Expansion of marine aquaculture is widely predicted to fill the protein supply-demand gap as the global population approaches nine billion. Despite the vastness of the ocean, selection of optimal aquaculture sites requires application of modern tools and expert knowledge, particularly with regard to predicting, understanding and managing environmental impacts. The Environmental Impact Assessment (EIA) process therefore plays a key role in the sustainable expansion of aquaculture, and it is often a mandatory component of proposed larger-scale aquaculture developments.
BMT Oceanica’s Principal Marine Scientist, Dr. Glenn Shiell and BMT WBM’s Technical and Innovation Manager, Dr. Michael Barry, describe a state-of-the-art EIA approach to assessing the potential impacts of sea cage operations in coastal environments. Drawing on recent work for the proposed aquaculture facility near Geraldton, Western Australia, both Shiell and Barry highlight the application of a novel recovery module, with the capability to predict seafloor recovery times during fallowing.
As the world’s population grows and wild capture fisheries decline, it is expected that aquaculture will expand rapidly to meet an expected global supply shortfall in seafood, and more generally, in protein stocks. ‘Getting to Eden’, a report by the global action network, Fishing for a Future (http://www.fishingfuture.org/about-us/), suggests the shortfall in fish protein could reach 62 million tonnes annually by 2030 if not adressed via reduction of waste, improvement in fisheries management and the expansion of aquaculture.
As reliance on aquaculture increases globally, so too does the requirement for modern tools and techniques to better predict and manage the associated environmental impacts. Indeed, as the scale and number of operations increases, so too does the complexity of the environmental impacts, and the level of scrutiny applied to them by regulators, the general public and even the aquaculture industry itself. Recent controversies in Tasmania and increasing public perceptions of the alleged link between aquaculture and visible environmental degradation have put a spotlight on these issues.
It is very clear that development of aquaculture – however important to food security – must be undertaken using the best possible tools for predicting both the instantaneous and cumulative effects of aquaculture, to provide confidence that the impacts are negligible, or if not small and entirely manageable.
Despite recent advances in the development and use of numerical tools to assist with environmental impact assessment, the industry still falls somewhat short of being able to provide ‘off the shelf’ and fully integrated models capable of reliably determining the aerial extent of benthic and water column impacts and associated recovery rates during fallowing. Having access to tools that can offer these insights is often of interest to government departments so that they can provide robust and defensible advice to key stakeholders (e.g. regulators and the general public) on environmental impacts. More practically, the application of such tools can help to minimize the risk of undue criticism, better inform public perceptions and improve confidence in the environmental approvals process, leading to better outcomes for the public and industry.
In partnership with the University of Western Australia (UWA), BMT recently developed a novel and innovative suite of modelling tools to assist the Western Australian Department of Fisheries (DoF) in its assessment of a proposed aquaculture operation in the southern Abrolhos Islands, off the west coast of Australia (the Mid-West Aquaculture Development Zone, MWADZ). BMT and UWA took existing water column and benthic biogeochemical numerical tools and built extensions to allow for the numerical simulation of: the trajectory of released particulate waste and surplus feed and their final resting points on the seafloor; their subsequent saltation (if any) and lateral benthic migration; their eventual benthic accumulation; and then finally the remineralisation of accumulated particles and the associated sediment cleansing over subsequent multiannual periods.
Some of these modelling techniques are not new, however their linkage, dynamic application over multiannual periods and use to examine detailed sedimentology during fallowing is unique. Specifically, this approach allowed, for the first time in Australia, the robust investigation of predicted water column and benthic recovery times of different proposed cage configurations, and assessment of these against legislated acceptability criteria.
Understanding these processes provided DoF with the opportunity to prepare a robust and scientifically defensible EIA for the MWADZ, to estimate the carrying capacity of the zone and provide advice on the approach to operation management; all of which provided confidence to the regulator that the proposed development could be sustainably managed, without compromising the prescribed environmental values.
BMT’s knowledge of the regulatory criteria enabled the DoF to custom build an integrated model capable of answering highly specific questions asked by the regulator. The model not only predicted the zones of impact, but also assisted regulators to understand how to manage differing production scenarios through a series of timed fallowing events.
An effective EIA is key to gaining approval for any proposed aquaculture development zones. Having an integrated team of experts who can deliver the specific requirements for the EIA and provide a practical understanding of the potential constraints faced by fish farmers has undoubtedly raised the bar and set the benchmark for a new best practice approach.