Narrow-barred spanish mackerel (Scomberomorus commerson) are widespread in the Indo-West Pacific, can be found from the Red Sea and South Africa to Southeast Asia, north to China and Japan and south to southeast Australia, and to Fiji. It is targeted in artisanal, commercial and recreational fisheries in many parts of its range, are caught primarily with gillnets, but also caught with purse seines, and worldwide reported landings show a gradual increase from 7,186 tonnes in 1950 to 23,5985 tonnes in 2006 (FAO 2009). This species is also taken as bycatch in long-line, purse-seine and gill net gear targeting larger scombrids. Several sub-regional stock assessment in the Western Indian Ocean report this species to be heavily overexploited (McPherson 1992).

Genetic evidence indicates that there are three biological stocks of Spanish Mackerel across northern Australia; however, evidence from otolith microchemistry, parasite analysis and limited adult movement (at scales greater than 100 km) indicates that there are likely to be a number of smaller biological stocks with limited interaction (Shaklee et al. 1990).

Although each jurisdiction is likely to have multiple biological stocks within its boundaries, the difficulty in obtaining relevant biological and catch-and-effort information to assess each stock individually has meant that Spanish Mackerel has been grouped into two biological stocks (Torres Strait and east coast [Queensland]), two management units (Gulf of Carpentaria [Queensland] and Mackerel Managed Fishery [Western Australia]) and one jurisdiction (Northern Territory) (Begg et al. 2006).

The assessments that are not undertaken at the biological stock level are based on the populations that receive the highest harvest rates; their status can be assumed to be representative of the highest level of exploitation that occurs on any population within each management unit or jurisdiction (Patterson et al. 2016).

The commercial mackerel fishery extends from Geraldton to the Northern Territory (NT) border and is currently accessed by a significant proportion of the WA licensed fishing fleet, representing the main target of the present day troll fishery, comprising about 80% of the total mackerel catch.

The Western Australian coast was divided into 12 general areas based on the locations of fishing ports and mackerel fishing areas. Fishing effort throughout the Mackerel Managed Fishery (Western Australia) has been relatively stable since 2006, following reductions due to management changes. The high catch rates for the two main fishery areas, both near record levels, indicate a relatively high abundance of Spanish Mackerel in these management areas (Mackie et al. 2003).