Assessing a multilevel tier system: The role and implications of data quality and availability

Tier systems for fisheries assessment and management are widely used, but defined differently by jurisdiction. A principal component analysis was applied to the expanded Australian Commonwealth 8-tier system for fishery assessment and management to determine whether it adequately delineates across stocks according to data availability and quality. The original Australian tiers comprised four levels that were defined primarily according to the available stock assessment options, given the data availability and quality. We asked fishery experts to score information quality for each of the main Australian Commonwealth species and/or fisheries. Multivariate analysis indicated that the eight tiers delineated between the extreme tier levels on the first principal component, although there was overlap for intermediate tiers. More generally, it is important that the aim of tier systems and the basis for tier delineations are explicitly defined given the increasing association of tiers with trade-offs between overfishing risk, management cost and catch.