ABSTRACT
Juvenile White Sharks (JWS) in Australian waters appear to occupy different coastal habitats during their early years. Two juvenile nursery areas are known in southeastern Australia, each with different resident periods. Juveniles are seasonally resident in the Port Stephens region of central New South Wales from mid-August to early January. Sharks commonly occur at the second known nursery area in coastal waters of eastern Bass Strait, 900 km south, from January to April. Movements between the two nursery areas occur in the nonresident periods. At the Port Stephens site, sharks are highly visible in the nearshore surf zone where interactions with recreational ¢shers and beach users are frequently reported. To examine potential interactions in these coastal zones, habitat use within and between the nursery areas is being studied with a range of electronic tags. Twenty-¢ve JWS have been tagged in the Port Stephens region, seven of these with a pop-up archival transmitting (PAT) tag. Because six of the PAT tags were washed ashore and returned, the full archive data set was recovered. We used a novel mean ¢rst difference analysis, guided by supplemental location data from satellite and acoustic tags where available, to de¢ne behavioral modes and provide an indication of habitat use when sharks were resident at and when traveling between the Port Stephens and the Bass Strait nursery areas. These analyses identi¢ed a suite of behaviors for sharks ranging from shallow-water bottom-orientated swimming behavior consistent with surf-zone habitat use, diel behavior in deeper waters, continental slope (400-600 m), and openocean excursions with dives to nearly 1000 m. The transition phase between residency and traveling
periods was characterized by multiple behavior modes indicative of short forays between the surf zone and shelf edge. Classi¢cation of the behavioral modes allows estimates of time when human interactions may occur, even without ¢ne-scale position data.
