Trachurus declivis

Jack mackerel
Trachurus declivis
Trachurus declivis, Bicheno, Tasmania, Photo: Rick Stuart-Smith

Distribution

Temperate Australasia


Description

Similar body shape to yellowtail scad but a greenish grey tail, fewer scales (usually less than 76 along the lateral line), and a straight rather than slightly curved front section to the lateral line. It occurs in large schools, which remain deep on the continental shelf except when surface water temperatures fall below 17°C. Fish mature at a size of approximately 270 mm when three or four years old and have a maximum age of about 15 years. A commercial fishery taking up to 40,000 tonnes per year commenced in Tas in the late 1980s to provide feed for the aquaculture industry, but it quickly collapsed through overfishing and rising local water temperatures.


Information

Max Size: 64 cm

Sea Temperature Range: 10.3-22.5°C

Depth: 0-500m

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 (4.7% 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: Large aggregations (104 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