The seasonal and geographic distribution of three size categories of white sharks, Carcharodon carcharias (<250 cm, 250-450 cm, >450 cm), is described for South Australian waters. On the basis of 217 records, C. carcharias of all sizes were widely distributed throughout the study area but were most commonly reported in inshore waters less than 15 m deep. Sea surface temperatures at the report sites ranged from 12 to 24�C. A wide range of prey items was recorded, with teleosts predominant in sharks less than 250 cm and cetaceans in sharks greater than 320 cm. The structure of the ovary of a 520 cm white shark was similar to the structures reported for other oviphagous lamnids. Sex ratios highly favoured females, suggesting some sexual segregation. Three recaptures out of 22 sharks tagged in 1990-91 have been reported, the recapture points varying from 18 to 220 km from the release points and the times at liberty ranging from 30 to 78 days.

Basic population parameters and behaviours of great white sharks, Carcharodon carcharias, were studied during four expeditions to Spencer Gulf, South Australia. In all, 58 white sharks were observed, ranging in length from about 2.2 to 5.5 m TL (X= 3.7 m TL � 0.7 s.d.); of these sharks, 32 were subsequently tagged. Many sharks were observed repeatedly, the most frequently resighted individual being seen on 22 days over a 197-day period spanning two expeditions. Sharks in the study area were segregated by sex but not by size. Females were most abundant at 'inshore' islands, whereas males occurred mainly at 'offshore' islands. Further, there were no marked differences in abundance between summer and winter. Nine ultrasonic trackings, lasting a maximum of 27.5 h, revealed three general horizontal movement patterns: downstream circling, island patrolling, and inter-island cruising. Average rate of movement was 3.2 km h-1 (n = 145 time intervals of 15 min each). Sharks generally remained near the surface or along the bottom (about 20 m), spending relatively little time in midwater. Daytime swimming depths were significantly shallower than those at night.

No abstract

No abstract

The geographical distribution and ages of larvae of the blue grenadier, Macruronus novaezelandiae, based on ichthyoplankton surveys in southern Australian waters in 1984 and 1985, indicate that the species spawns primarily off the west coast of Tasmania in winter, and may spawn on a lunar cycle. Winter spawning off Tasmania is also suggested by adult gonad morphology: gonado-somatic indices peaked in winter, and mature and spent individuals were collected off the west coast of Tasmania. Small numbers of larval blue grenadier were also collected off north-eastern Tasmania, suggesting the occurrence of small-scale and sporadic spawning in that area. The date of first spawning differed by a month between 1984 and 1985, and was apparently related to broad-scale interannual differences in the oceanography of southern Australian waters. Use of oceanographic features to retrocast spawning dates for blue grenadier suggests that shifts in the date of first spawning of approximately one month are common in this species.