The reproductive cycle of yellowfin bream, Acanthopagms australis (Günther), with particular reference to protandrous sex inversion

Abstract

Yellowfin bream, Acanthopagrus australis, of all age classes were collected from Moreton Bay, Australia. The species possessed typical sparid ovotestes in which the testis and ovary occur in separate zones. During the spawning period (June‐August) juveniles, functional males and functional females could be distinguished by the macroscopic appearance of the gonad. The sex ratio of males to females decreases with age, indicating protandrous sex inversion. Histological and structural study of the ovotestis showed all fish have previtellogenic cells in the ovarian zone but only juvenile and male fish have developing spermatogenic cells in the testis. Most juveniles become functional males by the age of two years but a small proportion of juveniles develop directly into functional females (primary females). Protandrous sex inversion commences after the spawning period when male fish appear with spermatozoa and no other spermatogenic cells in the testis. During the period November‐January male fish with no spermatogenic cells are common and a reduction in size of the testis occurs so that by March‐April the ovotestis becomes structurally and histologically similar to the female ovotestis. Some fish remain functional males during their whole life‐history (primary males). In functional females vitellogenic cells are present in the ovary only during the spawning period and the testis remains very small in size.

Spatial variation in demography of an estuarine teleost: implications for population and fishery assessments

“…This directly contrasts the situation for another estuarine sparid, A. butcheri, in which the fishery is dependent on the episodic recruitment of a couple of strong year classes (Morison et al 1998). These 2 species have different reproductive ecologies, with A. australis spawning in lower estuary and coastal environments and A. butcheri in the upper estuaries (Pollock 1985, Morison et al 1998.…”

“…The species is captured commercially using several active and passive gears, including beach seines, trawls, traps and gillnets across various fishery sectors. Hermaphroditism has been observed in the species (Pollock 1985), but the age and proportions of fish that change sex throughout the species range have not been quantified. Patterns of juvenile growth (Worthington et al 1992, Griffiths 2001 and that of adults (combined across genders) in the species' northern range (Pollock 1982) have been partially described.…”

Marine Stock Enhancement, Restocking, and Sea Ranching in Australia: Future Directions and a Synthesis of Two Decades of Research and Development

“…The lack of facilities or investment to hold sufficient numbers of broodstock, such as a nominal 100 effective breeders, may hinder the ability of commercial providers to produce fin-790 gerlings of appropriate genetic diversity for stock enhancement. In addition, the hermaphroditic protandry of some key species being considered for stock enhancement may further complicate broodstock management (e.g., Pollock, 1985). Some broodstock management problems, however, may be overcome through the 795 assistance of government or other research agency facilities and the development of broodstock "networks" among commercial providers, meaning that smaller numbers of broodstock are held by individual commercial providers and exchanged among these facilities for spawning events.…”

Effect of gonadotropin releasing‐hormone analogue and human chorionic gonadotropin on milt characteristics and gonadal steroids in yellowfin bream,Acanthopagrus australis(Sparidae)

“…The species has attracted attention as a candidate for aquaculture because of its marketplace acceptance, economic value, and ability to withstand wide variations in salinity and temperature (Thorogood 1991;Thorogood & Blackshaw 1992;Cowden 1995;Battaglene & Fielder 1997;Allan & Fielder 1999;Taylor et al 2005). Yellowfin bream are serial spawners, spawning many times during a single season with a peak spawning period occurring between July and August (Pollock 1982(Pollock , 1984(Pollock , 1985. Currently, there is no information available on the effects of exogenous hormones for enhancement of spermiation among captive brood fish of yellowfin bream to ensure adequate milt production for repeat spawnings.…”