Producing flat-head grey mullet Mugil cephalus (Linnaeus, 1758) fries in captivity from sexually mature adults collected in Sardinian lagoons

Mugil cephalus has been identified as a suitable species for feeding populations in developing countries, and it represents a traditionally harvested and consumed species in various European countries. A decline in wild populations and a growing demand have promoted new interest in mullet production in hatcheries, considered imperative for the production of a steady supply of fry and the expansion of M. cephalus aquaculture. In the present study, wild adults collected in Sardinian lagoons were induced to spawn during their natural reproductive period by treating them with a single dose of a slow release GnRHa preparation (200 µg kg bw). In 2016, a protocol for reducing stress in capturing, transporting and selecting wild adults was set up, and 64% of the females with an oocyte diameter larger than 550 µm were successfully induced to spawn. Five spawning induction trials were carried out in the period 2016-2019. The mean fertilization rate and the mean hatching rate obtained were 83 ± 14% and 76 ± 13%, respectively. The individuals obtained were reared indoor in a recirculating aquaculture system (RAS) at a density of 40 individuals L for 60 days, and their survival ranged from 10 ± 2 to 19 ± 1%. During the whole larval rearing phase, from 0 to 34 days post hatching (dph), the mean standard growth rates recorded were 5.0 ± 0.7% in total length and 14.4 ± 3.9% in body weight. The rearing density used resulted in an average survival rate comparable or even better than those obtained by other authors, thus indicating the possibility of producing M. cephalus fries in captivity from sexually mature adults captured in Sardinian lagoons, reducing the costs and optimizing the production.