Seascape connectivity of European anchovy in the Central Mediterranean Sea revealed by weighted Lagrangian backtracking and bio-energetic modelling

Ecological connectivity is one of the most important processes that shape marine populations and ecosystems, determining their distribution, persistence, and productivity. Here we use the synergy of Lagrangian back-trajectories, otolith-derived ages of larvae, and satellite-based chlorophyll-a to identify spawning areas of European anchovy from ichthyoplanktonic data, collected in the Strait of Sicily (Central Mediterranean Sea), i.e., the crucial channel in between the European and African continents. We obtain new evidence of ecosystem connectivity between North Africa and recruitment regions off the southern European coasts. We assess this result by using bio-energetic modeling, which predicts species-specific responses to environmental changes by producing quantitative information on functional traits. Our work gives support to a collaborative and harmonized use of Geographical Sub-Areas, currently identified by the General Fisheries Commission for the Mediterranean. It also confirms the need to incorporate climate and environmental variability effects into future marine resources management plans, strategies, and directives

Comparative characterization of the spawning environments of European anchovy, Engraulis encrasicolus, and round sardinella, Sardinella aurita (Actinopterygii: Clupeiformes) in the eastern coast of Tunisia

Background. The distribution of early ontogenic stages of small pelagic fishes is important for understanding the dynamics of their fluctuating populations. To fill a gap in the knowledge we conducted a comparative analysis on the distribution of eggs and larvae of the exploited populations of European anchovy, Engraulis encrasicolus (L.) and round sardinella, Sardinella aurita (Valanciennes, 1847), in the eastern coast of Tunisia. Materials and methods. A multidisciplinary survey was carried out in the summer of 2008, from June 23 through July 9. Samples were taken over a grid of 71 stations. Temperature and salinity profiles were recorded at each station by CTD casts and water samples were taken by means of a Rosette equipped with Niskin bottles. Ichthyoplankton was sampled by oblique tows with a Bongo net of 60 cm mouth diameter and 335-µm mesh nets. To specify the preferred spawning environment the quotient values were estimated for each variable. Results. The eggs and larvae of both species represented an important proportion of the ichthyoplankton, around 50% for each ontogenic stage. Anchovy mainly spawned in the shelf edge, north-east of Kuriate Island, with a minor spawning area near Cap Bon and Kelibia. The main spawning area of the round sardinella was in the warmer waters. It was located near the major spawning ground of anchovy. Anchovy eggs were scarce in the coastal zones and in the south of the study area, whereas round sardinella eggs were scarce in the north. The main spawning grounds of anchovy coincided with the area of higher zooplankton abundance while round sardinella spawning grounds correspond with those areas of highest chlorophyll-a and zooplankton. This distribution suggests a propensity for food availability, for both adults and larvae, as the location of spawning grounds of these species. Conclusion. Both anchovy and sardinella spawned mainly in deeper waters within the limits of the continental shelf. Each species appeared to have a specific strategy for spawning that was influenced by physical and biological variables

Preparation of n.c.a. 6-[18F]fluoro-L-tryptophan using copper-mediated radiofluorination

Preparation of n.c.a. 6-[18F]fluoro-L-tryptophan using copper-mediated radiofluorinationObjectives: The essential amino acid tryptophan is involved in various physiological processes. Besides protein synthesis, tryptophan is the precursor for serotonin and kynurenine. An upregulated utilization of tryptophan in tumor cells was reported (1). The degradation product kynurenine was described as an important factor in tumor growth and immune suppression (2). Accordingly, labelled tryptophan could enable to trace alterations of tryptophan uptake in regions of serotonergic neurons (3). Until now, [18F]fluorotryptophan was labelled using the Balz-Schiemann reaction (4) providing insufficient radiochemical yields. A recently published isotopic exchange reaction (5) appears to engender challenges in automation that are preventing their routine use. In the last few years, several innovative 18F-fluorination methods have been published (6-8). The copper-mediated radiofluorination method exhibits several major advantages like sufficient RCYs, bench-stable precursors and mild reaction conditions and was therefore chosen in this study. First, the synthesis of an appropriate aryl boronic ester was developed. The labelling step and hydrolysis were optimized with regard to automation.Methods: An appropriate precursor for 18F-labelling was designed starting from bromo-indole. The Schöllkopf’s auxiliary (9) was introduced within five steps. The pinacol boronate ester was inserted using a Suzuki-Miyaura coupling reaction. Figure 1: Synthesis scheme for the pinacol ester tryptophan derivative 3.In preliminary studies indole derivatives with the pinacol ester in different position were used as model compounds. The highest yields were obtained at 6-position of the indole motif. Besides reaction time and temperature, different reaction conditions like the type of nucleophilicity enhancer, temperature, time and solvents were examined. The subsequent deprotection step was optimized with regard to acid, reaction time and temperature. Figure 2: Radiosynthesis of 6-[18F]fluoro-L-tryptophan.Results: The synthesis of the appropriate precursor for copper-mediated radiofluorination was achieved within six steps and an overall yield of 37 %. The optimized radiofluorination conditions are as follows: precursor and Cu(OTf)2(py)4 were solved in sulfolane/acetonitrile were given on dried tetraethylammonium [18F]fluoride (TEA[18F]F) and heated for 20 min at 110 °C. The radiochemical conversion (RCC) protected [18F]4 was 52±10 % determined by radioTLC. Purification of [18F]4 from residual [18F]fluoride and copper was achieved by using a silica cartridge. Highest RCC for deprotection yields were obtained using 48 % hydrobromic acid for 25 min at 165°C giving 36.1±5 % RCC.The total radio synthesis of 6-[18F]fluoro-L-tryptophan was carried out within 120 min including HPLC purification (Figure 3) with an overall radiochemical yield of 13±4 %. The radiochemical purity was more than 99 %, with an enantiomeric excess of 89 % and a specific activity of 280 GBq/µmol. Automation of the reaction as well as the biological evaluation of the radiotracer is in progress. Figure 3: Radioanalysis of HPLC purified 6-[18F]fluoro-L-tryptophan.Conclusion: The herein reported method allows to obtain n.c.a. 6-[18F]fluoro- L-tryptophan in high RCYs. Accordingly, the potential of this tracer could be evaluated in different applications like tumor detection or psychological disorders. Furthermore, an automated synthesis unit equipped with a two-reactor-system is in progres

