Relations between migration, reproduction and nutrition in yellowfin bream Acanthopagrus australis

Abstract

The yellowfin bream Acanthopagrus australis (Giinther) is an estuarine species in which a large proportion of the adult population does not participate in the annual seaward spawning migration. Monthly samples of migratory and non-migratory yellowfin bream were collected from March to October 1982. Measures of gonad and oocyte development and 3 indices of nutritional state (feeding index, visceral fat index and condition factor) were obtained for each fish sampled. Gonads developed to a similar size in migratory and non-migratory adults. Successful reproduction, as indicated by the presence of hyaline-stage oocytes, only occurred in migratory fish. In non-migratory females oocytes developed to the yolk-stage, but then became atretic and were resorbed. In both groups stored energy reserves decreased as the gonads increased in size; however the rate of decrease was greater in migratory fish. Feeding almost ceased in migratory fish during the spawning period (May to Aug) because suitable food items (benthic animals and plants) are uncommon in the spawning areas. In non-migratory fish, feeding was reduced during the late spawning period, possibly because abundant energy reserves were available due to oocyte resorption. An examination of sex ratios within age classes indicated a decreasing tendency of females to participate in the spawning migration with age. All male fish older than age I1 participate in the spawning migration. The seasonal patterns of gonad development and nutritional state associated with the spawning migration of yellowfin bream are similar to those reported for other teleost fishes. These patterns have not been documented for the non-migratory component of other teleosts which have annual spawning migrations.

Demography of a large grouper, Epinephelus fuscoguttatus, from Australia’s Great Barrier Reef: implications for fishery management

“…Insufficient energy reserves, stress, or unsuitable environmental conditions may also cause fish to miss spawning in some years. For example, older females of an Australian sparid, Acanthopargus australis, had a low tendency to participate in seaward spawning migrations, possibly due to insufficient energy reserves to migrate and spawn (Pollock 1984).…”

Infection of the kidney of Acanthopagrus australis (Pisces:Sparidae) with Sphaerospora sp. (Myxosporea), Prosorhynchus sp. (Digenea), and cysts of unknown origin

“…Fish were assigned to age classes based on the studies of age and growth of Acanthopagrus australis in Moreton Bay by Pollock (1984). Age classes (cm) were defined as follows: Q+, SL 14.5; ?+, 14.5 I SL 2 18.4; 2+, 18.5 I SL < 21.1; 3+ (and older), SL > 21.1 cm.…”

“…The yellowfin bream has an ovo-testis and undergoes protandrous sex inversion at about 3 yr old (Pollock 1984). Most male and young female bream migrate from the summer grounds in western Moreton Bay to spawn at the surf bars on the eastern side of the bay in winter (Pollock 1982).…”

Panmictic population structure in the migratory marine sparid Acanthopagrus australis despite its close association with estuaries

“…Spawning behaviour is relatively unstudied in A. australis, although spawning is thought to occur in entrance channels or lower reaches of coastal lakes and lagoons ('estuaries') or in the surf zone of beaches adjacent to the entrances of estuaries (Pollock 1982b(Pollock , 1984. This close association with estuarine spawning sites has the potential to promote fine-scale genetic differentiation of both adult and juvenile populations if A. australis lineages maintain prolonged associations with individual estuaries.…”