As one of the most prominent species sold in northern Queensland fish shops, Spanish mackerel is iconic to seafood consumers as well as commercial, recreational, and charter fishers. However, a recent assessment of the Queensland East Coast stock raised significant concern about its sustainability, with a spawning biomass estimate below 20% of unfished levels (Tanimoto et al. 2021). Historical analyses indicate a substantial contraction of the spawning aggregations of Spanish mackerel in North Queensland, with those off Cairns being extirpated in the 1990s (Buckley et al. 2017). Previous stock assessments have also shown a trend of declining abundance over the last 20+ years (Welch et al. 2002, Campbell et al. 2012, O'Neill et al. 2018). This historical sustained decline, combined with the recent low biomass estimates, raise substantial uncertainty over the continued viability of the fishery.

This stock assessment result indicates the need to rebuild the stock in line with State and National policy objectives to reduce the number of overfished stocks. The high social and economic importance of Spanish mackerel in Queensland has led to significant public debate around uncertainty in the stock assessment, and the issue being debated in Queensland State Parliament.

As a result, key research gaps need to be addressed to increase the precision of future assessments and reaffirm stakeholder confidence in the stock assessment process. This project aims to address the following research gaps highlighted by the stock assessment: (1) determine the feasibility of using a CKMR method for estimating abundance of Spanish mackerel, (2) quantify cryptic mortality from shark depredation and post release survival, (3) improve catch and effort standardisation by better adjusting for potential hyperstability occurring at spawning aggregations and make the catch rate robust against potential management change, (4) assess the influence of key environmental variables on abundance and recruitment variability. This project will inform more accurate Spanish mackerel stock assessment, thereby increasing stakeholder confidence in line with Outcomes 4 and 5 of the FRDC R&D Plan (‘optimising benefits for the Australian community through fair resource sharing based on evidence-based management’ and ‘transparent decision-making tools that demonstrate best practice in fisheries management’). The project will also directly address the high priority research needs identified by the Queensland Spanish Mackerel Fishery Working Group.