Abstract
The greater amberjack Seriola dumerili is a large teleost fish with rapid growth and excellent flesh quality, whose domestication represents an ambitious challenge for aquaculture. The occurrence of reproductive dysfunctions in greater amberjack reared in captivity was investigated by comparing reproductive development of wild and captive-reared individuals. Wild and captive-reared breeders were sampled in the Mediterranean Sea during three different phases of the reproductive cycle: early gametogenesis (EARLY, late April-early May), advanced gametogenesis (ADVANCED, late May-early June) and spawning (SPAWNING, late June-July). Fish reproductive state was evaluated using the gonado-somatic index (GSI), histological analysis of the gonads and determination of sex steroid levels in the plasma, and correlated with leptin expression in the liver and gonad biochemical composition. The GSI and sex steroid levels were lower in captive-reared than in wild fish. During the ADVANCED period, when the wild greater amberjack breeders were already in spawning condition, ovaries of captive-reared breeders showed extensive atresia of late vitellogenic oocytes and spermatogenic activity ceased in the testes of half of the examined males. During the SPAWNING period, all captive-reared fish had regressed gonads, while wild breeders still displayed reproductive activity. Liver leptin expression and gonad proximate composition of wild and captive greater amberjack were similar. However, the gonads of captive-reared fish showed different total polar lipid contents, as well as specific lipid classes and fatty acid profiles with respect to wild individuals. This study underlines the need for an improvement in rearing technology for this species, which should include minimum handling during the reproductive season and the formulation of a specific diet to overcome the observed gonadal decrements of phospholipids, DHA (22:6n-3) and ARA (20:4n-6), compared to wild breeders.
Highlights
European consumer demand for more/new seafood products has been increasing over the last decade [1]
The objective of the present study was to identify the occurrence of the common reproductive dysfunctions during gametogenesis in greater amberjack caught as juveniles from the wild and reared to sexual maturity in captivity, through the comparative analysis of reproductive development during different times of the reproductive season
Female gonado-somatic index (GSI), gonad histological analysis and sex-steroid plasma levels. In both wild and captive-reared individuals, GSI values showed a significant increase from the Early Gametogenesis (EARLY) to the ADVANCED phase, and a significant decrease during SPAWNING (Fig 1)
Summary
European consumer demand for more/new seafood products has been increasing over the last decade [1]. The greater amberjack Seriola dumerili (Risso, 1810) is a large coastal epibenthic and pelagic teleost fish with a wide geographical distribution, which includes the Indo-West Pacific Ocean [6], the Western Atlantic Ocean [7, 8], the Eastern Atlantic Ocean (from British to Moroccan coasts) and the Mediterranean Sea [9] It is a gonochoric species with group-synchronous ovarian development and a multiple spawning pattern [10, 11], with a reproductive season between late spring to early summer in the Mediterranean region, and between later spring and early autumn in the Eastern Atlantic Ocean [12]. The absence of a significant aquaculture industry for greater amberjack in Europe is testament to the lack of a reliable technology for broodstock management and reproduction control in captivity for this species [26]
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