Conservation of Anguilla anguilla, an endangered species: role of aquaculture in overcoming major bottlenecks

This thesis adopts a life-cycle-centric approach to European eel recovery, using aquaculture both as an experimental platform and as a conservation tool to improve “conversion efficiency” across key transitions in the species’ life cycle. By linking field observations and hatchery practices, premigratory phenotyping was refined through histology and gonadosomatic index combined with a calibrated eye-based screening method. Results showed that in productive North Adriatic lagoons, many SI III females already exhibit advanced ovarian development, shifting broodstock selection from rigid stage labels toward functional reproductive readiness. Under a standardized hormonal induction protocol, SI III females performed comparably to SI IV–V individuals in maturation timing, ovulation and spawning success, relative egg production, and viable egg and larval output. These findings extend the safe broodstock selection window when photothermal conditions and fat-to-ovary (FTO) thresholds are respected. Stock comparisons revealed complementary strengths: Comacchio females were larger and highly fecund, supporting scale-oriented production, whereas Orbetello females achieved higher floating-egg and hatching rates, favouring quality-oriented breeding strategies. On the male side, endocrine and functional markers informed fertilization design. Parentage analyses under pooled milt revealed strong paternity skew, motivating fractionated or sequential insemination, male rotation, and pre-fertilization sperm quality screening to preserve genetic diversity. A reproducible sperm cryopreservation protocol was also established, providing the foundation for a male-focused cryobank to synchronize gamete availability and buffer genetic drift in low-density systems. Preliminary larval trials indicated that partially alternative diets to the Japanese benchmark can sustain comparable growth and survival, provided that physical properties and lipid and peptide profiles are optimized. Finally, pop-up satellite tagging of phenotyped silver females confirmed migratory behaviour consistent with trans-Atlantic routes, validating the field-to-broodstock framework. Overall, this thesis presents an integrated blueprint linking phenotyping, controlled reproduction, cryobanking, larval nutrition, and telemetry into a continuum from lagoon to ocean, aligning aquaculture with conservation objectives.