ENVIRONMENTAL INTERACTIONS:
The development of Tasmania’s Atlantic salmon industry led to an increasing need for research to understand how this activity interacted with our marine environment.
The first significant piece of environmental research was undertaken through a Huon estuary study: environmental research for integrated catchment management and aquaculture. Since this study, research into the environmental impacts of aquaculture has increased.
Early research developed methods to assess and monitor sediment condition, with a strong focus on local impacts immediately below farm cages and at distances ranging up to hundreds of metres from cages.
Over time, research projects focusing on interactions beyond cage areas and in related marine ecosystems have continued to increase. This includes understanding the interactions with nutrients, biological communities, water temperature, and more.
MAIN RESEARCH THEMES AND OBJECTIVES:
- Developing methods for monitoring and managing ecosystem interactions across different growing environments
- Biogeochemical modelling and decision support tools to help understand and predict ecosystem dynamics under different management scenarios
- Environmental research for integrated coastal management
- Understanding oxygen levels, biological communities, and the role of farming and other drivers/influences in Macquarie Harbour
MARINE ENVIRONMENTAL IMPACTS OF SALMON AQUACULTURE:
Researchers across IMAS and CSIRO have spent many years conducting scientific projects to inform and support the sustainable management and development of the Atlantic salmon aquaculture industry in Tasmania, and around the world.
Ensuring the long-term sustainability of marine ecosystems requires a science-based process aimed at being able to predict, evaluate and respond to changes, potential risks and threats.
Researchers explore the environmental effects of Atlantic salmon farming to help inform those making decisions about farming of Atlantic salmon, including industry and government.
The Tasmanian State Government’s environmental monitoring and management protocols for Atlantic salmon farming have been informed by a significant body of research undertaken by IMAS, CSIRO and FRDC since the inception of the industry in 1984.
Models and observational data are two common methods scientists use to analyse marine environmental impacts.
MODELLING
Models are used to describe the natural dynamics of the system, capturing inputs of water from rivers, other nutrient inputs and the movement of water driven by ocean and coastal currents. Models are then tested using historic data, where we know what happened, which gives an understanding of the error and bias (uncertainty) in the model.
We can then apply this model, together with an understanding of its relative accuracy, to future conditions and different levels of nutrient input from farming, to predict where nutrients will flow and potential impacts that might occur and to what level.
OBSERVATION
Gathering observational data involves mapping and understanding the sea floor habitats, then adding information from dive transects, animal and seaweed counts, water samples and more. Closer to farms, samples of sand and mud are also taken, the chemistry of the sediments measured, and organisms in these samples are counted and identified.
THE LOCAL-SCALE IMPACT OF WASTE
Research in the early stages of Atlantic salmon farming in Tasmania focused on local scale impacts of solid waste, like the fish feed and faeces that physically deposits and potentially accumulates on the seafloor beneath and around pens.
This work showed the relationship between farm management practices, and the level of impact and distinct stages of sea floor condition. This included the process of degradation or build-up of increased farm organic waste on the seafloor, and the stages of recovery or assimilation, both of which could be used to classify seafloor condition and manage strategies for allowing the seafloor to recover.
The research confirmed that most organic material and the impacts from farm organic waste are concentrated immediately below and within approximately 35 metres of actively-farmed salmon cages. This decreases with distance from the cage.
This research informed the development of management controls, particularly the implementation of a compliance point used in regulatory monitoring at 35 metres from the boundary of the farm.
The key features, indicators and thresholds associated with the benthic impacts were used to inform the development of environmental standards. These standards prescribe the biological and physico-chemical impacts that are considered unacceptable if observed at the compliance points in Marine Farm Licence Conditions, now called Environmental Licence Conditions.
This research validated and refined the use of visual assessment techniques for assessing sediment health, showing that the visual appearance of the physical and biological characteristics of the seafloor was directly related to the underlying condition of the seafloor.
