Modelling environmental changes and effects on wild-caught species in Queensland
A better understanding of the impacts of environmental drivers on the population dynamics and abundance of key fishery species can inform flexible management decisions that pre-empt both risks of overfishing under adverse environmental conditions and opportunities for increased harvest under favourable conditions. This is increasingly important as shifting environmental dynamics drive geographical shifts in fish stocks.
This project will identify environmental variables influencing the abundance of three priority fishery species, quantify those relationships to enhance their stock assessment models, and develop a forward projection tool to inform adaptive management of each fishery. Target species - Spanner Crabs, Snapper and Pearl Perch – were selected based on key interest to management of fisheries in Queensland and NSW. Some associations between these species and certain abiotic environmental factors are already known, but there is yet to be a rigorous and comprehensive approach to this work, with the explicit goal of incorporating abiotic influences into Queensland and NSW stock assessments.
The project has three key objectives: (1) Find indices of association between measures of abundance and key environmental drivers; (2) Use these indices to enhance the existing stock assessment model for each species; and (3) Enable forecasting of environmentally driven fluctuations in targeted species’ abundance, including enhancing Management Strategy Evaluations (MSEs).
In particular, environmental correlates will be valuable to fisheries managers by: (a) reducing the uncertainty in biomass estimates, (b) explaining fluctuations in abundance, and (c) characterising what is a “bad year” for each species. Such information can be incorporated into MSEs.
The “Queensland Sustainable Fisheries Strategy 2017-2027” identifies several challenges to fulfilling its mission of ensuring the sustainability of fisheries and the economic viability of fishing sectors. The first of these is “gaps in monitoring and research, which limit the ability to make timely, evidence-based decisions”. This project will close some of these gaps and assist in formulating measures for promoting stock recovery and adaptive management.
Final report
This project studied environmental factors which may be influencing the recruitment, catchability or productivity of Snapper, Pearl Perch, and Spanner Crab stocks in Queensland. Two environmental variables: GSLA and Chl-a were found to have strong associations with either abundance or catchability across the three target species. These associations occurred at spatio-temporal scales relevant to each species’ biology. A third variable, SST, also had strong associations with Snapper.
Importantly, all three of these environment variables, GSLA, SST and Chl-a were found to have certain consistent long-term trends, with rates of change depending somewhat on the region under consideration. We demonstrated that incorporating these environmental variables into simple surplus production stock assessment models results, under some scenarios, in delays in stock recovery. This assumed that the above trends of GSLA, SST and Chl-a are sustained and the direction and strength of the identified associations are maintained.
