Distribución batimétrica y tasas de crecimiento de las poblaciones de Eunicella verrucosa (Cnidaria: Gorgoniidae) a lo largo de las costas de Marsella (Francia)

Gorgonians are important organisms in the Mediterranean Sea, where they form rocky benthic communities. Four main species (3 Holaxonia and 1 Scleraxonia) are predominant in infra- and circalittoral communities of the northwestern Mediterranean basin. Other species, such as Eunicella verrucosa (Pallas, 1766), are more rarely encountered. The expansion to unusually shallow bathymetric levels has been noted in the region of Marseilles (France) (between 20 and 40 m depth). A ten-year monitoring of colonies was used to assess the growth rate according to age (size): from 3.33 cm year–1 (height 40 cm).En las comunidades mediterráneas, las gorgonias son especies emblemáticas que aportan estructura a las comunidades bentónicas de fondos rocosos. En la cuenca noroccidental, cuatro especies son abundantes en las comunidades infra y circalitorales. Otras especies se encuentran más raramente. Es el caso de Eunicella verrucosa (Pallas, 1766). Esta especie se ha extendido a niveles batimétricos inusuales en la región de Marsella (Francia) (entre 20 y 40 m). El seguimiento durante 10 años de colonias ha permitido estimar que la tasa de crecimiento es diferente según la edad (tamaño), variando de 3.33 cm año–1 (altura colonias 40 cm)

Evaluación de los sitios de asentamiento de Diplodus spp. (Sparidae) a lo largo de la costa rocosa de Marsella (Francia, Mediterráneo Noroccidental).

This work aimed at performing a large scale assessment of Diplodus spp. (Sparidae) nurseries along the rocky shore of Marseilles (France, NW Mediterranean) by locating and quantifying nursery microhabitats and estimating the settlement pattern along this shore in 2004. Nursery grounds of Diplodus spp. represented only 9% of the 52 km-long rocky shore of Marseilles. Their location, shallow rocky habitats sheltered within coves, made them vulnerable to human-induced habitat transformations. D. vulgaris settled along this coast at the end of February 2004 and D. puntazzo settled a couple of months earlier. Maximum densities observed reached 215 and 67 ind./100 m for D. vulgaris and D. puntazzo respectively. The settlement rates were spatially variable. At a regional scale, lower settlement rates were observed within the south and centre zones, compared to those observed in the west, east, and the Marseilles Bay zones. Suitable nurseries along this shore seem insufficient for the replenishment of adult assemblages, which suggests that they depend on the migration of adults from other areas. Along the Marseilles rocky shore, coastal development projects leading to the destruction of habitats would represent a major threat to the Diplodus life cycle, which could be even greater than usual given the vulnerability and small size of the nurseries. These results show that it is necessary to protect these scarce local nursery habitats and manage other nearby nurseries to ensure the survival of fish at a critical life stage and the replenishment of adult assemblages.Este estudio tiene por objetivo realizar una evaluación a gran escala de las áreas adecuadas para el asentamiento de Diplodus spp. a lo largo de la costa rocosa de Marsella (Francia, Mediterráneo Noroccidental) a través del estudio de la ubicación y abundancia de estos microhábitats y del patrón de asentamiento durante el año 2004. Los microhábitats de asentamiento representaron tan sólo el 9% de los 52 km de las extensas costas rocosas de Marsella. Su ubicación en el interior de las calas, en substratos rocosos protegidos y a poca profundidad, los convierte en hábitats vulnerables a las transformaciones inducidas por el hombre. El asentamiento a lo largo de esta costa tuvo lugar a finales de febrero 2004 para D. vulgaris, y dos de meses antes para D. puntazzo. Las máximas densidades observadas por cada 100 metros de costa alcanzaron 215 y 67 individuos de D. vulgaris y D. puntazzo respectivamente. Las tasas de asentamiento fueron variables en el espacio. A escala regional, las tasas de asentamiento menores fueron observadas en las zonas sur y central. Los lugares de asentamiento adecuados a lo largo de esta costa parecieron insuficientes para abastecer las poblaciones adultas, lo que sugiere que éstas dependen de la migración de adultos desde otras áreas. La urbanización de la costa produciría destrucción de estos microhábitats, lo que pondría en peligro el ciclo vital de Diplodus, dada la vulnerabilidad y rareza de dichos microhábitats. Nuestros resultados mostraron la necesidad de proteger estos escasos hábitats de asentamiento y gestionar zonas de asentamiento a su alrededor para asegurar la conectividad entre hábitats, la supervivencia de determinadas fases críticas de los peces y el suministro de individuos a las poblaciones adultas