POTENTIAL SYSTEM-WIDE ENVIRONMENTAL EFFECTS
As the industry looked to expand through the Huon River and D’Entrecasteaux Channel region, interest and concern shifted to potential system-wide environmental effects, including its contribution to nutrient loads and the possible effects on phytoplankton abundance, dissolved oxygen levels, and other potential ecological changes.
Understanding the maximum amount of nutrient input to the system before various management criteria would be exceeded was the major focus of CSIRO and IMAS research, as part of the Aquafin CRC program (2001–2008).
The program took advantage of the extensive set of environmental information, data and concepts generated by an FRDC-funded Huon Estuary Study by CSIRO and included the development of hydrodynamic and ecological models for the whole Huon/Channel region. These models were used to evaluate the effects of current and projected farming loads.
The modelling was coupled with detailed laboratory and field investigations, to understand the process of nutrient cycling in these waterways, and the links with phytoplankton and zooplankton dynamics, including algal blooms and benthic (bottom water) biogeochemistry.
The findings of the study were critical in underpinning the Tasmanian Government’s limit on nutrient release, which put a cap on the amount of fish feed that could be used for the region.
The study also developed an effective environmental monitoring program for Atlantic salmon aquaculture. The result was the Broadscale Environmental Monitoring Program (BEMP) for the region, implemented in 2009 as a regulatory requirement.
The BEMP is a system of sampling that must be conducted over the broader system where there are farming operations, to monitor for changes in water quality and the health of important seafloor habitats that might occur in response to nutrient inputs from Atlantic salmon farming.
BEMPs have now been introduced as a system-wide monitoring requirement in other growing regions (see Marine Based Finfish Farms | EPA Tasmania).
REVIEWING MONITORING AND ASSESSMENT METHODS
More recently, the expansion of the industry into new areas, and environments, together with changes in farming practices and innovations in technology, have highlighted the need to review the monitoring methods and assessment criteria for sediment health, which were developed more than 15 years ago.
This was the focus of a recently finalised FRDC project on managing ecosystem interactions across differing environments. A key element of this project included evaluating potential interactions between local reef systems and Atlantic salmon farming, and developing methods for monitoring and assessment. Read the final report and key findings.
Read more about the Aquafin CRC project subprograms:
OXYGEN LEVELS AND BIOLOGICAL COMMUNITIES – MACQUARIE HARBOUR
When Atlantic salmon farming in Macquarie Harbour expanded in the early 2010s, ongoing monitoring detected a deterioration in sediment conditions and a major decline in oxygen levels in bottom waters. This was much greater than initial modelling by external consultants had predicted.
To understand what was going on, the focus turned to understanding oxygen dynamics in the harbour and the role of salmon farming and other influences. This included industry, IMAS and CSIRO conducting real time environmental monitoring, IMAS carrying out ongoing benthic (bottom water) assessments, and CSIRO developing a water quality model.
This work played a crucial role in informing and driving management decisions on Atlantic salmon farming in Macquarie Harbour, and redefined the allowable cap for total production within the Harbour.
Since the cap was redefined, researchers have observed a recovery of benthic conditions throughout the system, with fauna seeming to migrate back into affected areas when oxygen levels increase. However, IMAS’s most recent report on environmental conditions in Macquarie Harbour show that the oxygen concentrations in midwater, which has the longest residence time, remain low.
Modelling work has also shown the intricate play of oxygen dynamics between the influences of seawater inundation from the Southern Ocean, river inputs from the Gordon and King Rivers, and the wind from prevailing weather conditions.
The research shows an intricate link between environmental conditions in Macquarie Harbour – particularly dissolved oxygen, salinity and temperature – and the ecology, movement and physiology of the Maugean skate.
IMAS research recently found that Macquarie Harbour is the last remaining habitat of the Maugean skate – a marine environment that is significantly impacted by human activity.