Engraulis encrasicolus (Linnaeus, 1758)egg and larval distribution in the eastern coast of Tunisia in relation to environmental characteristics

An ichthyoplankton survey was conducted on the eastern coast of Tunisia from the 10th to 18th August 2004 with the investigation of 68 stations. The sampling period corresponded to stratified summer conditions, with average SST 26.97°C. The thermocline was found between 25 and 50 m depth. The eastern coast of Tunisia was influenced by the water exchanges between the eastern and western Mediterranean. Anchovy eggs and larvae were a major component of the ichthyoplankton, representing 26 and 19% of the total mean fish egg and larval abundances, respectively. Their mean abundances were 108 eggs.10 m-2 and 112 larvae.10 m-2. The spawning areas were mainly located off the 100 m isobaths, with the maximum abundance occurring near the shelf break, as opposed to the inshore waters where anchovy eggs and larvae were practically absent. Depth was the main factor controlling the distribution of anchovy eggs and larvae. Larval transport from the spawning areas is made evident following southward to south-eastward directionsPublicado

Neither azeotropic drying, nor base nor other additives: a minimalist approach to F-18-labeling

A novel, efficient, time-saving and reliable radiolabeling procedure via nucleophilic substitution with [F-18] fluoride is described. Different radiolabeled aliphatic and aromatic compounds were prepared in high radiochemical yields simply by heating of quaternary anilinium, diaryliodonium and triarylsulfonium [F-18] fluorides in suitable solvents. The latter were obtained via direct elution of F-18(-) from an anion exchange resin with alcoholic solutions of onium precursors. Neither azeotropic evaporation of water, nor a base, nor any other additives like cryptands or crown ethers were necessary. Due to its simplicity this method should be highly suitable for automated radiosyntheses, especially in microfluidic devices

Larval fish community composition and distribution of the central-southern Mediterranean under summer and winter conditions

Background. The Gulf of Gabès supports an important fishery which is characterized by a great diversity of fish species. Despite this importance, there has been no attempt to examine the whole larval fish assemblage in this area. The aim of this study was to investigate the larval fish communities during summer and winter seasons in the Gulf of Gabès. Materials and methods. Two multidisciplinary surveys were carried out aboard the R/V Hannibal in 2009. A total of 80 and 70 stations were sampled during winter and summer surveys, respectively. Stations were arranged in a regular sampling grid of 10 × 10 nautical miles. Ichthyoplankton was sampled by oblique tows with a Bongo net of 60 cm mouth diameter, fitted with 335 µm mesh nets. Zooplankton dry weight was obtained by drying aliquots of the zooplankton sample in an oven at 60ºC, for 72 hours. Results. In summer 34 taxa representing 24 families, were collected, whereas in winter 35 taxa, representing 16 families, were collected. Larval fish communities were dominated by small pelagic species: sardinella and anchovy in summer and sardine in winter. The results also highlight the Gulf of Gabès as an important spawning ground for many large and medium pelagic fishes, both highly migratory (Thunnus thynnus) and resident species (Auxis rochei, Euthynnus alletteratus). The summer/winter differences observed in species composition and abundance of the larval fish communities reflected the seasonality in fish species spawning in the Mediterranean Sea, likely influenced by the highly contrasting environmental conditions between seasons. Thus, the seasonal changes in the hydrographic conditions of the Gulf of Gabès result in different scenarios that provide suitable spawning environments for a variety of fishes, allowing them to share the Gulf as spawning habitat. Conclusion. The Gulf of Gabès is an important fish spawning area for demersal, small pelagic, medium pelagic, and large pelagic (tunas). Larval species composition differed considerably between summer and winter surveys

Distribution of tuna larvae in Tunisian east coasts and its environmental scenario

Early life stages of tuna species were investigated along the Tunisian east coast during the summer of 2008 by means of a larval survey conducted on board the R/V HANNIBAL. In this study we define the spawning grounds of tuna fishes in Tunisian waters and relate the tuna larvae spatial distribution to the hydrographic features and other environmental parameters. A total of 282 larvae of Atlantic bluefin tuna (Thunnus thynnus, Linnaeus, 1758), 902 of bullet tuna (Auxis rochei, Risso, 1810) and 19 of little tuna (Euthynnus alletteratus, Raf, 1810), were identified. High larval concentrations of bluefin tuna were located offshore (mean = 200 ± 18 m), at sea surface temperatures ranging between 23.7 to 25.3°C, whereas the highest concentrations of bullet and little tuna were located in shallower waters (mean = 135 ± 75 m), at sea surface temperature ranging between 25.1 to 25.9°C. According to their preference for waters with surface salinities ranging between 37.1 and 37.8, spawning of these species seems to occur mainly in mixed waters. Stations where tuna larvae were collected showed oxygen concentrations between 6.55 and 6.85 mg l-1, as well as low turbidity and chlorophyll a values, from 0.2 to 0.5 NTU a d less than 1 mg m-3, respectively. These three environmental factors were weakly correlated with tuna larvae abundancePublicado

Copper-mediated aromatic radiofluorination revisited: Efficient production of PET tracers on a preparative scale

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim