Dugongs (Dugong dugon) were studied in 2 bays in north Queensland from shore and small boats. Population in favoured areas of one bay was 5/km shoreline and 4 to 8% were juveniles. Feeding was the most common activity. The dugongs dived and grazed, apparently using their rostral disc to gouge a serpentine track through the bottom sediment. Removal of sea grass was calculated to be 78% from the tracks selected by observers or 59% from a random sample; both were thought to be underestimated. Dugongs tended to move on after 5 or 6 days when 30% of an area had been grazed. They left inshore sea grass beds before low tide to avoid being stranded, so their feeding was governed by the 25-h cycle of 2 high and 2 low tides daily. Inshore feeding was not restricted to hours of darkness. The most commonly eaten sea grasses were Zostera capricorni, Halophila decipiens and H. ovalis. From published work, it was thought that the dugongs specialized in whatever seagrass species were most readily available. Owing to opacity of the water, they could not be observed under water. Mean length of the 9 faecal pellets found on shore was 8.98 mm; the pellets included plant fibre.

Observational techniques were tested and observations made along the eastern shore of Dirk Hartog I. in June and July of 1979. Dugongs could be closely approached by boats and divers in water with 3-5 m subsurface visibility. Dugongs detected objects in the water from much greater distances and approached and investigated boats and divers visually. This behaviour was highly stereotyped, and because other behaviours did not occur in proximity to boats or divers the effectiveness of surface and subsurface behavioural observation, photography, and attempts to catalogue individuals on the basis of distinguishing scars and other features was limited. Observation from shoreside cliffs was more productive. Vocalizations attributable to dugongs were not detected by hydrophones. Dugongs may vocalize only under exceptional circumstances. When feeding on the seagrass Amphibolis antarctica dugongs strip leaves from stalks, but do not dig into the substrate. Calves may ride on the backs of attending cows. Calves suckle beneath the surface, lying beside the cow and behind her axilla. Dugongs and dolphins interact, and harassment of a dugong cow and calf by a dolphin terminated when other dugongs interposed. Dugongs avoided a boat approaching at moderate speed, but did not take evasive action when the same boat approached at high speed.

Five aerial survey transects in eastern Shark Bay, along which dugongs (Dugong dugon) had been reported in deep water in July 1989, were flown on 3 and 14 July 1992. As in 1989, dugong sightings were concentrated between 9- and 15-m depth contours. Thermal patterns shown on images obtained from NOAA satellites, and direct measurement of temperatures in the water column, confirmed that temperatures were at least 19�C where dugongs were concentrated. Although no seagrass had previously been reported in this zone, examination of benthic communities using a remotely controlled underwater video system revealed an apparently monospecific stand of Halophila spinulosa. Dugong behaviour, observed from a 10-m catamaran, indicated that the animals were diving to the bottom. Long, deep dives may be more costly in time and energy than the shorter dives characteristic of feeding in shallow water. H. spinulosa has large fleshy rhizomes similar to those known to contain abundant starch in other members of the genus and it is suggested that carbohydrate-rich rhizomes might compensate for the higher costs of foraging in deep water. Previously known stands of preferred forage species appeared inadequate to support the large dugong population of Shark Bay, but if temperatures are favourable throughout the winter and if the H. spinulosu observed in this study is available throughout the year, this H. spinulosa community may be an important resource for the Shark Bay dugong population.

During January and February 1983, replicate box-core samples were taken at 18 stations on the continental shelf and upper slope (23-938 m depth) off the west coast of the South Island, New Zealand, to estimate biomass, faunal density, and faunal composition of the soft-bottom macrofauna. Biomass ranged from 4.3 to 422.9 g wet wt irr 2 , and faunal density from 230 to 23 190 individuals irr 2 . Biomass and faunal density were inversely correlated with depth. Polychaetes, bivalves, peracarid Crustacea, and ophiuroids were usually the most abundant taxa. Some quantitative macrobenthic data were also collected at three other South Island locations: Tasman Bay, Pegasus Bay, and off the Otago Peninsula. Results of the study in part support an earlier observation that benthic biomass off the east coast of New Zealand tends to be greater than that off the west coast. This may reflect corresponding differences in primary productivity and seasonal variation of planktonic biomass.

In midwinter dugongs concentrate in western Shark Bay, adjacent to Dirk Hartog I., although scattered individuals or groups remain in other regions. Up to 496 dugongs were counted in intensively surveyed western areas in July 1979. At least 553 individuals are calculated to have been present in the region, and a minimum population of over 900 individuals estimated for the Bay as a whole. The population seems to be a well defined isolate, and is relatively undisturbed. Conditions are very favourable for more detailed study. A method for estimating the number of animals overlooked in the blind zone directly beneath the aircraft is described. Aerial counts of dugongs varied greatly with conditions. Cloud cover had a large depressing effect: surface turbulence and subsurface turbidity were less significant. Dugong activity is concentrated on the sublittoral platform. Sites of major aggregation may not be the same in successive years. Locally favoured habitats are at the seaward margins of the sublittoral platform, and on offshore shoals. Vegetation patterns at favoured sites may reflect dugong grazing. Persistent use of favoured localities, and local shifts in concentration were observed. Distribution of other large vertebrates, and of boats, relative to that of dugongs was examined and a significant correlation between sightings of large sharks and larger aggregations of dugongs was found. Analysis of dispersion revealed that most dugongs were in groups although most sightings were of single individuals. Cows with calves were less likely to be in the company of other dugongs than were adults without calves. From ll to 12% of individuals were calves.