While population neutrality of rock lobster culture based on puerulus collection remains a priority for the rock lobster wild fishery, this can only be assured if both survival and impact of juveniles returned after on-growing is satisfactory. Addressing the possibility of cultured fish transferring infectious diseases to the wild and thereby impacting on the fishery, requires a sound knowledge of diseases of southern rock lobsters and a database on their occurrence in different marine bioregions of Tasmania. Unfortunately, this is far from the situation. Monitoring health of wild-caught puerulus has provided preliminary data under limited circumstances (Handlinger et al., submitted). The only immature fish examined directly from the wild have been puerulus, collected from limited areas of Tasmania. The most significant problems in culture to date are nonspecific issues of poor water quality, fouling related shell disease. Specific lobster pathogens have not been identified but Vibriosis may yet prove to be very important. Limited data from other populations and other species has been collated (Evans 2000).
This is clearly inadequate and the need for baseline data is recognised as a key research area for fish health by SCFA (Subprogram B for Environmental Management, National Research and Development Plan). AQUAPLAN also recognises the need for adequate surveillance and for health studies for new aquaculture industries, and the Fish Health Management Committee in Tasmania has noted that this project represents an initiative consistent with these AQUAPLAN objectives.

Bacterial infections (currently Vibrio harveyi) are emerging as mortality episodes related to stress events which are out of abalone farmers’ control. Data for appropriate antibiotic use is unavailable. Inappropriate unregulated use in shellfish including abalone has led to antibiotic resistance and residue problems in several countries. Legal antibiotic access is limited, will worsen with proposed legislative changes, and in the longer term would require at least MUP registration.

MUP would require data on a range of parameters, including tissue levels achieved with various dose rates and how this varies with size, species, temperature and physiological state, duration of residues in tissues, acute and longer term toxicity, and efficacy against the pathogens of concern under the proposed conditions. Environmental safety data requirements would limit the choice of antibiotics to those already available for other aquatic animals, that is oxytetracycline, amoxycillin, potentiated sulphonamides (trimethoprim / sulphadiazine combination), and possibly quinolones such as oxolinic acid. Each of these has major potential limitations in either stability or bioavailability under marine conditions, efficacy against current pathogens, or acceptability for aquaculture use (quinolones). Volumes required for bath treatments, leaching from feeds, and cessation of feeding in infected abalone may all limit practicality.

To address all these parameters for MUP application in not warranted unless sufficient stability, bioavailability, and tissue levels are achieved, hence this preliminary study of the practicality of administration and in vitro and in vivo bioassay of bioactivity. The techniques developed for in vitro assessment of abalone antibacterial defenses and the in vivo infection model will also indicate the role of stress and whether alternate approaches to disease control also warrant investigation. Industry appreciates avoidance is preferable to treatment, and though stress may be unavoidable, understanding its role and being able to measure the effect may assist in developing alternate strategies.