During the 3 years of the study, scallop spatfall was observed to occur over a short period (October-December) after the scallops had spawned in spring. Growth was rapid and scallops reached an acceptable harvestable size of 70mm within 16 months. Spatfall one year can therefore be related to recruitment during the next. Years of high and low spatfall were reflected in subsequent differences in recruitment. Though more years' data are required, indices of spatfall provide managers and fishermen with predictive information on likely recruitment strength one year in advance.

Each year the strength of recruitment and the residual stock size were estimated from the results of surveys by SCUBA divers. The results have shown that commercial viability of the fishery is primarily dependent upon recruitment each year. Residual stocks are normally insufficient to support the fishery in the event of poor recruitment.

Estimates of growth and mortality rates determined from tagging and data on seasonal changes in meat yield have been used to develop a mathematical model which can be used to determine number of scallops available each season and yields obtainable from different management strategies. Estimates from annual survey, of stock abundance and mean scallop size at the beginning of each year provide the data for the model.

As a result of the research program, the need to continue monitoring spatfall in Port Phillip Bay and to conduct surveys of recruitment strength each year has been identified. These data are necessary for fisheries managers to maintain the ability to manage the stocks by quota system.