<> "The repository administrator has not yet configured an RDF license."^^ . <> . . . "The life-history ecology of Platycephalus bassensis\r\nand Nemadactylus macropterus"^^ . "The ecology of all life-history stages of two species of demersal fish, sand flathead\r\n(Platycephalus bassensis) and jackass morwong (Nemadactylus macropterus) found\r\nin coastal and continental shelf waters of southern and eastern Tasmania was\r\ninvestigated to determine the spatial and temporal patterns of spawning distribution\r\nand larval transport, recruitment, abundance and distribution, and size and age\r\ncomposition. The seasonal and interannual variations of the hydrography of shelf\r\nwaters are described and the influence of such variability on the life-history stages\r\nassessed.\r\nSpawning in P. bassensis occurred for an extended period of up to six months\r\nbetween October and March in estuaries, coastal embayments and shelf waters of\r\nsouthern and eastern Tasmania. The distribution of spawning fish, larvae and\r\npatterns of hydrography indicate that spawning on the shelf is primarily inshore.\r\nLarval development of P. bassensis is described. Larvae are concentrated in midwater\r\nwhich retain larvae inshore as cross-shelf subsurface currents are\r\npredominantly onshore.\r\nSpawning in N macropterus occurred between early January and late April in midand\r\nouter-shelf waters. Ichthyoplankton data indicate N macropterus larvae are\r\nconcentrated in surface waters, with few larvae caught during subsurface sampling of\r\nshelf waters over three years, despite large interannual differences in the extent of\r\nvertical mixing and stratification. The surface distribution of larvae appears to be a\r\nstrategy to maximise offshore transport as movement of surface waters of the shelf\r\nare generally offshore. However, large interannual variations in the influence of\r\nsubtropical and subantarctic waters on the shelf are described and the influence of\r\nsuch variations on larval transport assessed.\r\nSignificant seasonal and spatial variations in abundance of mature P. bass ens is were\r\nevident, the variations attributed primarily to the seasonal movement of fish between\r\nshelf and nearshore waters. Overlying the seasonal trends in abundance were\r\ninterannual variations that were at least au order of magnitude in difference. Mature\r\nP. bassensis were generally more abundant on the inner-shelf, with little evidence of\r\nsize-structuring with increasing depth. Settlement occurred over au extended period\r\nin summer with juveniles showing a strong preference for unvegetated habitats in nearshore waters, compared to beds of the seagrass, Heterozostera tasmanica.\r\nHowever, mature P. bassensis in nearshore waters showed no preference between\r\nvegetated and unvegetated habitats. There is evidence of a seasonal movement of\r\nthese nearshore fish out onto the shelf close to the size at maturity.\r\nIn contrast, N macropterus on the shelf showed size-structuring between depths and\r\nregions, with juveniles dominating the inner-shelf in both regions surveyed, while the\r\nmid- and outer-shelf of the east coast was dominated by mature fish. Settlement\r\nfrom the pelagic post-larval phase occurred in spring and early summer at between 7\r\nto 9 em and 9 to 12 months old. Storm Bay appears to be principally a nursery are;t\r\nfor the species with migration from the region occurring upon maturity. In addition,\r\nthe size-structuring by depth was one of the main factors attributed to the significant\r\nvariations in abundance across the shelf. Significant seasonal variations in\r\nabundance were also apparent, which is attributed to the seasonal movement of fish\r\nfrom south-eastern Tasmanian shelf waters.\r\nThe age, growth and spatial and interannual trends in age composition of\r\nP. bassensis and N macropterus were examined using transverse sections of sagittal\r\notoliths. The first annual increment was defined in both species by examination of\r\nthe progression of otolith radius and length of the 0+ cohort. Sex specific growth\r\ncurves are presented for both species. Maximum ages of P. bassensis was 17 years\r\nfor males and 13 for females, while N macropterus reached 41 years for males and\r\n30 for females. The age composition of both species was dominated by 4 to 7 years\r\nolds with considerable recruitment variability evident with a strong year-class in\r\n1986 for P. bass ens is and in 1988 for N macropterus. The relationship between the\r\nlife-history strategies of P. bassensis and N macropterus and recruitment variability\r\nis discussed."^^ . "1998-08" . . . . . "University of Tasmania"^^ . . . "ARRAY(0x7efd3a121fd8), University of Tasmania"^^ . . . . . . . . . "AR"^^ . "Jordan"^^ . "AR Jordan"^^ . . . . . . "The life-history ecology of Platycephalus bassensis\r\nand Nemadactylus macropterus (PDF)"^^ . . . . . . "jordon_front.pdf"^^ . . . "The life-history ecology of Platycephalus bassensis\r\nand Nemadactylus macropterus (PDF)"^^ . . . . . . "jordon_whole.pdf"^^ . . . "The life-history ecology of Platycephalus bassensis\r\nand Nemadactylus macropterus (Image (PNG))"^^ . . . . . . "preview.png"^^ . . . "The life-history ecology of Platycephalus bassensis\r\nand Nemadactylus macropterus (Image (PNG))"^^ . . . . . . "preview.png"^^ . . . "The life-history ecology of Platycephalus bassensis\r\nand Nemadactylus macropterus (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "The life-history ecology of Platycephalus bassensis\r\nand Nemadactylus macropterus (Other)"^^ . . . . . . "indexcodes.txt"^^ . . "HTML Summary of #16414 \n\nThe life-history ecology of Platycephalus bassensis \nand Nemadactylus macropterus\n\n" . "text/html" . .