Although it is unclear how the population dynamics of the skate are affected by changes to the environmental conditions and other pressures in Macquarie Harbour, research published in May 2023 revealed that the Maugean Skate population has rapidly declined, with relative abundance dropping by almost half between 2014 and 2021 in Macquarie Harbour. It highlights that the environmental changes in the harbour have increased the skate’s vulnerability to sudden high-imapct events, such as water column turn-over driven by westerly winds or dramatic shifts in oxygen levels.
The urgency of managing the potential threats to this species is clear, as is the need for ongoing population monitoring to support future conservation action and ensure the survival of this unique and micro-endemic species.
Read more:
- Maugean skate research (IMAS)
- Latest update on environmental conditions in Macquarie Harbour (IMAS)
- Review of Macquarie Harbour BEMP monitoring data from 2011-2020
BROADSCALE BIOGEOCHEMICAL MODELLING AND MONITORING, HABITAT MAPPING AND DECISION SUPPORT TOOLS – STORM BAY
The Storm Bay Research Program is a suite of FRDC research projects that will provide scientific knowledge and tools to inform the management of Atlantic salmon farming within Storm Bay. The four priority research projects are:
- The IMAS-led Storm Bay Observing System project is tasked with developing and implementing an environmental monitoring program that assesses the interaction between the environment and farming operations at both local and system wide scales. This work will map and monitor a range of habitat types throughout Storm Bay, including water column, soft sediments, inshore and deep reefs and seagrass habitats. It will provide a robust understanding of these habitats to ensure the industry’s environmental footprint is well understood, and future monitoring will capture any habitat changes or impacts.
- The CSIRO Storm Bay Modelling and Information System project has built an information system that delivers water quality observations and biogeochemical model results, to inform the sustainable development and management of Atlantic salmon farming in Storm Bay. It involves developing a 3D model simulating hydrodynamics, sediment and biogeochemical dynamics, that evaluates water quality and nutrients to estimate the ecosystem’s capacity to assimilate Atlantic salmon-related nutrient inputs. The model is validated against observations from satellites, moorings, autonomous gliders, benthic landers, and in-situ monitoring programs to ensure it is sufficiently accurate. Model simulations give researchers the ability to understand current environmental conditions and forecast the environmental response under alternative management.
- The CSIRO Decision Support Tools project is delivering systems and knowledge for ongoing science-based resource management in Storm Bay. It aims to provide key stakeholders with access to practical tools and capabilities, to support decision making on environmental aspects of aquaculture operations. These tools include a visualisation system to display and deliver model results, a re-locatable downscaling model and an assessment tool to rapidly estimate the water quality impacts of changing Atlantic salmon loads.
- The Governance and Communication support project will coordinate and support project governance and communication outputs of these three projects.
To help inform any future planning for expansion of aquaculture, researchers have worked on a range of projects to assess aspects associated with expansion, including spatial planning of potential new sites. Spatial planning can be used as a framework to assess uses and values present in specific areas of the marine environment. By doing so, it can be used to determine suitability for certain activities in certain areas, while also minimising conflict with other users or values.
Spatial planning is an important tool for assisting with decisions about the allocation of marine space for activities like aquaculture. Geographic information system (GIS)-based decision support tools for resource managers play a fundamental role in collating, visualising and analysing this information.
In 2020, IMAS released a Pilot Marine Spatial Assessment Tool designed to evaluate options for assessing and balancing marine uses in the D’Entrecasteaux Channel, south and west of Bruny Island.
Researchers used spatial information to develop maps that include information on various marine uses. These indicate visually which areas may experience marine-user conflicts, and other areas that may show less potential for conflict so may be suitable for Atlantic salmon aquaculture development.
The result was a spatial assessment decision support tool which resource managers can use to identify potential marine uses that may have conflicting values with proposed Atlantic salmon aquaculture developments. The tool can be replicated in other regions and is a good starting point in the decision-making process.
The tool was recently used in the IMAS Statewide Finfish Aquaculture Spatial Planning Exercise (2021) to explore growth opportunities for salmon aquaculture in Tasmania.
