The innovative tool allows scientists and aquaculture managers to test the “big picture” environmental impact of various fish farming scenarios over large tracks of water as well as the localised impacts of individual farm leases.
Developed over four years by the South Australian Research & Development Institute (SARDI) to monitor aquaculture in the Spencer Gulf, the model simulates the level of nutrients in a given area of the gulf and how the ocean circulation in that area might diffuse or disperse them. Nutrient levels impact directly and indirectly on the health of phytoplankton – the tiny plants at the base of the marine food web.
When applied to a spatial planning tool through a graphical user interface, the model allows managers and producers to rapidly assess the suitability of new and existing aquaculture finfish sites at the scale of the gulf, region or lease.
The tool is known as CarCap1.0, reflecting the importance of “carrying capacity” – the concentration of nutrients in the ocean – in determining whether aquaculture developments can proceed in Australia.
While primarily designed to help authorities manage present and future aquaculture development in Spencer Gulf (currently worth around $240 million a year at the farm gate), the system is attracting interest from industry because it can help producers improve feeding regimes and the seasonal placement of fish within their leases.
“We are currently working with one large commercial client, helping it make the best decisions based on the modeling of various options,” said the project leader and head of SARDI’s Oceanography Group, Associate Professor John Middleton.
“It is a very cost-effective solution for them because we have done the base work and can easily feed in scenarios specific to the company.”
The project attracted great interest when Assoc Prof Middleton presented to the World Aquaculture Conference in Adelaide.
“It was a big study, it was different to what has been done elsewhere and it can form the basis for future studies elsewhere both nationally and internationally,” he said.
“Although Spencer Gulf specific data collected in this project cannot be transferred to other areas, the methods and approach to better define environmental carrying capacity of a given body of water with various sources of nutrient inputs are applicable to other geographical areas, as well as to aquaculture, fisheries and marine-based commercial activities.”
The project data was collected through the Southern Australian Node of the Integrated Marine Observing System (SAIMOS), a $10 million program established five years ago by SARDI, South Australia’s Flinders University and the Australian Government to monitor the coastal boundary currents and planktonic ecosystems.
The data covers a range of factors from ocean circulation and seasonal variations in climate and rainfall, to temperature, salinity, oxygen, and phytoplankton and zooplankton levels.
“This information gives far more interconnected detail and is more useful than what we’ve had in the past,” Assoc Prof Middleton said.
Significantly, the system can differentiate nutrients created through aquaculture from those occurring naturally or from other sources such as wastewater disposal.
The good news for South Australia is the natural input of nutrients into the gulf is about 18 times greater than human-related nutrient inputs, suggesting that current aquaculture is sustainable and there is scope for expansion.
The system also has potential beyond aquaculture. South Australia’s Environment Protection Agency has already expressed interest in its ability to model salinity levels in water, for example.
The Spencer Gulf Ecosystem and Development Initiative is one of the first of its kind in the world, aiming to provide all stakeholders with access to independent and credible information about the Spencer Gulf and opportunities to develop it without compromising its environment.
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