Stock assessment of the Australian east coast spotted mackerel (Scomberomorus munroi) fishery 2018

Abstract

Australian east coast spotted mackerel, Scomberomorus munroi, is a pelagic fish species harvested by commercial, charter and recreational fishers. It forms a single genetic stock in Queensland and New South Wales. The stock is shared with NSW although over 80 per cent of the harvest is from Queensland waters. Spotted mackerel exhibit schooling behaviours that make them susceptible to overfishing.
The Queensland commercial line and net fishery operates under a quota system for spotted mackerel (140 tonnes total allowable commercial catch). Recent commercial harvest (2013–2018) was around 64 tonnes per year. Catch shares (in 2013–14) in Queensland were around 55 per cent commercial and 45 per cent recreational.
The formal stock assessment was requested to update the status of the stock and inform fishery management agencies and stakeholders on estimates of sustainable harvest that will build and maintain the fishery in the long term.
The 2018 stock assessment combined data in an annual age-structured population model tailored for the biology, management and fishing history of spotted mackerel. The age-structured population model analysed 252 scenarios based on different combinations of input data, including harvest histories, age structures, standardised catch rates and considered both high and low estimates of natural mortality.
The assessment suggests that the spotted mackerel biomass in 2016–17 is between 40 and 60 per cent of unfished biomass (all sectors and jurisdictions).
The assessment provides estimates of the maximum sustainable yield (MSY) and recommends a total allowable catch to rebuild the stock to the Sustainable Fisheries Strategy (SFS) longer term target of 60% unfished biomass (as a proxy for MEY) by 2027.