Integrated Marine and Coastal Regionalisation of Australia

The Integrated Marine and Coastal Regionalisation of Australia (IMCRA), formerly the Interim Marine and Coastal Regionalisation for Australia, is a biogeographic regionalisation of the oceanic waters of Australia's Exclusive Economic Zone (EEZ). As of 2008, the most recent version is IMCRA Version 4.0.^[1]^[2]

IMCRA actually defines two bioregionalisations: a benthic bioregionalisation, based on biogeography of fish together with geophysical data; and a pelagic bioregionalisation, base on oceanographic characteristics.^[2]

The benthic bioregionalisation incorporates three separate regionalisations:^[2]

A regionalisation of the EEZ into provincial bioregions, based on the biogeography of bottom dwelling fishes. In IMCRA 4.0, 41 provincial bioregions, consisting of 24 provinces and 17 transitions.
A regionalisation of the continental shelf into meso-scale regions based on biological and physical characters, and the distance from the coast. In IMCRA 4.0 there are 60 meso-scale regions.
A regionalisation of the EEZ into 14 geomorphic units, formed by grouping the 1,134 geomorphic units defined by Geoscience Australia.

The pelagic bioregionalisation divides the continental shelf into four provincial bioregions based on pelagic fish species biodiversity and richness. Offshore waters are divided into three-dimensional water masses, taking into account water properties, circulation patterns and energetics.^[2]

List of provincial bioregions

This is a list of IMCRA 4.0 provincial bioregions:^[3]

Bioregion	Information
Bass Strait Shelf Province
Cape Province
Central Eastern Shelf Province
Central Eastern Shelf Transition
Central Eastern Province
Central Eastern Transition
Central Western Shelf Province
Central Western Shelf Transition
Central Western Province
Central Western Transition
Christmas Island Province
Cocos (Keeling) Island Province
Great Australian Bight Shelf Transition
Kenn Province
Kenn Transition
Lord Howe Province
Macquarie Island Province
Norfolk Island Province
Northeast Shelf Province
Northeast Shelf Transition
Northeast Province
Northeast Transition
Northern Shelf Province
Northwest Province
Northwest Shelf Province
Northwest Shelf Transition
Northwest Transition
Southeast Shelf Transition
Southeast Transition
Southern Province
Southwest Shelf Province
Southwest Shelf Transition	This bioregion was referred to as the South Western Biotone in Integrated Marine and Coastal Regionalisation of Australia (IMCRA) Version 3.3,^[1] and as the Southwest IMCRA Transition in the National Marine Bioregionalisation of Australia. Both Southwest IMCRA Transition and Southwest Shelf Transition are used in IMCRA Version 4.0.^[2]^[3] The region extends along the continental shelf roughly from Perth to Geraldton, Western Australia, and has an area of about 27,000 square kilometres. Depth ranges from zero to nearly 300 metres, with a mean depth of 41 metres. Geomorphically the seabed is almost entirely shelf, but there is a small area of scarp at the northern limits.^[4] The province contains two meso-scale bioregions: Abrolhos Islands, consisting of the marine environment immediately sounding the Houtman Abrolhos, and Central West Coast, comprising the remaining area.^[2] Biologically, it is a highly complex transition zone, with many species from other provinces reaching a limit of their range in this bioregion. In particular, it represents a northern limit of a number of warm temperate species, and the southern limit of a number of sub-tropical and tropical species.
Southwest Transition
Spencer Gulf Shelf Province
Tasmania Province
Tasmanian Shelf Province
Timor Province
Timor Transition
West Tasmania Transition
Western Bass Strait Shelf Transition