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Four seasonal surveys were carried out in the Gulf of Tunis between summer 2002 and spring 2003 to study the abundance and distribution of Sardina pilchardus eggs and larvae in relation to environmental parameters. In the Gulf of Tunis, Sardina pilchardus begins spawning in autumn (23 eggs/10 m²) and attains its peak in winter (257 eggs/10 m²) when the mean SST is lowest (13.4°C). Sardine reproduction seems to be triggered by the decrease in the SST. In winter, the main spawning areas were located to the south of Zembra Island and the north of Cape Bon. Larvae were more abundant in winter (38 larvae/10 m²), while lower densities were collected in autumn and spring (1 larva/10 m²). The highest abundance of larvae (288 larvae/10 m²) was recorded southwest of Zembra Island. Eggs and larvae were mainly concentrated in the relatively warmer and saltier waters with high zooplankton abundance and, inversely, with a low concentration of nitrate and chlorophyll a and a low diatom abundance. Se llevaron a cabo cuatro campañas en el golfo de Túnez, entre verano del 2002 y primavera del 2003, con el objetivo de estudiar la abundancia y distribución de los huevos y larvas de Sardina pilchardus en relación con parámetros ambientales. En el golfo de Túnez Sardina pilchardus inicia la freza en otoño (23 huevos/10 m²), alcanzando el pico de puesta en invierno (257 huevos/10 m²), cuando la temperatura superficial media (SST) es mínima (13.4°C). La reproducción de la sardina se dispara al parecer por el descenso de la SST. En invierno, las principales áreas de puesta se localizaron al sur de la isla de Zembra y en el norte del Cabo Bon. Las larvas fueron más abundantes en invierno (38 larvas/10 m²); mientras que se recogieron menores densidades en otoño y primavera (1 larva/10 m²). La mayor abundancia larvaria (288 larvas/10 m²) fue observada en el suroeste de la isla de Zembra. Los huevos y larvas se concentraron principalmente en las aguas relativamente más cálidas y salinas, con altas abundancias de zooplancton, e inversamente bajas concentraciones de nitrato, clorofila a y abundancia de diatomeas.

WOS:000363709700003; International audience; In order to define the structure of trophic network of Ichkeul Lake in Tunisia, diet of main teleost fish species was determined during two seasons, wet and dry. A total of 491 stomachs from 16 teleost species was analyzed. The analysis revealed spatial variability (East under marine influence and West with more continental effect) and temporal one (wet and dry seasons). Based on stomach contents, nine trophic groups were revealed, including eight monospecific groups. The main prey are mudflat snails (Hydrobia ventrosa, H. acuta), bivalves (Abra alba, Cerastoderma glaucum), amphipods and isopods, as well as seagrass (Potamogeton pectinatus, Ruppia cirrhosa) and water brackish algae (Ulva spp. and Chaetomorpha spp., Cladophora sp., Polysiphonia sp.).

In this paper, we describe an exploited continental shelf ecosystem (Gulf of Gabes) in the southern Mediterranean Sea using an Ecopath mass-balance model. This allowed us to determine the structure and functioning of this ecosystem and assess the impacts of fishing upon it. The model represents the average state of the ecosystem between 2000 and 2005. It includes 41 functional groups, which encompass the entire trophic spectrum from phytoplankton to higher trophic levels (e.g., fishes, birds, and mammals), and also considers the fishing activities in the area (five fleets). Model results highlight an important bentho-pelagic coupling in the system due to the links between plankton and benthic invertebrates through detritus. A comparison of this model with those developed for other continental shelf regions in the Mediterranean (i.e., the southern Catalan, the northern-central Adriatic, and the northern Aegean Seas) emphasizes similar patterns in their trophic functioning. Low and medium trophic levels (i.e., zooplanlcton, benthic molluscs, and polychaetes) and sharks were identified as playing key ecosystem roles and were classified as keystone groups. An analysis of ecosystem attributes indicated that the Gulf of Gabes is the least mature (i.e., in the earliest stages of ecosystem development) of the four ecosystems that were compared and it is suggested that this is due, at least in part, to the impacts of fishing. Bottom trawling was identified as having the widest-ranging impacts across the different functional groups and the largest impacts on some commercially-targeted demersal fish species. Several exploitation indices highlighted that the Gulf of Gabes ecosystem is highly exploited, a finding which is supported by stock assessment outcomes. This suggests that it is unlikely that the gulf can be fished at sustainable levels, a situation which is similar to other marine ecosystems in the Mediterranean Sea. Crown Copyright (c) 2013 Published by Elsevier B.V. All rights reserved.

