Comportamiento de asociación al sustrato de las larvas bentónicas de Oblada melanura (Linnaeus, 1758) (Osteichthyes: Sparidae): una aproximación cuantitativa

The site-attachment behaviour of O. melanura settlers was examined in an estuarine area of western Greece. The approach that was followed included underwater assignments of shoal identities and continuous recording of specific behavioural traits. Variations between ontogenetic stages with respect to the pattern of residence at the sites were quantified via an index (the residence-persistence index (RPI)) devised for this purpose. Our findings suggest that this species initiates settlement in small shoals that occupy specific sites at the substratum where they reside for various days. This behavioural trait is stage-specific and gradually diminishes as the fish complete metamorphosis, while at the same time they change their social organisation. Such an ontogeny-dependent site-attachment behaviour has not been described before and is markedly different from that described for other members of the Sparidae family.En este trabajo se ha examinado el comportamiento de asociación al substrato de los individuos recién asentados de Oblada melanura en un área estuárica de Grecia occidental. El estudio se hizo en base a la identificación de los bancos y al seguimiento continuo de las características conductuales específicas a lo largo del tiempo. Las variaciones ontogenéticas respecto a la pauta de residencia en los diferentes lugares han sido cuantificadas mediante un índice (índice de residencia-persistencia (RPI) específicamente desarrollado para este fin. Nuestros resultados sugieren que esta especie inicia el asentamiento en pequeños bancos que ocupan lugares específicos del substrato en donde residen varios días. Esta característica conductual es específica del estadio de desarrollo y disminuye gradualmente a medida que los peces acaban su metamorfosis, mientras que, al mismo tiempo, cambian su organización social. Esta conducta de asociación con el lugar de asentamiento, dependiente de la ontogenia, no se había descrito anteriormente y es marcadamente diferente a la que ha sido documentada para otros miembros de la familia Sparidae

Improved predictive modelling of coralligenous formations in the Greek Seas incorporating large-scale, presence–absence, hydroacoustic data and oceanographic variables

Our understanding of the distribution of coralligenous formations, throughout but mostly on the Eastern Mediterranean seafloor, is still poor and mostly relies on presence-only opportunistic trawling and fishermen reports. Previous efforts to gather this information created relevant geodatabases that led to a first draft predictive spatial distribution of coralligenous formations in the Mediterranean Sea using habitat suitability modelling techniques. In the last few decades, the use of hydroacoustics to map the seafloor for various geotechnical and habitat mapping projects accumulated high amounts of detailed spatial information about these formations, which remains majorly unexploited. Repurposing these datasets towards mapping key habitats is a valuable stepping stone to implementing the EU Habitat Directive. In Greece, a unique volume of seafloor mapping data has been gathered by the Laboratory of Marine Geology and Physical Oceanography, Geology Department, University of Patras. It accounts for more than 33 marine geophysical expeditions during the last three decades, having collected hydroacoustic data for a total seafloor area of 3,197.68 km2. In the present work, this information has been curated, re-evaluated, and archived to create the most complete, until now, atlas of coralligenous formations in the Greek Seas and the only integrating presence–absence data. This atlas has been used to train and validate a predictive distribution model, incorporating environmental variables derived from open data repositories, whose importance has been assessed and discussed. The final output is an improved probability map of coralligenous formation occurrence in the Greek Seas, which shall be the basis for effective spatial planning, gap detection, and design of future mapping and monitoring activities on this priority habitat

Recrutement de la sole (Solea solea, L.) du golfe de Gascogne: influence de l'hydrologie et de l'hydrodynamisme

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79633 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

The stability of the spatial distribution of the pelagic stages of sole as explained by the trajectories of ARGOS satellite

The studies of the pelagic stages of Sole (Solea vulgaris , Quensel) in the northern part of the Bay of Biscay are strongly influenced by the recent concepts concerning the importance of the physical processes in the evolution of marine populations. The investigations of the linkage between water masses circulation and year-class strength started in 1986 with the deployment of 3 ARGOS satellite tracked drifters at different depths in parallel with the ichthyoplanktonic surveys. The trajectory of the 7 m drifter (tracking the water masses above the pycnocline) is related to the wind. This drifter leaves the sector of the study after 10 days. After 40 days of variable environmental conditions, the 34 m drifter (situated below the density gradient) was only at 10 miles from the releasing point.Les etudes sur les stades pelagiques de la Sole (Solea vulgaris, Quensel dans la partie nord du Golfe de Gascogne montrent de faibles differences dans la repartition spatiale durant le developpement embryonnaire et larvaire. La circulation des masses d'eau dans le secteur de la frayere a ete etudiee a l'aide de balises "Argos", su1v1es par, satellite. Les resultats obtenus en 1986 ont ete valides par les operations realisees en 1987. Les differences de trajectoire observees entre les drogues de 7 et de 34 m sont expliquees par la stratification de la colonne d'eau. Aprcs 40 jours de conditions meteorologiques variables, la balise ancree a 34 m etait a 10 milles du point de depart. Ces resultats suggerent que la stabilite spatiale des stades pelagiques peut etre expliquee par un comportement passif des oeufs et des jeunes larves et l'apparition·de preferences concernant la distribution verticale avec l'age

Tracing Patterns and Biodiversity Aspects of the Overlooked Skates and Rays (Subclass Elasmobranchii, Superorder Batoidea) in Greece

