Data on fish age are essential to determine the production of fish stocks. Collection of age structure data early in the history of a fishery are particularly important to determine the natural mortality rate of a population. Data relating to the age structure of populations and growth rates can also be applied to the identification of stocks. Annual estimates of population age structure are employed to identify population responses to exploitation and environmental variability and can be used to develop more data intensive methods of population assessment (eg Virtual Population Analysis). Otoliths are the structures employed most often to estimate age of fishes and validation research at the ANU indicates that toothfish otoliths are suitable for this purpose.

A "stock" is the basic unit of management in most fisheries and identification of these units is a prerequisite to accurate assessment and effective management. There are no data on stock structure for Patagonian toothfish. As a result, we have no knowledge regarding the potential impacts of toothfish exploitation outside the AFZ on toothfish stocks within the AFZ.

Knowledge of toothfish biology is extremely limited. Given the lack of baseline biological data, it would be difficult to identify possible responses of toothfish stocks to exploitation or differences in life history characteristics among putative stocks. Identification of changes in basic life history characteristics such as age or size at maturity and timing of ontogenetic migrations are important to management of fish species within both a stock and ecosystem context.