La patelle, Patella caerulea Linnaeus, 1758, est un mollusque gastéropode très fréquent sur toutes les côtes rocheuses tunisiennes. Elle expose des traits écologiques et comportementaux complexes qui varient d’un milieu à un autre. Dans cette étude, nous nous proposerons d’analyser la diversité morphométrique de P. caerulea peuplant trois sites rocheux des côtes nord de la Tunisie (Canal de Bizerte, La Goulette et Sidi Rais). Le test t de Student, le test "t" : de pente (tpe) et de position (tpo) ont été utilisés pour la comparaison des pentes et des positions des droites de régressions entre les 3 populations étudiées. A l’échelle globale, les résultats des trois relations allométriques (longueur-hauteur, longueur-largeur et largeur-hauteur), mises en évidence dans notre étude, ont montré que l’accroissement de la longueur de la coquille de P. caerulea est moins important que ceux de sa hauteur et de sa largeur, et que l’accroissement de la largeur est plus lent que celui de sa hauteur dans les trois régions étudiées. Il s’agit bien d’une réponse adaptative aux conditions physiques et écologiques du milieu. L’étude de l’évolution mensuelle des relations (longueur-hauteur et longueur-largeur) au niveau des trois stations a bien montré que les patelles ont tendance à croître en hauteur et en largeur plus rapidement qu’en longueur. Cette étude a montré que globalement, il existe une différence significative entre les caractéristiques morphométriques des trois populations étudiées. The limpet species, Patella caerulea (mollusks, gastropods) is very common in almost Tunisian rocky coasts. It shows complex ecological and behavioral characteristics which vary according to the environment where it lives. In this investigation we are interested in analyzing the morphometric diversity of the limpet from three rocky sites in the northern coasts of Tunisia (Bizerta Channel, La Goulette and Sidi Rais). Statistical tests: “student, tests t of slope and of position” have been used in order to compare the slopes and the positions of the regression straight line between the 3 studied population. Results showed that, according to the global scale, the three allometric relations highlighted in this work revealed that the increase of the length shell is less important than those of the height and the width. In another hand, the increase of the width is slower that the height one of all the specimens studied from the 3 sites. These results reflect the adaptative response of the limpet following the physical and the ecological environment where it lives. The monthly variation of the relations: length/height and length/width in the limpets from the 3 studied sites showed that this species has a tendency to growth in height and width faster than the length. This study revealed significant differences between the morphometric characteristics of the three limpet population. Published Limpet Patella caerulea morphometric characteristics