Symbiont diversity is not involved in depth acclimation in the Mediterranean sea whip Eunicella singularis

In symbiotic cnidarians, acclimation to depth and lower irradiance can involve physiological changes in the photosynthetic dinoflagellate endosymbiont, such as increased chlorophyll content, or qualitative modifications in the symbiont population in favour of better adapted strains. It has been argued that a lack of capacity to acquire new symbionts could limit the bathymetric distribution of the host species, or compromise its long-term survival in a changing environment. But is that always true? To address this question, we investigated the symbiont genetic diversity in Eunicella singularis, a Mediterranean sea whip species with a wide bathymetric distribution (10 to 50 m depth), which has recently suffered from mass mortalities after periods of abnormally high sea temperatures. We measured symbiont population densities and chlorophyll content in natural populations, and followed the response of the holobionts after reciprocal transplantations to deep and shallow depths. A total of 161 colonies were sampled at 2 depths (10 and 30 m) at 5 sites in the northwestern Mediterranean. All colonies harboured a single ribosomal Symbiodinium clade (A'), but a relatively high within-clade genetic diversity was found among and within colonies. This diversity was not structured by depth, even though the deeper colonies contained significantly lower population densities of symbionts and less chlorophyll. We did, however, reveal host-symbiont specificity among E. singularis and other Mediterranean cnidarian species. Transplantation experiments revealed a limit of plasticity for symbiont population density and chlorophyll content, which in turn questions the importance of the trophic role of Symbiodinium in E. singularis

The effect of protection level on a coastal fish community at Scandola, Corsica

Le peuplement ichtyologique de la zone infralittorale de la Réserve naturelle de Scandola (Corse) a été étudié en juillet 1988 par une méthode non destructive de relevés visuels en plongée, sur milieu rocheux et dans l'herbier à Posidonia oceanica. La comparaison des stations dans et hors de la réserve intégrale (toutes formes de pêche y sont inderdites) permet d'évaluer le rôle de la protection résultant de la mise en réserve. La densité et la biomasse moyennes sont comparables entre stations d'herbier : 3 ind./10m2 (0 à 25m), 56-66g PH/m2 (0 à 10m) et 35g PH/10 m2 (10 à 25 m). Par contre, la structure démographique et l'importance relative des espèces dominantes varient entre la réserve intégrale et non intégrale. Sur milieu rocheux, les différences sont plus tranchées : 0.6 contre 0.1 ind/10m2 et 202 contre 42g PH/10m2 entre la réserve intégrale et non intégrale. L'importance d'une réserve intégrale est donc plus évidente en milieu rocheux. Dans l'herbier, elle se traduit plus par une structure spécifique du peuplement de poissons mieux équilibrée que par une modification de sa densité ou de sa biomass

Occurence of barred knifejaw, Oplegnathus fasciatus (Actinopterygii: Perciformes: Oplegnathidae), in Malta (Central Mediterranean) with a discussion on possible modes of entry

The barred knifejaw, Oplegnathus fasciatus (Temminck et Schlegel, 1844), a species native to the North Western and Eastern Central Pacific, is recorded from the central Mediterranean for the first time. Two individuals were photographed within a month of each other in Grand Harbour and in Marsamxett Harbour, Malta. It seems likely that the fish were introduced by shipping and different scenarios how this may have happened are discussed.peer-reviewe

Fish assemblages along the coasts of Tunisia: a baseline study to assess the effectiveness of future Marine Protected Areas

