Stock assessment of saddletail snapper (Lutjanus malabaricus) in east coast, Queensland, Australia, with data to June 2025

Abstract

Saddletail snapper (Lutjanus malabaricus) are a key species targeted by the Reef Line Fishery, which operates along Queensland’s east coast, predominantly within the Great Barrier Reef Marine Park. The fishery is generally considered to have commenced in 1961 and extends from the northern tip of Cape York to south of Brisbane. Saddletail snapper have separate sexes, a lifespan of up to 49 years and can grow to a maximum weight of 12 kg and a total length of 101 cm, as observed in Fisheries Queensland data.
A previous assessment estimated the stock at 13–73% of unfished levels in 2021. Several key aspects of this assessment differ from the previous assessment. Firstly, membership of the project team that guides the assessment was expanded, to include fishery stakeholders (one commercial, one recreational and one Traditional Owner fisher) as well as an independent scientist and a representative from the Great Barrier Reef Marine Park Authority. Secondly, this assessment benefited from updated data through to June 2025. Thirdly, the catch reconstruction accounted for additional mortality as a result of depredation. Finally, the key outputs were constructed as an ensemble across multiple model scenarios, rather than selecting a particular preferred scenario.
All assessment inputs and outputs are referenced on a financial year basis— ‘2026’ means ‘July 2025 to June 2026’.
The assessment used an age-structured model with an annual time step, fitted to standardised catch rates, length composition data and age-at-length composition data. The model incorporated Queensland data spanning the period 1961–2025, collected from the commercial, recreational, Traditional Owner and charter sectors.
Several scenarios were run covering a range of modelling assumptions and sensitivity tests. All scenarios were optimised using Markov chain Monte Carlo (MCMC) to better explore the robustness of the models. From these exploratory scenarios a final ‘ensemble’ of twelve scenarios were chosen for inclusion in summary reporting. This ensemble indicates that the biomass ratio at the beginning of 2026 was between 19% and 42% of unfished levels with a median of 28% of unfished levels.