Increased melanomacrophage centres in the liver of reproductively dysfunctional female greater amberjack Seriola dumerili (Risso, 1810).

The greater amberjack Seriola dumerili is a new aquaculture fish that may display reproductive dysfunctions. During extensive follicular atresia, which is a common reproductive dysfunction in females during vitellogenesis, part of the reabsorbed yolk returns to the liver to be metabolized and recycled. Melanomacrophage centres (MMCs) are aggregates of macrophage-like cells that play a role in the destruction, detoxification and recycling of endogenous and exogenous materials, and have been associated with systemic stress. Wild and captive-reared greater amberjack were sampled in the Mediterranean Sea during two different phases of the reproductive cycle. The liver of reproductively dysfunctional captive-reared females sampled during the spawning season showed a high density of both MMCs and apoptotic cells. A weak liver anti-cytochrome P450 monooxygenase 1A immunoreactivity was observed, suggesting that the examined fish were not exposed to environmental pollutants. We propose that the observed increase in MMCs and apoptosis in captive-reared fish was related to the hepatic overload associated to the metabolism of yolk proteins reabsorbed during extensive follicular atresia. Since follicular atresia is a frequent physiological and pathological event in teleosts, we suggest that the reproductive state should be always assessed when MMCs are used as markers of exposure to stress or pollutants.

An Observational Study of Skeletal Malformations in Four Semi-Intensively Reared Carp Species.

Cyprinids include some of the most widely farmed freshwater species. The aim of this study was to assess the incidence of skeletal malformations in carp species reared in semi-intensive systems in Albania: common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix), grass carp (Ctenopharyngodon idella) and bighead carp (Hypophthalmichthys nobilis). The common carp fingerlings had a mean total length of 28.9 ± 5.0 mm; the frequencies of individuals with at least one anomaly and at least one severe anomaly were 79.2% and 43.4%, respectively. The silver carp juveniles had a mean total length of 21.6 ± 2.1 mm; the frequencies of individuals with at least one anomaly and one severe anomaly were 93.1% and 57.5%, respectively. The grass carp fry had a mean total length of 33.5 ± 2.6 mm; all the analyzed specimens showed almost one anomaly and 86.4% showed at least one severe anomaly. The bighead carp juveniles had a mean total length of 34.4 ± 5.7 mm; the frequencies of individuals with at least one anomaly and at least one severe anomaly were 95.0% and 62.5%, respectively. The development of a more suitable feeding protocol for herbivorous species and the setting up of more efficient broodstock management protocols are suggested to reduce the high incidence of skeletal malformations.

Reproductive Maturation of Meagre Argyrosomus regius (Asso, 1801) Reared in Floating Cages.

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.