To make use of a much wider variety of data on fisheries and fish stocks than was possible with an unstructured model, we introduce a juvenile-adult age-structured production exploited fishery model with a very general recruitment function. We use the age-structured model to study the interaction between fish exploitation levels and recruitment dynamics. As case studies, we use our model results and historical fish population data from Georges Bank to investigate the impact of recent harvesting levels on the sustainability of cod fishery. We show that a constant harvesting policy with the same harvesting rate of 27 would lead to the recovery and sustainability of Georges Bank cod fishery.