The present study investigated coastal fish assemblages, using Underwater Visual Census (UVC) transects, in Tunisia (south Mediterranean basin). The rationale behind this work is to get i) a suggestive evidence about the status of fish assemblages, and ii) baseline data at 3 locations in Tunisia where 3 MPAs will be established, before the implementation of protection measures. At each location, we used a sampling design where fish censuses were performed in two types of zone: zones that will be inside MPAs, and zones that will remain outside. On the whole, 49 taxa belonging to 19 families were censused. Data reveal clear symptoms of overfishing, especially in terms of dominance of small- and medium-sized individuals of commercially relevant species. Our analyses, moreover, did not show any significant difference in whole fish assemblage structures (considering both density and biomass), patterns of average species richness, total fish density and biomass, density and biomass of different trophic categories of fishes, size distribution of commercially relevant species, between future-protected and unprotected zones. Overall, results suggest that 1) current fish assemblages at the three studied locations are likely to be seriously impacted by fishing activities, and 2) these data could be used as reliable baselines to assess the effectiveness of protection measures within the MPAs that will be established in the future. Our study is the first in Tunisia, and in North African coasts, that assessed distribution patterns of coastal fish assemblages by means of UVC, using a formal spatially replicated sampling design for resource management

Biología reproductiva de Diplodus sargus sargus en el golfo de Túnez (Mediterráneo)

The sexual activity of Diplodus sargus sargus in the Gulf of Tunis takes place from January to May. Spawning occurs in spring (March to May), as the water temperature rises from 15 to 18°C, just after the winter minimum. The spawning period increases as the latitude decreases. The overall male to female ratio was statistically different from unity. Size at sexual maturity (TL50) was 21 cm (4 years old). The length-weight relationship for all individuals was described by the following parameters: a = 0.015 and b = 3.051. D. s. sargus from the Gulf of Tunis is a rudimentary hermaphrodite with partial protandry.La actividad sexual de Diplodus sargus sargus del golfo de Túnez tiene lugar de enero a mayo. La puesta tiene lugar en primavera (marzo a mayo), cuando la temperatura del agua sube de 15 a 18°C, justo tras el mínimo invernal. A medida que la latitud decrece se observa un periodo reproductivo progresivamente más extenso. La relación machos/hembras fue significativamente distinta de uno. La talla de madurez sexual (TL50) fue 21 cm (4 años). La relación talla-peso para todos los individuos se describió por los siguientes parámetros: a = 0.015 y b = 3.051. D. s. sargus del golfo de Túnez es un a hermafrodita rudimentario con proterandría parcial.

Seagrass Posidonia oceanica (L.) Delile as a marine biomarker: A metabolomic and toxicological analysis

A human-made environmental disaster due to the shipwrecked of Costa Concordia cruise vessel on the Tuscan Island of Giglio (Italy) coast and the possible pollutants release has been feared, so requiring the activation of removal operations and the monitoring of the marine environment. In the present study, the seagrass Posidonia oceanica (L.) Delile was used as a bioindicator for the impact of the Costa Concordia accident on the marine and coastal habitat. Different P. oceanica samples were collected in the shipwrecked site under different light conditions. Using high-performance thin-layer chromatography, metabolic analysis of the samples was carried out in order to highlight possible changes in the secondary metabolism due to the permanent shading and the presence of pollutant traces. Moreover, sample mutagenicity, as a consequence of the possible absorption of environmental toxicants leaked by the wreck, was assessed by the Ames test. The results highlighted the permanence of the Concordia-induced alteration in the plant secondary metabolites. However, absorption of chemical pollutants and carcinogens was not reported; this point was confirmed by the lack of mutagenic effects found for the samples tested. Our results clearly evidence that the environmental impact of Costa Concordia wreck and removal operations on P. oceanica was mainly due to the lack of light in the marine habitat. Present methodological approach, which combines metabolomic and genetic ecotoxicological analysis, could represent a suitable strategy to evaluate the impact of human disasters on the ecosystem and to monitor the environmental changes

Biometric Fish Classification of Temperate Species Using Convolutional Neural Network with Squeeze-and-Excitation

submittedVersio

Effect of depth and canopy height on the nursery value of Cystoseira balearica forests for Mediterranean rocky reef fishes

We studied effects of depth and Cystoseira balearica forests canopy height on coastal juvenile fish assemblages of Minorca Island. Results showed a clear differentiation of juvenile fish assemblages due to depth: assemblage in the shallowest range (3-4m) was characterized by higher densities of Thalassoma pavo, deeper ones (6-8, 10-12 m) by higher densities of Coris julis. Smallest juveniles of both species were more abundant within forests displaying the highest canopy height; meanwhile largest juveniles were more abundant within low Cystoseira forests. Also, both species showed predominantly a cryptic behavior on forest of higher canopy height, and a temporal one when canopy was lower. This study supports the importance of preserving healthy Cystoseira forests in order to preserve their nursery value for these two Labrid species0,000