The European eel (Anguilla anguilla), once abundant throughout much of Europe and North Africa, has recently been classified as critically endangered. Information on its biology from the eastern Mediterranean is lacking, especially in relation to spawner quality. Therefore, silver eels were sampled during their seaward spawning migration from Vistonis Lake in Greece. Characteristics linked to reproductive output and success (i.e. body size and condition, sex ratio, silvering, Anguillicola crassus infection, fecundity and oocyte diameter) were examined. The lake produced large (687-1138 mm), exclusively female silver eels, 61.7% of which were infected by A. crassus. Silver eel fecundity, the first estimates from the southern part of the species range, was positively related to body length (R 2 = 0.693; P < 0.001) and body weight (R 2 = 0.731; P < 0.001). Fecundity did not differ between A. crassus infected and uninfected silver eels, but Greek silver eels were significantly more fecund than those in northwest Europe. The reproductive potential of Vistonis Lake silver eels and their contribution to the A. anguilla spawning stock is discussed.
III Agraïments Estem a primers dels 2008. Abans de tancar aquesta etapa i proposar-me nous reptes no puc deixar de mirar enrera i recordar l'immens suport que he rebut de tantíssimes persones. Entre tots heu contribuit a donar forma a aquest projecte i aquestes línies volen fer-vos arribar el meu profund agraïment i la gran satisfacció em queda de què m'hagueu acompanyat durant aquesta llarga travessia. Començo pels meus directors. La Míriam em va iniciar en les ciències socials quan ens vam conèixer en el projecte Eurosion. Gràcies a la seva presència des del bon principi i al seu paper més enllà de lo professional, és en gran part la responsable de què hagi arribat a bon port. El David amb el seu entusiasme i les ganes d'innovar ha sigut un bon estímul. El finançament de la recerca no ha faltat mai gràcies als següents projectes i institucions:
Biodiversity is a key factor for the functioning and efficiency of an ecosystem. Greece, though covering a relatively small surface area, hosts a great deal of species diversity. This is especially true for freshwater fishes. In recent years, the traditional methods of species identification have been supplemented by the use of molecular markers. The present study therefore aims to extensively produce DNA barcodes for Greek freshwater fish species and investigate thoroughly if the presently accepted species classification is in agreement with molecular data. A 624-bases long fragment of the COI gene was sequenced, from 406 freshwater fish specimens belonging to 24 genera and originating from 18 lake and river sites. These sequences were used along with 596 sequences from the same genera, recovered from BOLD, for the construction of phylogenetic trees and the estimation of genetic distances between individuals. In total, 1002 sequences belonging to 72 species were analyzed. The method was found to be effective for 55 of 72 studied species. 17 closely related species with low interspecific genetic distances were observed, for which further study is proposed. It should also be noted that, in four cases, cryptic diversity was observed, where groups originally identified as one species exhibited genetic distance great enough to be separated into discrete species. Region specific haplotypes were also detected within populations of 14 species, giving the possibility to identify even the geographic origin of a species. Our findings are discussed in the light of the rich history of the Balkan peninsula and provide a significant steppingstone for the further study of Greek and European freshwater fish biodiversity.
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