General features of the ecology and biogeography of Tasmanian subtidal rocky shore communities

A number of subtidal benthic assemblages of plants and animals which commonly occur around the Tasmanian coast are described. These assemblages are incorporated into a general scheme which relates subtidal zonation patterns to wave exposure and depth. The existence of a cool-temperate marine biogeographic province (the Maugean), centred in southern, western and eastern Tasmanian waters, is reaffirmed. The biota of the northern Tasmanian coast is considered similar to that of the Victorian coast and includes a large component of Flindersian (Southern Australian) species. A number of Peronian (New South Wales) species reach the Tasmanian east coast. Most of these animals probably drift to Tasmania as pelagic larvae in southward flowing currents, and may even travel further afield to New Zealand, but have difficulty surviving to maturity and spawning. Many Maugean plant and animal species also occur in New Zealand

Seasonal distribution patterns of fishes within the Bathurst Harbour estuary, southwestern Tasmania

The distribution of fishes within the Bathurst Harbour estuary was surveyed by gillnet on five occasions and by seine on three occasions, between October 1988 and July 1989. Fish distributions did not noticeably change within the estuary in response to seasonal changes in salinity. A number of fishes were, however, possibly prevented from entering the estuary during February 1989 because of low oxygen concentrations then prevailing. The assemblage of Bathurst Harbour fishes collected by gill net was unusual in being dominated by sharks and skates, with all of the common species also being distributed in water depths >50 m along the continental shelf. Thus it has many characteristics typical of a deep water assemblage. Included amongst the Bathurst Harbour fishes was a previously unknown of species of skate which may be restricted to the estuary. By far the most common of the larger fishes was the white-spotted dogfish Squalus acanthias this species comprised 86% of the total gill net catch. Despite these large catches, a tagging study in which a very high proportion (25%) of tagged dogfish were recaptured indicated that the total population in the estuary was not exceptionally large, being in the order of only 2900 animals. Tagged dogfish roamed widely through the estuary

The biogeography of shallow-water macrofauna at Heard Island

Collections of 23 macroinvertebrate taxa associated with Durvillaea antarctica holdfasts and 58 invertebrate taxa associated with artificial substrata collectors are described from shallow-water and intertidal habitats at Heard Island. The fauna sampled possessed strong biogeographic affinities with the Kerguelen Island fauna and, to a slightly lesser extent, the fauna recorded at Macquarie Island but negligible affinity with the Antarctic. Experiments involving the offshore tethering of D. antarctica holdfasts indicated that epifaunal invertebrates rapidly abandoned detached holdfasts, but that the few species surviving after one day could probably survive long periods adrift

Seasonal changes in hydrology and the distribution of plankton in the Bathurst Harbour estuary, southwestern Tasmania, 1988-89

The hydrology and abundance of planktonic organisms (>20 m size) were surveyed at various sites in the Bathurst Harbour/Port Davey estuary on five occasions between October 1988 and July 1989, and the hydrology again surveyed in February 1991. In winter, the period of peak freshwater outflow, a brackish surface layer(= 15%o) was present to a depth of ~4 m throughout the estuary. This surface layer was present to a reduced depth in other seasons, except during summer, when the halocline broke down and surface salinities of=29%o in 1989 and =25%o in 1991 prevailed. Bottom waters were close to fully marine (~33%0) throughout the year. Surface waters in Bathurst Harbour were found to be extremely depleted in nitrates «0.1 11M). Oxygen levels were also very low (~35% saturation) during the 1989 summer, which was unusually dry, but were near full saturation during the other sampling periods. The plankton community in Bathurst Harbour contained very few taxa, particularly during the winter months. The dinoflagellate Dinophysis acuminata comprised >99% of total phytoplankton numbers in October 1988 and July 1989, while the copepods Gladioferens inermis and Oithona australis and the appendicularian Oikopleura sp. numerically dominated the woplankton community. Dinoflagellates and copepods both occurred in high densities. The distribution of diatoms within the estuary was inversely related to the distribution of dinoflagellates; diatoms occurred in low densities relative to dinoflagellates in Bathurst Harbour outside the summer months, but occurred in much higher densities than dinoflagellates in the waters of Port Davey throughout the year