Le branchiopode Artemia représente le principal organisme vivant colonisant les biotopes hypersalés. L’étude taxonomique de l’Artemia au niveau de la région ouest méditerranéenne, incluant l’Italie, la France, l’Espagne, le Portugal et le Maroc, a révélé la présence de l’espèce Artemia franciscana (qui a pour origine le continent Américain) comme étant une espèce invasive. Dans ce travail, une nouvelle population d’Artemia a été rapportée pour la première fois au niveau de Sabkhet Halk El Manzel. Une première identification taxonomique de cette population a été réalisée moyennant une étude morphologique et comparative de la forme de l’ovisac des femelles avec cinq autres populations tunisiennes appartenant à l’espèce Artemia salina et avec l’espèce américaine Artemia franciscana du Great Salt Lake. Par ailleurs, une Analyse en Composante Principal et une Analyse Discriminatoire des différents paramètres morphologiques des spécimens adultes collectés in situ à partir de cinq populations tunisiennes d’Artemia salina prélevés dans des salinités proches de celle de Halk El Menzel ont été effectuées. Les résultats obtenus révèlent que la souche de Sabkhet Halk El Manzel n’appartient pas à l’espèce autochtone Artemia salina mais probablement à l’espèce invasive Artemia franciscana. The brine shrimp Artemia is perhaps the most conspicuous inhabitant of hypersaline biotope. The taxonomical study of the genus Artemia in the western Mediterranean region, including Italy, southern France, the Iberian Peninsula and Morocco, revealed the presence of the genus Artemia franciscana as an invasive specie. In this work, a new population of Artemia is reported for the first time from Sabkhet Halk El Menzel. A preliminary taxonomic identification of this population was realized on the one hand by a comparative study of the shape of the ovisac of females with five other Tunisian populations belonging to the Artemia salina specie and with the American Artemia franciscana specie from Great Salt Lake and on the other hand, morphological characteristics between adult samples harvested in situ from Sabkhet Halk El Menzel and five other Tunisian Artemia salina collected from sites showing approximately the same salinity. Statistical analysis was carried out using Principal Component Analysis and by Discriminant Function Analysis. The results obtained show that Artemia from Sabkhet Halk El Menzel does not belong to the native Artemia salina specie but probably to the invasive Artemia franciscana specie. However, it is important to mention that these results must be confirmed using other methods (Morphological study, genetic identification, biochemical characterization) for confirming the taxonomy of this population. Published Artemia, invasive specie, morphological characteristics, Tunisia.

L’étude de l’émission de carpospores de deux espèces de gracilaires : Gracilaria gracilis et de Gracilaria bursa-pastoris a été réalisée sur des fragments de thalle femelle à cystocarpes. Ces fragments ont été prélevés à différents niveaux de la plante mère (apex, parties intermédiaires et basales) reflétant un degré plus ou moins avancé de l’âge de la plante femelle à cystocarpes. Les différents fragments ont été exposés à des stress hydriques, thermiques et lumineux (intensité lumineuse et photopériode).Les résultats globaux ont montré que le nombre de carpospores émises sous une photopériode (12/12) est généralement supérieur à celui enregistré sous une plus courte photopériode (8/16), quelle que soit l’intensité lumineuse et la partie du thalle dont les fragments sont issus notamment chez la première espèce. Study of carpospore shedding of Gracilaria gracilis and Gracilaria bursa-pastoris was carried out on cystocarpic female gametophyte fragments. These fragments were picked up at different levels (apices; medium parties and basal ones), which reflect the degree of the age of the mother plant. The fragments were exposed to different stress (hydric, thermic and luminous: intensity and photoperiod). The global results showed that the maximum of spore release was generally obtained for 12/12 photoperiod whatever the origin of the fragments on the plant and the intensity of the irradiance and this for especially the first species. Published carpospores; Light.

دراسة التنوع البيولوجي للكائنات البحرية القاعية للشعب المرجانية « coralligène »للطابق « infralittoral » لقربص سمحت لنا للتعرف على ادنى مساحة نوعية لمثل هذه الدراسات التي تقام لاول مرة في تونس وتخص هذه الشعب. L’étude qualitative du coralligène enclavé de l’étage infralittoral de Korbous nous a permis de calculer son Aire Minimale Qualitative, ainsi que sa richesse spécifique. C’est la première étude de l’AMQ en Tunisie, et qui cible le peuplement du coralligène. The qualitative study of the coralligenous from the Infralittoral of Korbous allowed us to calculate its qualitative minimal area as well as its species richness. It is the first QMA study in Tunisia, focusing on coralligenous assemblages. Published