The habitat of the Great White Shark: oceans of opportunity
Written by Daniel Enderes.
The majestic Great White Shark glides by some very excited Adventure Bay Charters patrons!
White Shark Habitat
White Sharks (Carcharadon carcharius) frequent the offshore Islands of South Australia. Adventure Bay Charters operates out of one of the largest stretches of pristine, temperate reef in the world – a popular feeding ground for White Sharks. In this blog, we will describe the distribution and habitats of the White Shark in Australia. We would also like to introduce the Great Southern Reef and describe some of the unique habitats and environmental processes that allow the South Australian coastline to flourish – ultimately supporting keystone species such as the White Shark. However, these are pelagic animals (meaning they spend their time in the water column of the open ocean) and display complex migratory behaviour throughout their lifecycle. They are not known to live in one specific area or territory but travel large distances between sites of temporary residency (1).
Due to such challenging features, researchers still have a limited understanding of the habitats that are specific to the White Shark. We will focus on our local area, a site they are known to reside temporarily throughout the year, the Neptune Islands (Ron and Valerie Taylor) Marine Park. We are lucky to have our wild rugged backyard as the home of Great White Shark diving in Australia!
Map displaying the location of Neptune Islands relative to Port Lincoln, the area where the Great White Sharks finds the salty crew of Adventure Bay Charters hanging out most of the time… Or is this the other way around? Source: 5) National Parks SA 2018.
In Australia, the White Shark has been observed from North-Western Australia around the south coast and to central Queensland. This is fitting with the global range of the species, which is confined to temperate, subtropical habitats, with water temperatures between 12 and 24°C (1). They are found from inshore coastal habitats to outer continental shelf and continental slope areas. However, they also have the impressive ability to cross entire ocean basins during their migration!
Global habitat ranges of the Great White Shark. Source: 6) National Geographic 2013.
Research collected via tagging and tracking White Sharks suggests they move seasonally along the Western Australian coastline – as far as North-West Cape during Spring and returning to South Australian waters by early Summer (1). Along the east coast, observations of movement lead northward during the Autumn–Winter months and south in Spring–early Summer (2). They also inhabit different regions based on their lifecycle stage. For example, juveniles have been observed aggregating around key areas such as the 90 Mile Beach off eastern Victoria and the coastal region between Newcastle and Forster in NSW (3). However, research on shark migration in Australia is ongoing and there is a large gap in knowledge regarding the variability of seasonal migrations. What we do know, is that migration revolves around sites of temporary residency. Sites such as the Neptune Islands of South Australia, the Recherché Archipelago off the south coast of Western Australia, and areas of the Great Australian Bight (3) are often separated by thousands of kilometres.
Temperate habitat at the Neptune Islands
Australia’s southern coastline, where the Neptune Islands are located, is mostly composed of rocky reefs dominated by kelp forests. We know this isn’t as interesting as a colourful coral reef! However, this ecosystem is gaining more interest and recognition for being so productive and unique. It is depended upon by many endemic species (found nowhere else on Earth). Plus, by primary commercial and tourism industries.
This Great Southern Reef, as recently termed, is a global biodiversity hotspot for many interesting sea creatures including seaweeds, sponges, crustaceans, molluscs, bryozoans, echinoderms and chordates (4). While they are often overlooked for not being as exciting as the playful Sea Lions, seabirds and sharks that we keep our eyes peeled for on the water, marine plants such as kelp (Ecklonia radiata) and seagrass (Posidonia australis) have many important roles within an ecosystem. That is, they are both foundation species and ecological engineers. They provide the building blocks for ecosystems and provide many services including acting as a nursery habitat. Ultimately, they are supporting complex and productive food webs.
The foundation species of the Great Southern temperate reefs, the kelp Ecklonia radiata (left) and seagrass Posidonia australis (left). Source: 7) Majorca Daily Bulletin 2017.
South Australia has the longest south-facing coastline in the world. It features diverse marine habitats and ecosystems – with seagrass, sandy sea floors and deep-water zones. It also hosts a large range of marine life. Regions of high prey density are where you will find White Sharks. The Neptune Islands are home to breeding and feeding grounds for Australian Sea Lions and Australia’s largest colony of the long-nosed fur seals. Therefore, it is obvious why this area is an incredibly important and supportive habitat for White Sharks.
The need for protection
Ecosystem-based management is now used to protect the animals we love and the immeasurable environmental services provided to industry. This takes a more holistic approach to management and aims to protect the habitats that support animals throughout their lifecycle. Marine parks are a powerful tool at our disposal to achieve this. The Neptune Islands Marine Park’s various levels of highlights the positives of management. Within this area, we have Sanctuary Zones prohibiting the removal or harm of animals, plants and marine products providing high levels of conservation. Habitat Protection Zones allow low impact activities and use that does not harm habitats or ecosystem functions. Thankfully, this management helps to protect species, particularly of conservation concern.
Overall, further research is required to identify the habitats, migratory paths and specific locations used in essential White Shark life-cycle stages. This includes activities of mating and pupping, as well as sites of temporary residency during migration and feeding. We will be in a stronger position to conserve the Great White Shark if habitat threats can be minimised and understood. Apex predators which are currently listed as ‘vulnerable’ on the IUCN Redlist including the White Shark can only benefit.
1) Department of Sustainability, Environment, Water, Population and Communities
2012, Species group report card — sharks. Available from: http://www.environment.gov.au/system/files/pages/a73fb726-8572-4d64-9e33-1d320dd6109c/files/south-west-report-card-sharks.pdf.
2) Bruce, BD, Stevens, JD & Malcolm, H 2006, ‘Movements and swimming behaviour of white sharks (Carcharodon carcharias) in Australian waters’, Marine Biology, vol. 150, pp. 161–72.
3) Department of Environment and Energy 2018, Species Profile and Threats Database for Carcharodon carcharias — White Shark, Great White Shark. Available from: http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=64470
4) Australian Academy Science 2018, Who’s heard of the Great Southern Reef? Available from: https://theconversation.com/australias-other-reef-is-worth-more-than-10-billion-a-year-but-have-you-heard-of-it-45600
5) National Parks SA, Neptune Islands Group (Ron & Valerie Taylor) Marine Park 2018.
Available from: https://www.environment.sa.gov.au/marineparks/find-a-park/eyre-peninsula/neptune-islands.
6) National Geographic 2013, Geography in the News: The Great White Shark’s Habitats. Available from: https://blog.nationalgeographic.org/2013/02/03/geography-in-the-news-the-great-white-sharks-habitats/
7) Majorca Daily Bulletin 2017, Ecological buoys for anchoring over posidonia meadows.
Available from: https://majorcadailybulletin.com/news/local/2017/05/20/47948/ecological-buoys-for-anchoring-over-posidonia-meadows.html