Secrets of great whites: What 3-year shark study revealed
A WHITE SHARK is more likely to turn up at your beach at about 11am between the months of June and November, a new study has found.
The sharks like the water temperature to be between 18 and 24 degrees and are less active when the swell height is above 2m.
Three years of studying 444 tagged white sharks along the east coast of Australia has revealed many things about the species, but much remains a mystery.
A new paper published in the Journal Marine Ecology Progress Series looked into environmental factors and their influence on immature white shark behaviour.
The paper, which was published on October 29, and its title, gives the game away: 'environmental conditions are poor predictors of immature white shark Carcharodon carchariasoccurrences on coastal beaches of eastern Australia'.
Harvesting data from 21 satellite-linked big yellow buoys moored along the coast, it detected the presence of tagged sharks in relation to month, time of day, water temperature, tidal height, swell height and moon phase. However, collectively, these predictors only explained 1.8% of the sharks' deviance.
On the other hand, the location of the receiver buoys, which capture a shark's "geographic fidelity and local conditions" explained a sizeable 17.3% of deviance.
In other words, a white shark's movement and behaviour has less to do with environmental conditions and more to do with "undetermined" location-specific habitat characteristics or biological components, such as local currents, prey availability or competition among sharks.
Although tagging was done on the North Coast of NSW, the largest number of individuals and detections were recorded between South West Rocks and Hawks Nest suggesting this region is something of a "nursery" for white sharks.
The study found that environmental factors still had a significant effect on shark occurrence.
For example, daytime was the preferable time for white sharks peaking at about 11am.
Occurrences were lower at low and high tide and peaked at full moon and between June and November.
The 444 tagged sharks ranged in length from 130−373 cm, 60% were female and 87% were juveniles.
Eight of the tagged sharks died between April 2017 and November 2019. Three of these were euthanized following capture as part of the Queensland shark control program and three died in shark nets in the Sydney area.