Stock assessment of the Queensland Gulf of Carpentaria Spanish mackerel (Scomberomorus commerson) fishery

Abstract

Spanish mackerel (Scomberomorus commerson) is a pelagic species that forms genetic populations (stocks) around northern Australia. For this stock assessment, we have investigated fish harvested from eastern waters of the Gulf of Carpentaria, Queensland.

This stock assessment was set up as an age-structured model with a yearly time step and length-based selectivity. The annual data inputs included total fish harvest, standardised catch rates, length structures and conditional age at length data. The model used data from 1940 to 2018.

The assessment suggested the stock in 2018 was between 30 and 40 per cent unfished spawning biomass. The recommended biological catch was estimated at 21 t, which is below the 2018 harvest of 181 t. This initial catch estimate aims to allow the stock to rebuild to the target 60 per cent spawning biomass. Smaller harvests are estimated at first to be taken in early years, which increase through time as the fish population builds higher.