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Rocky reefs and their associated kelp beds are some of the most common habitats found under the waters of Sydney Harbour, extending from the intertidal zone to the depths of the harbour.
A reef is any solid surface under water that provides a home to encrusting organisms.The rocky reefs of Sydney provide homes for a wealth of encrusting organisms such as sponges, hydroids, anemones, worms, bryozoans, Cunjevoi and soft and hard corals.
The hard corals on rocky reefs tend to form thin encrusting layers on the rocky substrate rather than the the spectacular, towering coral structures found on tropical reefs. On rocky reefs it is the kelp that provides most of the three dimensional structure needed to support the diversity of animals that live there. Kelp is one of the most abundant and the largest of the seaweeds. It is secured to the reef by a very strong holdfast.
A variety of fish depend on this habitat for food, shelter and spawning sites at some stage during their lives. While 'rocky reef fish' communities are not as diverse as their coral reef counterparts, individual fish species may be just as numerous as in the tropics. There are around 580 fish species recorded from Sydney Harbour while more than 1500 species have been recorded on the Great Barrier Reef.
Rocky reefs are also the home of some of Sydney's best known fish residents such as the Weedy Seadragon Phyllopteryx taeniolatus, Eastern Blue Groper Achoerodus viridis, Port Jackson Shark Heterodontus portusjacksoni, Green Moray Gymnothorax prasinus, Red Indianfish Pataecus fronto, and Red Rockcod Scorpaena cardinalis.
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