The workshop review concluded that (1) there are significant gaps and limitations in the existing information on the status of the abalone populations across reefs in western Victoria (West and Central zones) and exposure of these populations to the virus and (2) that the current regional model was inadequate to represent the current situation in the western zone or to evaluate management options.
In relation to the information needs, it was concluded that there was an urgent need for a repeat of the scientific surveys at all the standard monitoring sites in the western zone, and far enough into the central zone to be ahead of the virus outbreaks, during July-August 2007. The standard sampling should be augmented by genetic sampling and broad survey of aggregations on the reefs.
The current quantitative regional model is not adequate to represent the current situation in the western zone or to evaluate management options. This is because the current situation in the western zone provides both a form of depletion that is very different from fishing, in terms of the size classes affected and extent of depletion. Reefs are affected differently and the management options are also likely to vary by reef, but the existing regional model does not represent reefs. Because the current situation is unique, there is no longer a basis for assuming that the previously-used industry-based semi-quantitative assessment of reef codes will continue to be reliable.
Thus there is a need to develop and apply a quantitative model that is spatially resolved to at least the reef-code level, and to use this for assessment of population status and examination of management options at the reef-code level.
Management of the valuable Australian abalone fishery is difficult because catch/effort information for abalone does not provide warnings of declining stocks. In fact abalone fisheries in Alaska, California and Mexico have collapsed or declined dramatically, with little warning. Management must rely on a detailed knowledge of how fast abalone grow, when they become adult, how many eggs they produce, and how fast they die of natural causes. But these statistics vary between areas, and it would be very costly to measure them at enough sites for efficient management. Management of finfish stocks has been revolutionised by accurate methods to age fish, using layers in the ear bones. Ageing abalone was identified as a high priority as long ago as 1986 in an abalone research review for the then FIRDC. An ageing method would allow biologists to work out growth, natural death rates etc. rapidly and at low cost. The industry would benefit from increased security, as uncertainty about the state of the stocks is a major problem for stakeholders. A reliable method would be used by state organisations to assess stocks more effectively, thus reducing the risk of a collapse or severe fluctuations in quota.
Previous work showed layers in the spire of the shell might be useful to age both blacklip and greenlip abalone, but the evidence relates only to juveniles , and in some areas layers did not correspond to age. We proposed to show when and how age could be estimated from layers, by "timestamping " tagged abalone at sites in each state. "Timestamping" involves staining the shell layer that they deposit over a few days. When the abalone were recovered, the number of layers deposited after the timestamp stain would show how regularly layers are deposited. We set out to mark abalone shells with fluorochrome stains , used by dentists to look at the growth of teeth, and to timestamp rings in fish ear bones. Work in New Zealand had also shown that abalone could be marked with a fluorochrome.
The project began in December 1992. By June 1993 we had established that abalone were stressed and often died after injecting stains, but they were unaffected when immersion in seawater dosed with the stains, and we had tested and compared five stains in the laboratory, and identified concentrations and immersion times that produced strong marks. This achieved our first milestone. Milestone 2 was the demonstration of the "timestamping" method in the field. By the end of 1993 we had developed underwater staining tanks, and collected, tagged and stained abalone with two fluorochrome stains underwater. Our results were reported at abalone divers meetings , and the international abalone conference in Hobart in February 1994. The symposium paper is now published.
