The use of fish cell lines, both as a research tool and a diagnostic tool, has played a major role in the development of salmonid and cyprinid aquaculture worldwide. The commercial success of these finfish aquaculture industries is due, in part, to the development of fish cell lines which are used to monitor farmed fish populations for the presence of specific viral pathogens. Based on the results of such health surveillance programs disease-free stocks can be kept isolated from infected stock through restrictions in fish movements. The current lack of continuous tuna cell lines suitable for the isolation and growth of viral pathogens of tuna could be a serious obstacle to effective disease control in tuna hatcheries and nurseries which, in turn, could have a significant negative impact on the future development of the tuna aquaculture sector. It is noteworthy that viral infections of a tuna species (Thunnus thynnus) have been documented (1). Moreover, other viral pathogens such as marine nodaviruses (2) and birnaviruses (3) tend to be catholic in their host range and should be considered a significant risk.

Development of diagnostic tools for identification of viral pathogens in other systems has been reliant on the availability of continuous cell lines for virus cultivation. Isolation and growth of viral pathogens in susceptible cell lines provide an almost limitless supply of partially purified virus for the development of improved diagnostic procedures for these pathogens (4). In order to be able to develop similar systems to service the farmed tuna sector, there is a need for continuous tuna cell lines.

The aim of this project is to develop continuous tuna cell lines to improve our capacity to isolate and characterise tuna viruses, and to enhance our response to new pathogens that may threaten farm production. Identification of disease-free broodstock, eggs and fry is essential for the further development of the tuna aquaculture sector.

REFERENCES

1. Matsuoka S, Inouye K & Nakajima K. 1996. Cultured fish species affected by red sea bream iridoviral disease from 1991 to 1995. Fish Pathol. 31: 233-234.

2. Nishizawa T, Furuhashi M, Nagai T, Nakai T & Muroga K. 1997. Genomic classification of fish nodaviruses by molecular phylogenetic analysis of the coat protein gene. Appl. Environ. Microbiol. 63: 1633-1636.

3. Reno PW. 1999. Infectious pancreatic necrosis and associated aquatic birnaviruses. In: Fish Diseases and Disorders vol. 3 Viral, Bacterial and Fungal Infections (Woo PTK & Bruno DW, eds.) CABI Publishing, New York, NY, Pp. 1-55.

4. Crane MStJ & Bernoth, E-M. 1996. Molecular Biology and Fish Disease Diagnosis: Current Status and Future Trends. Recent Advances in Microbiology 4: 41-82.

Cage-culture of marine finfish is an increasingly important economic activity in regional Australia however, the longer-term development of the industry requires that operations be undertaken in a manner that ensures the continued health of the marine environment and recognises the conservation values society places on its marine ecological assets. In particular, there is a need to better understand the relationship between farm management practices and the environmental effects of sea-cage aquaculture. Community concerns about tuna farming have focussed on impacts to marine ecosystems where the ability to quantify impacts and optimise farm management practices is of fundamental importance in securing tenure for licence holders. Importantly, because the health of the seabed also influences the water quality in and around farms, an understanding of the relationship between farm management and souring of the benthos will provide significant outcomes in terms of optimising productivity and product quality.

Traditional approaches to the assessment of ecosystem responses to cage-culture require detailed assessment and enumeration of benthic infaunal communities that are both expensive and time consuming (see eg Cheshire et al. 1996a, b). This severely limits the extent to which the conventional methods can used for monitoring and assessment. There is a need therefore, to develop tools which allow for the rapid assessment of ecosystems responses in order to provide for the cost-effective monitoring of farming systems as well as to test the effectiveness of new management practices or technologies. The resultant lack of information about these issues presents major risks to industry including uncertainty of tenure and a lack of any capacity to relate changes in farming practices to changes in ecosystems health, productivity or product quality.

To achieve these changes we need a scientifically defensible, rapid assessment system for predicting and evaluating the environmental impacts of sea-cage aquaculture. The PCR system detailed in this proposal will provide potential savings of >50% in the cost of processing samples and improve turn around times from (typically) 3-4 months to less than 1 week. This will enable industry to investigate a wide variety of issues including the relationship between farm management practices, cage technologies and the environmental outcomes of cage farming systems.

Based on the Government ESD and Oceans Policies the pearling industry is currently facing several significant concerns. These include the need to:

- demonstrate objectively that pearling activities have minimal, if any, adverse ecological impact on the marine environment.
- identify challenges and threats to the fishery's continued variability from an ESD perspective
- demonstrate objectively that the fishery is environmentally sustainable
- obtain broad ecological information to assist the industry in identifying what environmental characteristics are key elements of successful pearl farming; and
- identify what areas of research are required to substantiate the pearling industry's claim of ongoing ESD.

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.