National Heritage List inscription date 24 February 2023
The sheltered waters of South Australia's Upper Spencer Gulf Marine Park are home to the Cuttlefish Coast Sanctuary Zone.
The sanctuary is of outstanding significance to Australia as the largest known breeding habitat of the Giant Australian Cuttlefish (Sepia apama).
The sanctuary's shallow, fringing, rocky reef system lures thousands of cuttlefish to breed each year. Occurring between May and August, it is the largest and most significant breeding aggregation for the species.
Fierce competition between male cuttlefish has led to complex breeding behaviours. Spectacular displays that include changes in colour, shape and texture aim to attract or ambush potential mates.
The Cuttlefish Coast Sanctuary Zone is 63 kilometres south of Port Augusta and 15km northeast of Whyalla. Popular with recreational divers, many people visit to see the colourful displays of the species during the breeding season. Whales, dolphins and migratory birds also pass through the sanctuary.
Gallery
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Biology and ecology of the Giant Australian Cuttlefish
Giant Australian Cuttlefish are the largest cuttlefish in the world. They belong to the cephalopod class of animals. They range in size from 50 to 100 cm and 5 to 10.5 kg in weight and live for 1 to 2 years. Population numbers have fluctuated from a low of 13,492 in 2013 to a peak of 247,146 in 2020.
Giant Australian Cuttlefish are carnivorous and feed on molluscs, crustaceans, smaller cephalopods and fish. They display flamboyant and remarkable behaviours. They rapidly change colour and patterns from a white grey to iridescent black, brown, blue, orange, red or yellow. Their skin produces polarising reflective patterns, which they may use to communicate. It also enables them to change shape and skin texture to imitate rock, sand or seaweed.
The sex ratio at the site averages 4 males to 1 female, resulting in intense male to male competition for females during the breeding season. In the presence of large males, small males mimic the posture of egg-laying females, who are not receptive to mating. This allows them to act as 'sneaker' males to gain better breeding access to receptive females. This behaviour is not observed elsewhere in the world and is the first known example of an animal directly gaining a direct breeding advantage using mimicry.
Unique habitat
The subtidal rocky reef at the Cuttlefish Coast provides fragmented slabs of bedrock which forms a protective shelter for the cuttlefish and their eggs. The cuttlefish attach their eggs on the underside of these rocks or in caves or crevices. The other factors of the Cuttlefish Coast that may attract high densities of spawning cuttlefish here are:
- the west to east aspect of the reef
- high current flow
- low water temperatures (around 120C - required for incubation of eggs).
Research potential
The annual cuttlefish gathering at this site has been the focus of long-term research. It has the potential to produce new information and a broader understanding of cuttlefish and cephalopod behaviour, ecology and physiology.
Internationally, the biochemistry behind the species’ ability to change colour is being studied for use in the development of fabrics, cosmetics and other materials.