Marine Life and Their Habitats

 

The wide range of rock types, tidal ranges and rainfall around Tasmania has produced an exceptionally wide variety of estuary, coastal wetland and lagoon types in a relatively small area. The combination of sheltered conditions and inputs from both marine and terrestrial sources means that wetlands, saltmarshes, intertidal seagrass meadows and other foreshore flats inside coastal inlets are also particularly rich in the variety and abundance of species of plant and animal life. These areas act as nurseries for many marine species and possess high productivity that supports flora and fauna.

A classification of Tasmanian Estuaries and Assessment of their Conservation Significance, using Ecological and Physical Attributes, Population and Land Use is available on the UTAS website.

Information about shorebirds can be found on the Department of Environment and Energy website at environment.gov.au/biodiversity/migratory/waterbirds/index.html.

Soft-bottom habitats (sand, mud and seagrass) are the dominant feature of inshore marine environments in Tasmania, particularly beaches, embayments, coastal lagoons and estuaries. While most soft-sediment habitats are not vegetated, extensive areas of seagrass occur in a number of areas around Tasmania. Vegetated sites usually possess a great deal of faunal diversity and abundance.

Differences in exposure to the prevailing weather patterns exert a strong influence on subtidal reef communities. Plants and animals living on the shallow rocky reefs in western Tasmania are adapted to exposed, harsh conditions, while species along the northern Tasmanian coast experience milder conditions, with lower swells and warmer water temperatures. Not surprisingly, biological communities associated with reefs in the two diverse regions possess many differences.

In general, the rocky reefs of Bass Strait have a high diversity of plant and animal species, and relatively low productivity. West Coast reefs support fewer species, but organisms present can occur in extremely high abundance.

Tasmania's reef communities are dominated by large seaweeds, which form large, dense forests on inshore reefs. Invertebrate animals, particularly sessile organisms such as sponges, ascidians, bryozoans, hydroids and soft corals are key features.

The most obvious change in Tasmanian reef communities has been a huge increase in the prevalence of eastern Australian species at the expense of traditional Tasmanian species.

There are around 600 named islands, rocks and reefs present around the Tasmanian coast. The majority of these are true islands, with most of the landmass lying just above the high-water mark. Many islands support flora and fauna of conservation significance, including breeding populations of seabirds and seals.

For more information you may wish to view the following publications, available via the Parks and Wildlife Service website:

 

Very little is known of Tasmania's offshore marine ecosystems as there has been only limited surveys of benthic biota.

One of the more distinctive ecosystems of Tasmania's continental shelf is the offshore seamount field located between 50 and 100 km off southern Tasmania. In this region, about 70 seamounts - the cone-shaped remnants of extinct volcanoes - arise from water depths of between 1000 and 2000 m. Seamounts create a distinctive deep-sea environment by enhancing current flow across the seabed; consequently, little sediment is deposited and unique deep-sea benthic communities can evolve, dominated by corals and filter feeders. Fishes such as the orange roughy and deepwater oreos aggregate in these areas.

Seamounts in the region contain a diverse fauna, a high proportion of which have not been recorded elsewhere. The fauna is highly vulnerable to trawling and possess a slow rate of recovery from disturbance. Recent surveys have shown that trawl operations appear to have significantly impacted the most heavily fished seamounts.

The diversity and endemism of the marine macroflora in the temperate regions of Australia, including Tasmania, are among the highest in the world with about 125 species of green algae, 225 of brown algae and 800 of red algae.

Although the Tasmanian flora remains poorly known because of a lack of professional algal workers, the south-eastern Tasmanian region includes probably the highest level of localised endemic species in Australia.

The cold temperate species of Tasmania include the largest Australian seaweeds, most notably giant kelp, bull kelp, strap kelp, common kelp and other large brown algae including crayweed.

Tasmanian waters are also characterised by the presence of several sub-Antarctic macroalgal species that are not recorded elsewhere in Australia.

Although Tasmania's extensive kelp forests are an important marine community off the State's coasts, some along the East Coast have been in decline in recent years.

Cast bull kelp, undaria and cast seaweeds and seagrasses are presently being harvested as commercial operations.

Six marine species of seagrass are recorded around Tasmania, while an additional two species occur in estuaries.

Seagrass meadows play a key ecological role in Australia's coastal ecosystems and the loss of seagrass beds is considered to be one of the most serious issues in Australia's marine environment.

Seagrass habitats in Tasmania, as elsewhere in the world, have been lost, fragmented and damaged by development and poor catchment management, through practices such as sewage and stormwater discharges, urban runoff, dredging, boating and land reclamation.

A very large number - probably well over 100,000 - species of marine invertebrates are found in Australian waters. Our knowledge of species in different habitats is however extremely patchy: the number of deep-water benthic fauna, in particular, is huge but almost unknown.

By contrast, large species of Crustacea (lobster, prawns and crabs) which provide a significant commercial resource in southern Australia are relatively well described. Notable amongst these species are the southern rock lobster and the large deep-sea crab (giant crab) Pseudocarcinus gigas, the largest crab in the world by weight.

Species of Mollusca, such as abalone, oysters and scallops, are also of direct economic importance in Tasmania and similarly their status and biology is relatively well known. In particular, major commercial fisheries have developed for blacklip abalone and to a lesser extent, greenlip abalone and also, scallops. In the cooler water of Tasmania and Victoria the Maori octopus is of commercial importance and is one of the largest octopuses in Australia (having been recorded with arm spans longer than 3 m and weighing more than 10 kg).

Other molluscs are also well represented in southern Australia and Tasmania such as sea-slugs with over 500 recorded species. Volutes and cowries represent a relic fauna in Tasmania and southern Australia, with several species being very rare. In Tasmania particular species are highly sought after by shell collectors.

Echinoderms (seastars, sea urchins, feather stars, sea cucumbers etc.) are also an important faunal element of Tasmanian and southern Australian waters. Several species are at risk from extinction.

The Tasmanian fish fauna is highly diverse and includes more than 600 species. See our Species Guide. Over 50 species are utilised commercially, with 15-20 species contributing most to the annual commercial fisheries catch.

Tasmania possesses a few fish that are found only in the far southern region, particularly the south-eastern embayments and at Port Davey in the south-west. Within the shallow waters of Port Davey, sharks, skates and rays that are common at 50 metres depth on the continental shelf replace the normal mixture of wrasses, leatherjackets and other common coastal reef fish.

Most notable amongst the south-eastern Tasmanian fishes are several species of handfish. These fish, do not have a pelagic larval stage and have extremely localised distributions. All species of handfish are protected in Tasmanian waters.

Other rare and endemic species of significance in Tasmania and southern Australia are pipefishes, seahorses and seadragons.