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Chthamalus antennatus occurs on the Australian mainland between Double Island Pt. (Qld) and somewhere west of Pt. Sinclair in the Great Australian Bight. The species is most abundant on smooth surfaced rock platforms that are moderately exposed to oceanic waves. In these localities it is associated with a down shore zone of the barnacle T. rosea (Qld. northern N.S.W), or C.columna (southern N.S.W. and S.A.) or the mussell Branchydontes rostratus (Vic). The northern limit of the species may be due in part to a southerly current off the southern Queensland coast carrying larvae further south. A preliminary study using numerical analysis techniques was undertaken to look at the relative importance and effects of co-acting factors on the Chthamalus zone at Cylinder Headland, Pt. Lookout. Selected abiotic and biotic attributes were subjected to ordination and classification programs and the attribute combinations most important in defining groups were assessed. C.antennatus has an annual breeding cycle. Fertilization occurs about December and nauplii appear to develop in the mantle cavity until November of the next year when they are released into the plankton. Between 1972-1974 there was no recruitment of C.antennatus to the shore at Pt. Lookout. Although C.antennatus is restricted to a high shore zone through out its geographic range it can grow and survive at higher and lower shore levels. Transplantation experiments at Pt. Lookout showed that low on the shore C.antennatus could grow faster but mortality also increased. High on the shore growth rate was reduced and mortality increased. The length of the opercular diameter was shown to be a useful parameter in estimating the body size of C.antennatus. The effects of sand movements on community structure at Pt. Lookout are discussed.
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