Australia State of the Environment Report 2001 (Theme Report)
Australian State of the Environment Committee, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06751 5
Invertebrate fauna comprises all the very diverse animal taxa other than the phylum Vertebrata - i.e. 'the other 99 per cent' (Lunney and Ponder 1999). Partly owing to the long isolation of southern Australian waters, the diversity of temperate Australian invertebrates is exceptionally high, with many endemic species, particularly in the Great Australian Bight (Edyvane 1998). Australia's tropical waters host a rich diversity of invertebrate species because of their proximity to the Indo-Pacific centre of marine biodiversity and a diversity of available habitats. Most harvested marine fish depend on invertebrates either directly or indirectly, and marine ecosystems and services would largely collapse if invertebrate communities became grossly degraded.
Very little is known about marine invertebrates, apart from the few species that are harvested commercially or recreationally. The following information on some of the invertebrate groups is taken from a draft report commissioned by Environment Australia (Ponder et al. in prep.).
The majority of stony corals are found in tropical and subtropical seas, with around 390 species from the waters surrounding the Australian mainland and another 120 from the external territories. Stony corals are listed under the Convention on International Trade in Endangered Species of Wildlife Flora and Fauna (CITES).
Over 1000 species of echinoderms (sea urchins, starfish, brittle stars, sea cucumbers) have been recorded in the shallow coastal or reef waters of Australia. Sea urchins and sea cucumbers are potentially susceptible to over-harvesting.
About 10 000 marine mollusc species have been described. There are about 25 Australian species of abalone. Shellfish such as abalone, oysters, scallops and pearl oysters, and squid and octopus are commercially harvested. Few mollusc species are threatened at present although CITES lists all members of the family Tridacnidae (giant clams).
Crustaceans are found at all depths in every marine, brackish and freshwater environment. They are ecologically important in a variety of roles, as grazers, scavengers, predators and as prey.
Krill, the 'world's most abundant crustacean', has a key role in southern waters as the staple diet of many seals, whales, fish, squid, penguins and other seabirds, making it uniquely important in the conservation of many other species (Australian Antarctic Division 2000). If krill were to disappear, all of the creatures that feed on them would disappear. It has been fished commercially for over 25 years, the peak catch being 155 000 tonnes in 1981. Currently the annual catch is 100 000 tonnes which is well within ' precautionary' harvest limits set by the Convention on the Conservation of Antarctic Living Marine Resources (CCAMLR). The harvest limit is set in recognition of the importance of krill as food for many other species in the region.
Other crustaceans (such as prawns and lobsters) are fished within the framework of managed fisheries, where harvest levels are set according to catch limits or on the extent of fishing effort that can be used in harvesting. For the majority of crustaceans there is insufficient information to determine whether or not any species are threatened.
The marine mollusc Dicathais orbita .
Source: K Benkendorff, University of Wollongong.
Sponges are ecologically important, being host to multitudes of crustaceans, molluscs, worms, echinoderms and microorganisms. They can also be of economic importance as undesirable colonisers of artificial structures, and they have a pharmaceutical potential. Over 1300 species have been recorded in Australian waters. Sponges have been adversely affected by trawling through physical damage and as a significant component of bycatch in some fisheries.
Jellyfish play a significant ecological role as pelagic predators. Fifty species have been recorded in Australian waters.
There are over 900 described and undescribed species of bryozoans in Australian waters, and Australia, together with New Zealand, has the richest bryozoan diversity in the world. They are economically important as fouling organisms, and the variety of chemical compounds they produce may be useful in the development of medicines. No species are known to be threatened.
A key issue yet to be resolved is the process to be used to unambiguously identify such species and communities.
Protection for invertebrate species can be achieved in some jurisdictions through fisheries or other regulations that prohibit the deliberate destruction or taking of animals in the intertidal or nearshore zones. Habitat and ecological processes protection can be used to conserve invertebrates given their largely unknown and not understood nature.
Listing of threatened communities under EPBC Act and reciprocal State or Territory legislation is another mechanism for protection. So far only one marine community has been listed - the reefs and seagrass flats off San Remo in Victoria - in response to a proposal to develop a large marina on the site. Another special and unique community - the stromatolites of Shark Bay in Western Australia - has been placed in a reserve.
There have been few attempts to restore damaged habitats for the benefit of invertebrates. There has been some transplantation of coral, but its success is very limited. Similarly, seagrass transplantation to restore damaged habitat and degraded invertebrate communities has had only limited success and is very costly.