D’Entrecasteaux Channel

D'Entrecasteux Channel from Gordon

D'Entrecasteaux Channel from Gordon

The D’Entrecasteaux Channel and lower Huon Estuary are partially enclosed bodies of water providing transitional areas between land and sea, and protection from the full force of ocean waves, winds and storms via promontories, islands, reefs and sandy spits.

The highly indented coastline of the region combined with diverse geology has produced a myriad of habitats for marine and coastal organisms. These include beaches and dunes, rocky foreshores, saltmarshes and other wetlands, mud and sand flats, seagrass meadows, kelp forests and rocky reefs. Some of the estuarine and marine communities occurring in these areas are amongst the most productive types on earth, such as seagrasses and kelp beds, which may produce more organic matter per area than equivalent areas of forest and grassland. Fringing wetlands also provide valuable services, such as filtering sediments and pollutants from catchment runoff, and protecting the coast from erosion.

Many of the plants and animals are specially adapted for life at the margin of the sea, while fully marine species also find refuge amongst the sheltered habitats. Large numbers of birds, mammals, fish and invertebrates depend on the habitats of the D’Entrecasteaux Channel and lower Huon Estuary as places to live, feed and reproduce. Coastal vegetation provides key habitats for terrestrial fauna as well as marine species that breed on land, and includes threatened native communities that are of high conservation value in Tasmania.

The Channel and Huon Estuary are drowned river valleys, which became inundated during the last post-glacial rise in sea level. Foreshore geology is dominated by dolerite and sedimentary rocks (sandstones and siltstones), with area of loose non-compacted sediments such as sand, silt and clay and occasional areas of basalt (between Kettering and Gordon and western shore of North WestBay). Dolerite and sedimentary reefs generally extend little more than 20‐50 metres offshore at a 5 metre depth.

Unvegetated silty sand, hard sand, and other sands are the dominant substrate types and together comprise 80% of the seabed. The remaining areas consist primarily of silt, with smaller areas of reef and seagrass fringing the coast.

Many threatened species are recorded in the area; 23 threatened fauna species and 45 threatened flora species. Threatened fauna resident species in marine and estuarine habitats include the Spotted handfish (Endangered), Live-bearing seastar, Gunn’s screw shell and Fairy tern (all Vulnerable). Seasonal visitors include the Humpback and Southern right whales (Endangered), while the Southern elephant seal (Endangered) and Great white shark (Vulnerable) are recorded occasionally, and the Australian grayling (Vulnerable) resides in freshwater habitats but includes a juvenile marine/estuarine phase.

Approximately 150 native fish species have been documented in the D’Entrecasteaux Channel and lower Huon Estuary, and adjacent coastal streams. Some species perform seasonal migratory ‘runs’ between marine, estuarine and freshwater environments, such as the threatened Australian grayling and also Brown trout, Galaxias species, Black bream, Yellow eyed mullet, Tasmanian whitebait, Shortfinned eel and Shortheaded lamprey. Common reef fish include the Blue throated wrasse, Bastard trumpeter, Senator wrasse, Toothbrush leatherjacket, Barber perch, Blotch‐tail hulafish, Common bullseye and Blue warehou. Seagrass beds are an important habitat for many fish, particularly small resident species such as the Bridled leatherjacket and Pipefishes. Dominant fish species in unvegetated are likely to include Flounders, Leatherjackets, Atherinids, Mullets and Eastern Australian salmon. In deep (>10 m) unvegetated habitats Leatherjackets, Gurnards, Skates and Stingarees are likely to be dominant species.

A wide variety of birds depend upon the diverse environments of the area, including waders, waterfowl, seabirds, woodland/forest birds and raptors. 127 species of native birds have been recorded in the study area and adjacent environs, with eight introduced species. The region is particularly important for the Pied oystercatcher Haemotopus longirostris and the Hooded plover Thinornis rubricollis.”

(Source: Parsons, K. E. (2012). State of the D’Entrecasteaux Channel and the lower Huon Estuary 2012.)

Saltmarsh Simpsons Bay South Bruny

 Lutregala Saltmarsh, Simpsons Bay, South Bruny

© 2011 Kingborough Council
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