| Summary: | [EN] The European eel (Anguilla anguilla) is a species with high aquaculture interest worldwide and with a high production in the context of European aquaculture. However, eel fish farming is presented as an unsustainable activity over time, mainly due to the fact that companies depend on the supply of juveniles from the natural environment. In addition, it is currently listed as a critically endangered species (IUCN) due to the drastic reduction in its population in recent decades. Therefore, the captive reproduction of this species is presented as a key element for its conservation, which will help reduce the pressure on natural populations, facilitate the supply of eel farms, and allow repopulation in areas where historically the eel was found. The objective of the present study was to evaluate the application of alternative methods of induction of sexual maturation (controlled release systems, CRS) in female European eels. In order to develop protocols capable of inducing ovulation in European eel, the evaluation was carried out both in biological and economic terms. The results show that the implantation of osmotic pumps induced maturation in 80% of the females, reducing the duration of hormonal treatment in 50% of them, which reached maturation in the first 4-10 weeks of treatment. Regarding the evolution of the weight of the females during maturation, an increase in the previous week of 16±6% in the OP-2ML4 group and 20±14% in the control group. Regarding the gonadosomatic index (GSI), the females implanted with osmotic pumps presented similar values to the control group, 49.5±2.8% and 51.2 ± 9.8%, respectively. Likewise, a total of 6 clutches were obtained, reaching the embryo state formed with distinguishable head, eyes and somites as maximum embryonic development. Finally, this study shows that the use of osmotic pumps loaded with carp pituitary extract (CPE) is an effective method to induce sexual maturation in female European eels, generating early maturations (weeks 4-10) in 50% of females with an ...
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