Stock assessment of the Australian east coast sea mullet (Mugil cephalus) fishery 2018

Abstract

The sea mullet (Mugil cephalus) is found in tropical and subtropical waters around the world. On the east coast of Australia, sea mullet are harvested from a single continous stock which occurs from Baffle Creek in Queensland to Eden in New South Wales. Sea mullet undertake annual migrations along ocean beaches to spawn that make them susceptible to overfishing.
This stock assessment covers the Australian east coast and incorporates Queensland and NSW catch data up to 2016. The vast majority of the harvest is taken in the commercial fishery, with the catch in NSW exceeding the Queensland catch (approximately 65% and 35% of the catch respectively).
The current assessment combined data in an annual age-structured population model tailored for the biology, management and fishing history of sea mullet and estimates the sea mullet biomass in 2016 is around 50 per cent of unfished exploitable biomass (all sectors and jurisdictions).
Biological information for sea mullet has revealed a cyclic pattern of new fish recruitment over years. This has produced a cyclic fluctuation in the exploitable biomass results with a midpoint at around 50% of virgin levels which is trending downward. The final year of the model occurs during a downward phase in a long term cycle of biomass peaks and troughs and fishing could exacerbate this downward biomass trend.
The assessment noted that the Bundaberg to Noosa stock range was experiencing below average harvests. Further assessment of the extent of regional decline will increase our understanding of the relationshop between historical levels of fishing and environmental change.
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.