Aquafin CRC - Atlantic Salmon Aquaculture Subprogram: system-wide environmental issues for sustainable salmonid aquaculture
CSIRO Oceans and Atmosphere Hobart
John K. Volkman
This proposal is a major part of initial research to be undertaken by the Aquafin CRC. This project has been jointly developed by the research agencies in close consultation with industry, Government regulators and FRDC. Within the salmon component of the CRC Environment Program, local or on-site research needs are being addressed by an existing FRDC grant 2000/164 which is designed to determine the effects of fallowing on benthic fauna and biogeochemical processes. The present proposal will examine the system-wide environmental issues facing finfish aquaculture with an initial focus on the salmonid industry. This project explicitly addresses the fact that further expansion of the salmonid industry will be limited by the industry’s contribution to nutrient loads in surrounding water bodies and possible effects on phytoplankton abundance, dissolved oxygen levels and other ecological changes. The Tasmanian State Government is proposing to limit nutrient release through the imposition of feed quotas for different regions. The quotas set are necessarily best estimates and may be overly conservative because of a lack of detailed knowledge of the effects of nutrient release on ecosystem functioning. The modelling, laboratory and associated field work proposed here provides a mechanism to identify the minimum data needs for assessing environmental conditions, allows scenarios to be tested and key linkages in the ecology of the region to be identified. However, for these to function well we need to resolve uncertainties about the influence of waters from D’Entrecasteaux Channel on conditions in the Huon Estuary, the role of organic-rich sediments in the natural cycling of nutrients and consumption of oxygen in the estuary and the manner in which phytoplankton groups respond to elevated nutrient levels. The project will take advantage of the extensive set of environmental information, data and concepts generated by the FRDC-funded Huon Estuary Study - Environmental Research for Integrated Catchment Management and Aquaculture (Project No. 96/284; abbreviated to HES hereafter). There is a demonstrable need for more effective monitoring of the environmental effects of finfish aquaculture. Predictive models can be used by industry and regulators to guide choices among alternative development strategies. For effective long-term management, it is also critical that effective monitoring programs are set in place, both to allow evaluation of the performance of environmental management strategies, and to assess model performance and reliability. This project will contribute to the design of long-term monitoring programs, by identifying cost-effective indicators and sampling designs which discriminate among alternative model assumptions and predictions, taking into account spatial and temporal variability. As well, the Program will seek advice and information from overseas agencies to take advantage of emerging technologies and approaches.
1. Our overall objective is to aquire the necessary system understnding and knowldege, and apply it, in collaboration with industry and regulators, to support development of an adaptive management program which addresses system-wide impacts and production capacity for, and allows sustainable development of, salmon farms in the Huon Estuary and D'Entrecasteaux Channel.
2. Also, to develop and implement 3-D hydrodynamic and ecological models of the Huon Estuary and D'Entrecasteaux Channel, and use these to assess an predict the environmental impacts of salmon farm nutrient loads in relation to other nutrient sources (especially catchments and marine boundaries), and to assess the level of connectivity and exchange between Huon Estuary and D'Entrecasteaux Channel, and among subsystems within the D'Entrecasteaux Channel.
3. Determine the role of sediments in estuaries and nearby channel as a source of nutrient release and oxygen consumption as an input for the modes and for comparison and processes occurring in sediments under fish cages.
4. Identify and quantify the key processes that link nutrient cycles with phytoplankton abundance and composition and determine the fate of the nutrients produced in finfish cage farms in waters of the Huon Estuary and D'Entrecasteaux Channel.
A 3D primitive equation model has been developed for the Huon Estuary and D’Entrecasteaux Channel to examine the hydrodynamics of the region. Using a nesting process the region could be represented with high resolution while incorporating forcing due to wind stress, tides, low frequency sea level oscillations and pressure gradients due to temperature and salinity distributions. Major forcing consists of river flow, which may be as large as 1000 m3 s-1 from the Huon River, wind which has an annual average speed of speed of 4.3 ms-1 from the south and tide which has a range of ~1 m during the spring tide. The full year of 2002 was simulated and calibrated to data collected during 16 months in the parallel Broadscale Monitoring Program.
The overall goal of this study is to help industry and managers design and implement an effective adaptive management strategy for sustainable development of salmon aquaculture with acceptable system-wide environmental impacts. The observations and modelling conducted by the study have led to improved quantitative understanding of the spatial and temporal variation in key environmental variables, and their response to natural environmental forcing and fish farm loads. The models are sufficiently developed to assess the likely environmental consequence of alternative future aquaculture development scenarios, and the potential for interaction with other pressures such as increases in catchment nutrient loads. These models can also assist in the evaluation of alternative monitoring and assessment strategies.
salmonid aquaculture, environmental issues, adaptive management, eutrophication, hydrodynamic modelling, biogeochemical modelling, phytoplankton ecology, indicators, monitoring, nutrients, dissolved oxygen, water quality, sediments.