Notomithrax ursus

Hairy seaweed crab
Notomithrax ursus
Notomithrax ursus


Temperate Australasia


Carapace that is usually obscured by dense growths of algae, sponges or hydroids attached to hooked hairs and tubercles. The claws are reddish orange with light-coloured tips and two granulose ridges are present along the segment before the hand.


Max Size: 4 cm

Sea Temperature Range: 10.5-22.4°C

Depth: 0-20m

Habitat Generalization Index: N/A

Also referred to as the SGI (Species Generalisation Index), this describes the habitat niche breadth of the species. Species with values less than 15 are found in a relatively narrow range of reef habitat types (specialists), while those over 25 may be found on most hard substrates within their range (generalists). Learn more here.

Conservation and Rarity

IUCN Status: Not Evaluated

Occurrence: Infrequent (1.3% of sites)

Occurrence describes how often the species is found on surveys within its distribution. It is calculated as the % of reef sites surveyed by RLS divers across all the ecoregions in which the species has been observed

Abundance: Solitary (1 per transect)

Abundance is calculated as the average number of individuals recorded per RLS transect, where present.

Edit by: GJ Edgar. 2008. Australian Marine Life. New Holland, Sydney