The project developed and applied the decision-support tool to identify these opportunities, should they exist. Decision-support tools promote transparency in decision-making by providing an approach where the input of information (data) is meticulously detailed, assumptions are explicit, and caveats are identified.
The biophysical suitability assessment of Tasmanian waters extended to three nautical miles offshore, and included a social, economic and environmental evaluation. The report found that most opportunities for salmon aquaculture generally reside in Tasmania’s deeper offshore waters.
These decision-support tools can be used by all stakeholders, so can form solid foundations to ensure the sustainable use of marine resources.
The Tasmanian Atlantic Salmon industry has developed and expanded consistently since the 1990s. However, the options for industry expansion are constrained by the limited availability of inshore farming sites, community concerns and overlap with other activities in inshore coastal areas.
In 2016, an IMAS-led report reviewed existing and emerging options for industry expansion, and developed a decision support framework for evaluating these options. The report concluded that any farming growth on Tasmania’s coastline would need to address and ideally reduce environmental impacts if industry is to have broad community acceptance of its operations through social license (SLO) in the state’s waters.
The report also identified a need for industry to focus on alternative technologies that are more sustainable. This includes technology that enables expansion into higher-energy offshore areas and land-based closed-containment recirculating aquaculture farm systems, which are achievable but not yet established as commercially viable.
Industry growth will also require significant financial resources and involve Atlantic salmon companies finding solutions to amoebic gill disease (AGD). Expansion will also be underpinned by retention of biosecurity legislation, brand equity and reducing the cost of production.
PLANNING FOR A BLUE FUTURE
The Planning for a Blue Future global salmon conference in 2017 explored how the Tasmanian Atlantic Salmon industry could grow production safely and sustainably over the next two decades. The conference looked at growth through environmental planning, monitoring and regulation, biosecurity status, risk and planning, new technologies and innovative farming methods.
Two overarching themes emerged from plenary discussions:
- the need to restore and improve social acceptability and community engagement
- the need for more robust multiple use planning and management.
The future farming sessions explored the underlying drivers for adopting three technologies to potentially mitigate the environmental impact of nutrient enrichment:
- offshore high energy farming
- land-based/recirculating aquaculture systems (RAS)
- integrated multi-trophic aquaculture (IMTA).
THE BLUE ECONOMY CRC
The Blue Economy CRC is a major research collaboration hosted by the University of Tasmania. This CRC will directly address the research needs that will support the Atlantic Salmon Industry to expand into offshore (deeper and high-energy) waters.
It considers not only the infrastructure and logistical needs of operating offshore, but also the planning and production and how it may need to be modified for offshore conditions, especially in the context of ensuring sustainability and healthy ecosystems. For example, it is looking to new opportunities to partner with renewable energy on multi-purpose platforms.
INFORMD—AN ASSESSMENT MODEL FOR SOUTH-EAST TASMANIA
The INFORMD / INFORMD2 (Inshore Network for Observation and Regional Management: Derwent-Huon) project was a research collaboration between the CSIRO and IMAS that ran from 2008 to 2017. It involved development of a comprehensive model system for south-east Tasmania.
The aim was to achieve improved planning, management and development in marine and coastal ecosystems. It included a “Your Marine Values” element which was designed to identify what Tasmanian’s value most about the marine waters of southern Tasmania.
INFORMD / INFORMD2 observed, assessed and predicted the coastal environment and social impacts caused by changes to farming practices in the Derwent and Huon estuaries, and in the Bruny Island and D’Entrecasteaux regions.
The development of a biogeochemical model provided an opportunity to explore future outcomes under different strategies of management regarding potential system wide changes, and allowed suitable nutrient budgets for the system to be examined using all nutrient inputs including Atlantic salmon farming.
Two model tools were also developed, one to identify the ways aquaculture and marine users interact, and the other to help stakeholders assess impacts of Atlantic salmon farming on water quality. Several of the management approaches are now being applied across Australia.
