LET’S take a bit of a look at one of the giants of the ocean – the white shark. It’s not an animal that most anglers encounter.
White sharks along with tiger and bull sharks are the three species most frequently causing serious bites or fatalities to water users. The number of bites on surfers in Australia is rising over time.
Male white sharks typically reach a maximum length of about four metres and females five metres, with females over six metres having been recorded. That’s a lot of shark. Some early records of even larger individuals were misidentified basking sharks or very inaccurately measured.
Initially the longevity of white sharks was underestimated but it now known that they can live for up to 70 years of age and it takes a long time for them to reach maturity. Age at maturity is substantially higher for white sharks than it is for humans – 26 and 33 years for males and females respectively.
While white sharks can be found along ocean beaches and occasionally within Moreton Bay, they also range to the deep ocean and can be found at depths of greater than one kilometre. Individual adult white sharks are highly migratory and do cross ocean basins. For example, white sharks move between South Africa and Australia. In our region, white sharks are more commonly present in the cooler months.
There are several locations that are considered aggregation sites for juvenile white sharks on the east coast. Perhaps the best-known and researched location is around the Newcastle/Port Stephens area in NSW, but an aggregation site also occurs offshore of Fraser Island (K’Gari). As white sharks grow and mature, they switch their diet from mostly fish to consuming a larger proportion of marine mammals such as seals and whales. White sharks are frequently associated with whale carcasses that they feed on. The metabolism of white sharks is low, and they can sustain themselves for up to a month, if necessary, from a single large meal.
White sharks have a remarkably broad temperature tolerance, and this is in a large part due to them being able to regulate their body temperature by retaining heat. White sharks have been found in waters just over 3 degrees Celsius to those over 24 degrees Celsius.
Although there are significant uncertainties, the Australian population of white sharks is estimated to be between 8000 and 10,000 animals. The white shark is protected in Australian waters and cannot be retained by a commercial or recreational fisher.