## 4 Discussion
### Diving Behaviour  
Vertical movement patterns were complex, showing pronounced spatial variability in depth preferences and spatio-temporal shifts in behaviour. During continental-shelf phases, sharks spent most of their time between the surface and depths of 20-50 m. This corroborates previous research, suggesting that these depths are preferred by all life stages of the species across its range [4; 6; 7; 10; 11; 21; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46]. Habitat choice is largely the result of matching abiotic preferences, e.g., temperature, with ecological factors, such as prey availability, predation risk and competition. Juvenile EA white shark occurrence and movement patterns have previously been shown to be influenced by chlorophyll-a concentration (higher probability of occurrence in areas with moderate to high surface chla_ concentration) and sea surface temperature (SST) (highest probability of occurrence at \(\sim\)20 \({}^{\circ}\)C), but not by mesoscale eddies (in contrast to mature, female white sharks in the North Atlantic, which showed a high affinity to clockwise-rotating anticyclonic eddies) [39]. The observed variability in the vertical distribution of tracked sharks within and among individuals (Figure 4 and Figure S3) and among latitudinal areas along the Australian east coast (Figure 2) is likely driven by a complex of factors comprising the physiology of immature white sharks and abiotic and biotic environmental factors. Along the northern and central Australian east coast, tracked sharks displayed a preference for water between 18-20 \({}^{\circ}\)C, similar to previous studies in these regions [23; 24; 39]. Movement to lower latitudes coincided with the beginning of summer and increasing water temperatures along the Australian east coast. Yet, a tolerance for cooler water was evident through use of water between 14-16 \({}^{\circ}\)C south of 38\({}^{\circ}\)S, and occasional forays into the deep where temperatures as low as 7.8 \({}^{\circ}\)C were encountered. An examination of high-resolution archival data revealed oscillatory dive behaviour with V-and U-shaped dives and pronounced diel changes in oscillatory movements. Repetitive oscillatory swimming is a common feature of the tracks of nearly all epipelagic top-order predators for which fine-scale depth traces have been recorded [47], including young-of-the-year, juvenile and adult white sharks e.g., [8; 43; 48]. Studies using biologging tags on tiger sharks (_Galoecordo cucvier_) and oceanic whitetip sharks (_Carcharhinus longimanus_) suggested that these dives are likely related to prey searching behaviour [49; 50; 51]. Stomach content analyses suggest that teleost fishes are the predominant prey of EA immature white sharks [52], including pelagic eastern Australian salmon (_Arripis trutta_), which mainly occur in the upper 50 m of the water column [53]. Surface waters, which show significantly higher micronekton net biomass during the night than during the day along the Australian east coast [54], may hence attract sharks searching for silhouetted teleost prey on ascent. Foraging on benthopelagic batoids and an array of demersal and reef-associated species also seems to be common [52], and likely occurs during daytime based on the depth profiles observed in our study, which are similar to those reported for other species documented to be at the bottom, including white sharks [43; 55; 56]. High frequency oscillations during the night coupled with an occupation of relatively constant depths during the day is a unique behaviour displayed by our tracked sharks. This depth pattern differs from those of juvenile and adult white sharks tracked in other regions, which demonstrated deeper vertical oscillatory movements during the day rather than during the night [8; 48; 57]. Oscillatory behaviour of young-of-the-year (YOY) and juvenile white sharks in the northwest Atlantic, for example, was restricted to depths of \(\sim\)30-50 m and lacked any clear diel patterns [44].