Species belonging to the superorder Batoidea have been poorly assessed due to the lack of information on their life history aspects and their limited economic value. This work presents an overview of skates and rays inhabiting the marine Greek waters and reports biodiversity issues requiring resolution for conservation purposes. Overall, 30 species from nine families and 16 genera have been documented within the past 22 years, based on the available literature and technical reports from research surveys of the Hellenic Centre for Marine Research (HCMR). However, 28 species are currently confirmed, since the presence of two rajids has not been sufficiently demonstrated and hence is considered as doubtful. Recent changes in nomenclature allowed us to replace old with new names in four species on the Greek list; patterns in the frequency of occurrence were observed and species were assigned into five categories; and diversity and misidentification issues were reported by family. Although Greek waters are oligotrophic and not considered a biodiversity hot spot for elasmobranchs, a high number of batoid species is documented in the area; therefore, the need to reinforce knowledge on biological aspects of skates and rays, define their status and identify their main threats is essential

Response of juvenile sole (Solea solea (L.)) to environmental changes investigated by otolith microstructure analysis.

Otolith microstructure analysis of sole juveniles, Solea solea (0-2 groups) sampled in the Bay of Vilaine, Bay of Biscay, was carried out using scanning electron microscopy. Daily increment analysis showed two cases growth retardation, recorded as narrow increment deposition during the first weeks after transition to the bottom-dwelling mode of life. It is assumed that the observed growth retardation of 0-group sole in the summer of 1982 might have been caused by the oxygen deficiency recorded in the Bay of Vilaine at that time. The same observation in otolith microstructure during late spring 1986 might be associated with a strong cold freshwater discharge recorded in the sampling area that affected both water salinity and temperature

Variaciones geográficas de la producción piscícola de la formación de marismas de Mesologi-Etolikó (Grecia occidental)

The Messolonghi-Etoliko lagoon is one of the largest lagoon system in the northern Mediterranean coast. This area contains six clearly distinct lagoons with different topographic and hydrological features. The fishery landings of the lagoons are based on the ontogenic and seasonal migrations of the species. The total annual fishery landings of the barrier fish traps are estimated as 195 mt and are mainly composed of 16 species belonging to 8 families. Eel (Anguilla anguilla), the four species of Mugilidae (Liza saliens, L. aurata, L. ramada and Mugil cephalus), the two species of Sparidae (Sparus aurata and Diplodus annularis) and one species of Mullidae (Mullus barbatus) represent more than 92% of the total annual landings. The composition of the fishery landings varies between lagoons. The cluster analysis showed three groups of lagoons. The first group comprised lagoons in which the landings were dominated by eel, the second group was dominated by Mugilidae species and S. aurata, and the third by L. ramada and M. cephalus. The diversity index of the fishery landings is fairly constant in time, except for the Etoliko lagoon, where repeated anoxic crises decreased the diversity index value to almost zero in 1992. All the landing series showed a dominant annual cycle. Two seasonal patterns of the fishery landings were observed and linked to the fish spawning behaviour and/or their reaction to environmental forcings. The first one concerns species caught from summer to early autumn and the second pattern concerns species trapped during their autumn to winter offshore migration.La formación de lagunas de Mesologi-Etolikó es una de las reservas naturales marinas más grandes de la franja septentrional del Mediterráneo. Este conjunto está compuesto por seis distintas marismas, con diferentes características topográficas e hidrográficas cada una de ellas. La producción piscícola de las marismas se basa en los movimientos estacionales de las especies hacia el mar. Del estudio del trampeo se concluye que los movimientos migratorios equivalen a 195 toneladas y se componen principalmente de 16 especies las cuales pertenecen a 8 familias: anguila (Anguilla anguilla), cuatro especies de Mugilidae (Liza saliens, L. aurata, L. ramada, y Mugil cephalus), dos especies de Sparidae (Sparus aurata y Diplodus annularis) y una especie de Mullidae (Mullus barbatus). Estas especies representan más del 92% de los desplazaminentos anuales. Estos varían entre las distintas marismas. El análisis cluster distingue tres tipos de marismas. El primer grupo incluye las marismas cuyos movimientos son principalmente de anguila; el segundo grupo de Mugilidae y de S. aurata, y el tercero con movimientos sobre todo de L. ramada y M. cephalus. Los desplazamientos de estas especies presentan un ciclo anual importante. Así mismo, se han observado dos clases de movimientos estacionales (en verano y a principios de invierno) que se asocian a los movimientos migratorios de estas especies hacia el mar para su reproducción y/o provocadas por consideraciones adversas

Déterminisme du recrutement de la sole. Phase pélagique - Résultats des campagnes 1985

In order to analyse the recruitment process of a commercial fish, the common sole has been selected for making researches into the mecanisms which have an effect upon the distribution of the young fish stages and upon the plenty of the recruitment. In 1985, during three surveys for eggs and larvae off the estuary of the river Loire in march and april, severa! points have been studied : - physical and chemical data of the sea - distribution of eggs and larvae - vertical distribution of larvae in a little scale - some results on nutrition of larvae.Afin d'analyser le processus du recrutement d'une espèce d'intérêt économique, la sole a été choisie pour rechercher les mécanismes déterminant la répartition des jeunes stades et influençant l'abondance de la phase recrutée.  En 1985, au cours de trois campagnes de récoltes d'oeufs et larves au large de l'estuaire de la Loire en mars et avril, plusieurs points ont été étudiés: - caractéristiques physiques et chimiques du milieu - distribution des oeufs et des larves - distribution verticale des larves à petite échelle - quelques résultats sur la nutrition des larves