water and aquatic environments in dyked coastal marshes ; in support of view and multi-user approaches ; the case of the "marais Breton" in France

Most reports refer to a large decrease of wetland zones, despite the increasing awareness of the necessity of their protection. An important factor explaining this contradiction would be the failure to appreciate the importance of water and aquatic biotopes in rural planning and management. Dyked marshes of the Atlantic coast are no exception to this rule. The necessity of water management on a watershed scale in a new multiuser context must lead to new rules for wetlands management. The Life-Norspa programme developed on the Marais Breton as part ot the "Schéma de mise en valeur de la baie de Bourgneuf" aims to define some indicators of the condition of these wetlands and to estimate the constraints resulting from their protection. Some pilot-schemes have been implemented to put these concepts of integrated water management into practice.La plupart des bilans font état d’une forte régression des surfaces des zones humides, malgré une prise de conscience croissante de la nécessité de leur sauvegarde. L'absence de prise en compte significative de l'eau et des milieux aquatiques dans les démarches développées sur ces territoires pourrait expliquer un tel décalage. Les marais endigués de la façade atlantique, en position intermédiaire entre continent et bande côtière, n'échappent pas à cette règle ; la nécessaire gestion de l'eau à l'échelle des bassins versants, dans un nouveau contexte de multi-usages, doit susciter une évolution notable des structures et des modes de gestion de ces territoires et de leurs milieux aquatiques. Le programme Life-Norspa engagé sur le marais Breton dans le cadre du Schéma de mise en valeur de la baie de Bourgneuf vise à déterminer des indicateurs d’état des zones humides et à préciser les contraintes liées à leur sauvegarde, en particulier sous l’aspect des peuplements piscicoles. Des aménagements témoins ont été réalisés pour mettre en application ces principes de gestion intégrée.Merle Valérie, Rigaud Christian, Massé Jacques. La gestion de l'eau et des milieux aquatiques en zone humide littorale endiguée : une dimension multi-usages à affirmer et de nouvelles démarches à mettre en oeuvre. Exemple du marais Breton / The management of water and aquatic environments in dyked coastal marshes ; in support of view and multi-user approaches ; the case of the "marais Breton" in France. In: Cahiers du Centre nantais de recherche pour l'aménagement régional, n°47-48, 1997. Littoral 95 - Actes du Colloque International Continuités et ruptures sur les littoraux européens. pp. 275-280

Micromesistius poutassou (blue whiting) abundance and biomass data in Bay of Biscay estimated from acoustic surveys (2000-2012)

Acoustic and pelagic trawl data were collected during various pelagic surveys carried out by IFREMER in May between 2000 and 2012 (except 2001), on the eastern continental shelf of the Bay of Biscay (Pelgas series). The acoustic data were collected with a Simrad EK60 echosounder operating at 38 kHz (beam angle at -3 dB: 7°, pulse length set to 1.024 ms). The echosounder transducer was mounted on the vessel keel, at 6 m below the sea surface. The sampling design were parallel transects spaced 12 nm apart which were orientated perpendicular to the coast line from 20 m to about 200 m bottom depth. The nominal sailing speed was 10 knots and 3 knots on average during fishing operations. The scrutinising (species identification) of acoustic data was done by first characterising acoustic schools by type and then linking these types with the species composition of specific trawl hauls. The data set contains nautical area backscattering values, biomass and abundance estimates for blue whiting for one nautical mile long transect lines. Further information on the survey design, scrutinising and biomass estimation can be found in Doray et al. 2012