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.