The need to reduce reliance of aquaculture industries on fish based protein resources has long been recognized as an important issue. Notably the Fisheries Research and Development Corporation have given this issue such importance it is rated among their 9 key challenges to address in the 2000 – 2005 Research and Development Plan. Substantial work has already been undertaken to address this challenge over the past 10 years. Notably, recent developments have seen the increased adoption of some grain based alternatives being used by the aquaculture feed manufacturing industries. Lupin kernel meal use by this sector in particular is a prominent success story.

As the aquaculture feed industries begin to increase their use of alternative protein resources, such as lupin kernel meals, it becomes increasingly important to develop quality assurance (QA) assessment criteria for specific feed ingredients. The nature of these criteria will vary depending on the end use of the product. An improved understanding of the nutritional value and functional properties of the ingredients is also required to maximize the use of these ingredients by these industries and to begin the QA criteria development process.

Presently the extruded fin-fish feed sector (primarily salmonid feeds) is the largest aquaculture user of value-added grain products in Australia. However, it is apparent that further development of market confidence, through resolution of some of the nutritional value assessment and processing issues, is required for some additional aquaculture sectors (e.g. prawns) to encourage routine use of these products and work addressing these issues is planned in this proposal.

Furthermore, exploration of new product possibilities has already begun in the GRDC project with the development of a series of very promising lupin protein concentrates. However, further evaluation of the potential and constraints for the use of these new and innovative products within aquaculture feeds is needed and additional evaluation in Atlantic salmon and prawns is required.

Strategic plan
This proposal is part of the FRDC Industry Development Program, Strategy – Aquaculture Development – Production and Production Systems. The project includes a technician and a postdoctoral research fellow (Dr Philip Crosbie) as co-investigator and they will both be provided with suitable professional development opportunities through the Education Program of the Aquafin CRC. Later in the project it may be possible to adopt a PhD student with an independent scholarship or include Honours and Masters projects as they are required and become available. Thus, the project will contribute to the Human Capital Development Program, Leadership and Vocational Development. This proposal includes several key research areas outlined in the Aquatic Animal Health Subprogram Strategic R&D Plan, namely the Nature of disease and host-pathogen interactions and Training and capacity building. Relevant priorities being: to provide improved knowledge of the biology of disease agents (in this case the AGD-causing organism), and an improved knowledge of host responses to disease agents which will be partially addressed by monitoring the specific antibody response to N. pemaquidensis antigens (Nature of disease and host-pathogen interactions). Both the research and service components of this proposal will expand the technical skill base in aquatic animal health and facilitate R&D knowledge transfer (Training and capacity building). This project will underpin other projects that contribute to the Aquafin CRC Health Program Outcomes ie. reduced economic impact of disease (AGD) in finfish (Atlantic salmon) farming.

Need for this research
The continued existence of Atlantic salmon farming in Tasmania is threatened by AGD. Production is expected to increase over the next few years and this will undoubtedly lead to an increase in the incidence of AGD. The AGD control method of freshwater bathing has increased in frequency with the growth in production over the past few years and this trend is expected to continue. This will present a growing cost burden to salmon growers, it is therefore imperative that the impact of AGD on the industry be reduced so as to maintain viability for the future. Multidisciplinary teams have been assembled to achieve this outcome via a number of projects. The projects are complementary and in some cases interdependent where progress in one area is dependent on progress in another area. This is particularly the case with the service component of the current proposal and the vaccine development program, where supply of infective material and a means of controlled testing of candidate vaccines are integral to success. Vaccine development requires identification of specific antigens from the pathogen that will elicit a protective immune response in the host, hence the need for significant quantities of infective material. Similarly, success of the treatment of AGD investigation is dependent on supply of cells for initial screening of a battery of potential therapeutants in vitro before attempting field trials. The research component of the proposal, which is the development of a standard AGD challenge method that can be used in experimental tanks, is essential for the success of these projects. We need to be able to consistently induce AGD in fish to economically appraise alternative treatments and candidate vaccines before moving onto costly field trials. Inducing experimental infections is widely recognised as one of the cornerstones of vaccine development (Nordmo, 1996).

