If abalone can be accurately aged, this would be a fundamental tool for more effective management of abalone fisheries.  Several authors have proposed ageing abalone by grinding or cutting abalone shells, and counting the shell layers deposited beneath the spire.  Other authors have cast doubt on this method.  What is uncertain is how reliable these age estimates are.  To construct useful models to assess and manage abalone stocks, it is important to know the accuracy of the data on which the model is based.  Furthermore, it is labour intensive to collect age data, and if these data are very inaccurate, then resources are wasted in collecting it.

This project aimed to find out how reliable and accurate the ageing method was, by investigating the timing and the periodicity of layer formation in abalone shells. It seemed possible that the ageing method might work reasonably in some areas, but not in others.  Thus we planned to repeat the work at many places in the hope that we could predict where ageing would be useful for managing the blacklip and greenlip abalone fisheries of Victoria, Tasmania, New South Wales and South Australia.

The Norfolk Island domestic fishery survey was undertaken by Department of Primary Industry (DPI), Canberra on behalf of the Norfolk Island Legislative Assembly. Research undertaken on Norfolk Island during 1981 to 1983 was funded by the Fishing Industry Research Trust Account (FIRTA 81/49) with contributions from DPI for computing and research design, and the Norfolk Island Government for subsidized accommodation, transport and laboratory facilities.

The program followed consultation between the Norfolk Island Fishing Club, the Norfolk Island Legislative Assembly, the Department of Territories and DPI, Canberra in response to complaints from local fisherman that fish stocks were declining. Local fishermen considered that foreign fishing vessels (FFV's) in Norfolk Island waters had depleted continental shelf demersal fish stocks.

Information is presented here indicating that the decline in fish abundance in Norfolk Island waters is a normal response to increased fishing pressure from the growing domestic fishery. Furthermore, it is believed that the Norfolk Island continental shelf demersal fishery is approaching full exploitation.

The program was designed to provide a baseline for future fisheries management.