Jackass Morwong (Nemadactylus macropterus) are distributed around the southern half of Australia (including Tasmania), from Moreton Bay in Queensland to Perth in WA, New Zealand, the St Paul and Amsterdam Islands (Indian Ocean), and off south-eastern South America and southern Africa. They occur to depths of 450 m and, in Australian waters, are most abundant between 100 and 200 m. Recent genetic studies conducted by CSIRO have shown no evidence of separate stocks in Australian waters, but New Zealand and Australian stocks are distinct. Analysis of otolith microstructure found differences between Jackass Morwong from southern Tasmania and those off NSW and Victoria, but it is unclear if such differences indicate separate stocks (AFMA 2012).

Differences among Jackass Morwong in the western and eastern zones have been suggested, and it was assumed for the purposes of this assessment that there are separate stocks of Jackass Morwong in the eastern and western zones (AFMA 2012).

The commercial harvest is predominantly by trawlers in the Commonwealth Southern and Eastern Scalefish and Shark Fishery. Commonwealth assessment is based on a full population model which shows a very significant decline in biomass since the 1980s. The biomass has recently been estimated to be about 20% of the unexploited level (Wilson et al. 2009).

Targeting of morwong in the western regions of the SESSF has increased since 2001. Discard rates are generally low (<5%), and have been between 1-3% in recent years. Fish less than 30 cm are more usually discarded due to market preferences and there is more likely to be discarding of Jackass Morwong in the southern areas off the east coast due to distance from markets (Wilson et al. 2009).

Jackass morwong are currently assessed as a western and an eastern stock in Australia, but recent research indicates that there may be no stock differentiation (AFMA 2012).