Induction of sexual maturation in wild female European eel (Anguilla 1 anguilla)in darkness and light conditions

The aim of present study was to induce sexual maturity in wild silver eels females of the European 19 eel using a protocol similar to the one already successfully used for Anguilla japonica. Weekly 20 injections (n. 16) of carp pituitary extracts (CPE) with an increasing dose of 10, 20, 30 and 40 21 mg/kg BW were given to silver females kept in light (L-Group) or dark (D-Group) conditions. In both 22 groups, the final oocyte maturation and ovulation was induced by injection of 17,20 h-dihydroxy-4-23 pregnen-3-one (DHP) at 2 mg/g BW. All the eels turned out to be silver and actively migrant (n 58 24 in stage V and n 2 in stage IV), showing a particularly high EI (15.75±1.40) and they were 25 distributed within 3 age classes (7-9 years). In D-Group one of the 4 females at 13th CPE treatment 26 ovulated 12h after the DHP injection. The remaining 3 females, which received the final (16th) CPE 27 injection, ovulated between 12 and 36 h after the DHP injection. Two out of the 4 L-Group females 28 which received the 16th CPE injection ovulated between 12 and 36 h after the DHP injection and the 29 remaining 2 (L14 and L16) did not ovulate within 36 h post DHP injection. The total number of eggs 30 released by the D-Group (n. 1,485,600) was significantly higher than that of the L-Group (n. 31 274,000). No mortality was observed during the experiment.