Sturgeon aquaculture in Australia: feasibility study
Understanding oxygen dynamics and the importance for benthic recovery in Macquarie Harbour
Sustainable finfish aquaculture is dependent on a benthic environment that can assimilate and process farm particulate wastes. As outlined above, in MH, bottom and mid water DO levels have reached very low levels and we have observed an associated increase in the presence of bacterial mats and a significant decline in the abundance and diversity of benthic fauna. As a consequence, multiple cage sites across the harbour are now subject to mandatory fallowing. The challenge facing farmers and regulators is understanding and predicting the length of fallowing required for benthic recovery; this has major implications for future stocking plans in the harbour. FRDC project 2014/038 and 2015/024 provide the benthic baseline over the past 2 years of farming; repeating these surveys following the observed decline in oxygen levels and fauna is needed to understand benthic recovery following fallowing. It is clear that DO levels have been, and will be, a major determinant of the benthic response over the coming months and years. Thus, it is imperative that real time observations of DO levels are coupled with the benthic observations. However, it is also extremely important to improve our understanding of the drivers of oxygen drawdown and recharge, including identifying the flushing rates of the various bays and basins in the harbour as it is not just how low the oxygen levels get, but also how long they stay low that will influence ecological outcomes. The existing CSIRO Hydrodynamic and Oxygen Transport Model can help to address these critical questions.
The future of salmon farming in Macquarie Harbour depends on its long term environmental sustainability. This project will help inform the likely effectiveness and duration of any given fallowing or remediation strategy, and as such is essential for both operational management of farming activities and the long-term management of the harbour.
Report
This report provides an update on the status of dissolved oxygen (DO) and benthic conditions in Macquarie Harbour. It follows on from the results outlined in the IMAS reports released in January, May, September 2017 and January 2018. These reports described a deterioration of benthic and water column conditions in Macquarie Harbour in spring 2016, early signs of faunal recovery observed in May 2017 and a subsequent decline in benthic conditions in spring 2017 when oxygen concentrations in middle and bottom waters returned to very low levels. Oxygen concentrations in the middle and bottom waters have since improved through the summer of 2017/18 due to recharge events that commenced in late spring 2017. This report presents the results and preliminary interpretation of a repeat survey of benthic communities in January 2018 and DO monitoring data up until the beginning of May 2018. This work is part of the research project (FRDC Project 2016-067: Understanding oxygen dynamics and the importance for benthic recovery in Macquarie Harbour to address these needs) funded by the Fisheries Research Development Corporation with the support of both industry and government (EPA and DPIPWE); the scope and funding for the project was recently extended for a further two years (until April 2020).
Project products
Sentinel sensors: revolutionising our understanding and management of the estuarine environment
Seafood CRC: Education and training exchange program with NOFIMA, a world leading aquaculture research institute
Developing targeted strategies for improving product quality through selected low value seafood supply chains
Surveys have identified a market absence and yet consumer demand for well-presented, well-priced, top quality fresh and frozen WA seafood products. The market value of WA seafood may be further enhanced by the development of high quality value-added convenience products. These products may be developed using innovative processing technologies that ensure that taste and texture quality equivalent to a fresh product are achieved. Documented attention to food safety and environmental issues should also be addressed as these have been identified in consumer surveys as of importance to the discerning purchaser. Such value-adding, resulting in an extended shelf-life, may also result in export opportunities not currently available to WA suppliers.
To modify current industry practices, and develop new processing protocols to meet these emerging markets, there is a need for species specific, whole of supply chain microbiological and biochemical research, aligned with product quality assessment. Low value seafood with generally short shelf-lives will be chosen as the target sectors to maximize the potential increase in profit by extending shelf-life or by developing new product lines.
There have been no investigations to identify specific spoilage organisms that are found on seafood along the WA coast. Virtually nothing is known about any of the microflora of WA marine species. In terms of finfish in other parts of Australia, cool water fish are generally spoiled by Shewanella putrefaciens and similar pseudomonads, but the situation in warm water species is less clear with Pseudomonas fragi having been reported. The occurrence of these on WA species is unknown, but without this knowledge it will not be possible to design appropriate preservation, storage and packaging strategies to deal with spoilage organisms.