Abstract
Marine species are facing an increasing number of stressors and some species once thought to be resilient to change are now threatened. It is important to understand how species populations have changed through time so that management can be adjusted accordingly, and so that achievable restoration goals can be set. However, many species lack population data at multidecadal or longer time scales. Using historical data from the 1970s, this study investigates how the dynamics of a New Zealand abalone (Haliotis iris), or pāua, population at Peraki Bay changed over a 45-year period. No commercial fishing of the population occurred prior to the initial survey and limited commercial catch has been reported between surveys. Repeat monitoring of the H. iris population at a 45-year interval indicates that a large change in population size and structure had occurred. Since 1976, there has been an 84% decrease in estimated population size. The remaining population is restricted to where juveniles were found in the original survey. These findings are consistent with conclusions, made from modelling in the 1970s, that the population seen in the 1970s was not stable and that a possible cause was temporal variability in population recruitment.