Abalone Biology and Habitat
Belonging to the family of molluscs, abalone are large marine snails or gastropods with a hard ear-shaped shell and a muscular foot which inhabit Australia’s rocky shorelines, from shallow water up to depths of 40, or sometimes 50 metres.
Abalones (Family Haliotidae) have succulent meaty bodies and are both delicate and delicious in flavour placing them in high demand on dinner tables across the globe.
Of over 100 species of abalone living in the world today, at least twenty three of these occur in Australia: however in Tasmania it is only the two largest species which form the basis of the commercial abalone fishing industry – the green lip (Haliotis Laevigata) and the black lip (Haliotis Ruber).
The shells, which can attain lengths of up to twenty centimetres, are flat, asymmetrical (ear-shaped) and spirally coiled with a low spire and a row of open holes on a curved line along one edge. As in most gastropods, water is swept into the mantle cavity by ciliary action. The holes allow for out-flowing water to pass through carrying with it respiratory, excretory and alimentary wastes without endangering the head and other sensitive organs. From time to time as the shell grows and the abalone ages a new hole is formed whilst an older one closes over. These disused holes remain evident forming a spiral pattern around the shell’s exterior.
Another distinctive feature of these unique shells is the brilliant iridescent nacreous (mother of pearl) lining which decorates the inner surface, making the entire shell both a novel ornament and a favourite for costume jewellery.
In their natural habitat abalones are browsers, moving along in a mainly uninterrupted gliding motion aided in their locomotion by the creeping sole of their muscular foot. Abalone attach themselves to rocks with this foot which has a suction force of more than 4000 times that of their own body weight. Haliotids are herbivores, feeding almost solely upon algae and small sea weeds which they grind from the rocks. Never travelling far from the place where they first settled, abalone usually prefer to dwell in places on the seabed where drift weed is conveniently carried along by a gentle current. Seaweed, bryozoa and sponge form a covering on the outer shell of the abalone, providing it with handy camouflage.
Abalones are either male or female but lacking accessory reproductive organs necessary for copulation, they are spawners. An adult female may lay up to 500,000 eggs which are released into the sea water when induced by the presence of male sperm. Fertilisation takes place in the sea and the eggs then float for one to five days as they develop into veligers with a minute shell. The veligers sink to the sea bed attaching themselves to lithothamnion, a red sea weed covering rock, and begin to grow at a rapid rate. Growth rates depend entirely on the food supply available but it can be as much as 40 millimetres per year.
Young abalone remain vulnerable to natural predators, making a tasty dish to many varieties of fish and crabs. As such they live by day concealing themselves within tiny crevices between rocks emerging only at night to feed. Yet as they grow larger and become more sexually mature (about three years of age) they may remain out in the open while still avoiding the occasional deadly foe such as octopus, crabs, fish, sharks, stingrays and of course man.
A Healthy Marine Environment
A Healthy Marine Environment
Tasmania’s abalone industry supports and promotes a ‘clean green’ environment. Appreciating the immense importance of Tasmania’s pure, natural and pristine image when marketing itself overseas especially in sensitive export markets in Asia Pacific, the abalone industry is committed to the continued health and wellbeing of the Tasmanian marine habitat.
The harvesting of abalone (hand selected by divers) is non-destructive to the environment and responsible fishing practices have created an ecologically sustainable fishery.