URERA

The cryptogenic grapsid crab Pachygrapsus maurus (Lucas, 1846), is a native species in the Mediterranean Sea that has been reported since the 1990s in several parts of the central basin such as the Maltese islands and Italian coast. However, the species presence in the areas such as eastern Algeria, Tunisia and Libya has not been documented previously. In September 2016, a preliminary survey was carried out to investigate the marine biodiversity in the channel of Bizerte (Northern Tunisia), during which P. maurus was observed and documented. Individuals were captured, photographed and identified based on key morphological features. The number of individuals observed indicates the species is well-established within the specialized rock and boulder habitat with strong wave exposure preferred by this species.

With its 1300 km coastline and 110 000 ha of coastal lagoons, Tunisia offers important resources to demersal and pelagic fisheries. Among all the exploited fish species in Tunisia, mugilids are the most widespread. They are known in temperate, subtropical and tropical regions, and occur both in coastal areas, lagoon ecosystems and inland waters. Six mugilids species have been inventoried in Tunisia. Their migratory behavior consists of moving back and forth between brackish and saline environment where they spend a large part of their life cycles. This behavior results in a peculiar high vulnerability to human pressure. Consequently, they require special attention from fisheries managers for sustainable catches. This study was based on the data from the national fishing and aquaculture directorate (DGPA) statistics, and comprised time series from 1995 to 2015. We looked for clear tendencies and correlations between harvest from the coastal sea and lagoons of the different coastal re...

The present study reports the capture and recording of an individual of the tripletail fish Lobotes surinamensis in Esquerquis Bank (northern Tunisia) in February 2017. In Tunisia, it is the first record of the Herculian species in northern deep waters (around 200 meters) after the latest observation of L. surinamensis in 2015 from the coastal water. These reports of the Herculean species, chronologically closer together, lead us to believe that the species was established in the Tunisian waters.

Fish trophic structure of the Ichkeul Lake (northern Tunisia, southern Mediterranean) was studied to determine principal preys and consumers as trophic links between them that allows characterization of the food web structure. To realize this purpose, two complementary approaches were performed; stable isotopes ratios of carbon and nitrogen were used as trophic tracers, while stomach content analysis was used to determine ingested preys by fishes. The first method was applied to fishes, invertebrates and primary producers were analyzed in both wet and dry seasons and in two marked areas of the site study, eastern area (with more marine tendency) and western area (with more lacustrine tendency). The second method was concerned only consumers namely fishes.

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, Rup- pia cirrhosa) and water brackish algae (Ulva spp. and Chaetomorpha spp., Cladophora sp., Polysiphonia sp.).