Citation: Zupa, R.; Hala, E.; Ventriglia, G.; Pousis, C.; Passantino, L.; Quaranta, A.; Corriero, A.; De Virgilio, C. Reproductive Maturation of Meagre Argyrosomus regius (Asso, 1801) Reared in Floating Cages. Animals 2023, 13, 223. https:// doi.org/10.3390/ani13020223 Academic Editors: Beata Irena Cejko, Agata Kowalska and Roman Kujawa Received: 6 December 2022 Revised: 3 January 2023 Accepted: 4 January 2023 Published: 7 January 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). animals Article Reproductive Maturation of Meagre Argyrosomus regius (Asso, 1801) Reared in Floating Cages Rosa Zupa 1 , Edmond Hala 2 , Gianluca Ventriglia 1 , Chrysovalentinos Pousis 1 , Letizia Passantino 3 , Angelo Quaranta 1 , Aldo Corriero 1, * and Caterina De Virgilio 4 1 Department of Veterinary Medicine, University of Bari Aldo Moro, 70010 Valenzano, Italy 2 Department of Animal Production, Faculty of Agriculture and Environment, Agricultural University of Tirana, 1030 Tirana, Albania 3 Department of Precision and Regenerative Medicine and Ionian Area, Section of Veterinary Clinics and Animal Production, University of Bari Aldo Moro, 70010 Valenzano, Italy 4 Department of Biosciences, Biotechnologies and Environment, University of Bari Aldo Moro, 70124 Bari, Italy * Correspondence: aldo.corriero@uniba.it Simple Summary: The meagre (scientific name: Argyrosomus regius) is a fish species inhabiting the Mediterranean Sea and the eastern Atlantic Ocean. Consumer appreciation and good market quotations induced the aquaculture industry to invest in its domestication. However, when reared in tanks, meagre males produce milt of low quality and quantity, and females do not finalise oogenesis and do not spawn spontaneously. The reproductive dysfunctions affecting meagre reared in tanks, can be alleviated through the use of hormone administration or through the association of hormone treatments with photo-thermal control. In this study, the reproductive maturation of meagre, reared in sea cages under routine farming condition, was assessed. It was observed that female and male meagre produced in captivity (hatchery), transferred as juveniles to sea cages located in the Gulf of Taranto (Italy), and reared until sexual maturity under routine commercial conditions, are able to produce and release gametes spontaneously. Meagre reproduction, under routine farming conditions, may represent an opportunity for the expansion of meagre EU aquaculture production; this actually relies on limited amounts of fingerlings, produced by few hatcheries. Abstract: The meagre Argyrosomus regius (Asso, 1801) is a promising aquaculture species that shows reproductive dysfunctions when reared in tanks. The aim of this study was to assess the capacity of meagre, reared in cages under routine farming conditions, to mature gonads and reproduce spontaneously. Meagre adults, reared in a fish farm located in the Gulf of Taranto (Italy), were sampled from March to July 2021. The gonadosomatic index and sex steroid plasma concentrations increased from March–April to June, and then decreased in July. In March–April, most of the females showed perinucleolar or cortical alveoli oocytes as the most advanced stages in the ovaries, and most of the males had testes at early spermatogenesis stage. In June, most of the sampled females had oocytes at late vitellogenesis or early post-vitellogenesis stages, and males had seminiferous tubules filled with spermatozoa. In July, most of the females had signs of previous spawning, and males showed scarce amounts of luminal spermatozoa. The present study demonstrated the capacity of meagre, reared in sea cages under commercial conditions, to carry out gametogenesis and spontaneously release gametes. Meagre reproduction, under routine farming conditions, may represent an opportunity for the expansion of meagre aquaculture production. Keywords: broodstock management; reproduction in captivity; fish oogenesis; fish spermatogenesis; fish reproduction 1. Introduction The meagre Argyrosomus regius (Asso, 1801) is a promising niche species that is increas- ingly appreciated by consumers [1], and whose EU fishery and aquaculture production Animals 2023, 13, 223. https://doi.org/10.3390/ani13020223 https://www.mdpi.com/journal/animals