Benefits
The major benefit will be enabling progress in the vaccine development and alternative treatment projects to be made. We will have in place a model to economically appraise novel treatments, experimental vaccines and other less specific means of prophylaxis such as immunomodulation. Ultimately the project will contribute to a collective outcome of lessening the impact of AGD on salmon producers and reducing the estimated 10-20% of production costs that is currently spent controlling the disease. Other benefits include a better understanding of risk factors contributing to AGD, and the opportunity to investigate the virulence mechanisms of the organism. Overall the project will contribute to research output and service. The systematic development and subsequent use of challenge models will yield publishable material. The service aspect will be in the supply of amoebae to collaborators and provision of a means to test novel therapeutants, experimental vaccines and immunomodulatory compounds.

References
Nordmo, R., 1996. Strengths and Weaknesses of Different Challenge Methods. In: Fish Vaccinology (ed. By Gudding, R., Lillehaug, A., Midtlyng, P.J. and Brown, F.) Developments in Biological Standardisation. Basel, Karger p 303-309

Management costs (ca. 10% GVP) associated with AGD are severely limiting further expansion and sustainability of the Tasmanian Atlantic salmon industry. A holistic approach that combines alternative treatments, better management procedures, the use of a vaccine and selection of stock that are more resistant to infection would greatly reduce the impact of AGD. With the exception of selection the other areas are all active components of the Aquafin CRC Health Program. A more resistant stock along with even a partially effective treatment and vaccine would be of major benefit to the long-term sustainability of the industry.

An international consultant recommended to the industry and State Government in March 2003 that a selective breeding program should be established as soon as practical. A business plan for such a program has been developed and is under consideration by the industry. A major trait for inclusion in the program was resistance to AGD. Research in relation to understanding AGD resistance for use in selective breeding was ranked second to oral treatments in an industry survey of AGD priorities in June 2003.

Selection for resistance to external parasites in breeding programs is relatively novel and AGD is an issue specific to the Tasmanian industry, therefore unlike most other production traits in a breeding program reliance on overseas research and experience is impossible. With recent advances in molecular technologies it is now possible to investigate and understand variation to disease at the genetic level. Such knowledge on AGD will allow both improved understanding of the phenotypic variation (that will benefit other research areas) and identification of specific genetic markers that would allow faster genetic gains in resistance to be made in a selection program than would be possible via standard phenotypic selection alone.

Previous research has shown a clear impact gradient associated with cage salmon farming operations, and that presence of bacterial mats (Beggiatoa) and proliferation of opportunistic species are features commonly associated with high levels of organic enrichment (e.g. Pearson & Rosenberg, 1978). The presence of opportunists, such as Capitellid worms, being classified as representative of “unacceptable impact” (Macleod et al., 2004). This premise has been validated in SE Tasmania and underpins regulatory monitoring requirements statewide (DPIPWE, 2004).

The understanding that proliferation of opportunists represents deteriorating conditions was translated to monitoring protocols in Macquarie Harbour, but the relationship between opportunists and the level of enrichment was not explicitly tested in this region. However, video surveys suggest that in Dorvilleid worms rather than Capitellids were the species most indicative of organic enrichment effects(DPIPWE, 2004). Dorvilleids can tolerate anaerobic sediments and high levels of hydrogen sulphide (Levin et al. 2013) and are known to be indicators of the impacts of finfish aquaculture (e.g. Paxton et al. 2010).

However, Macquarie Harbour is ecologically very different to other farming areas in SE Tasmania; the sediments are inherently depauperate, largely epibiotic and spatially patchy. A recent study in Canada has highlighted the need to better understand the relationships and compliance thresholds for established enrichment indicators (i.e. Beggiatoa sp and opportunistic polychaete complexes) in systems where ecological patchiness may occur (Hamoutene et al 2014); suggesting that, where there is significant potential for small scale spatial variability, normal successional responses may not be as reliable. Consequently, the responses may not be consistent with expectations developed from southern Tasmanian regions.

In this context it is important to identify the relationship between Dorvilleids and sediment condition; determining the reliability of this species as an indicator of sediment condition, and characterising the environmental conditions associated with changes in Dorvilleid abundance.