The biology of an unfished population of the paua,Haliotis irisMartyn, in Peraki Bay, Banks Peninsula, was studied from 1973 to 1976. In February 1976 the population consisted of about 179 000 animals on 4.5 km of coastline. The length/frequency distribution was strongly skewed to the left, indicating an accumulation of old individuals and a recent history of low recruitment. Growth of animals <70 mm long was determined from changes in length frequency, and of larger animals by the analysis of tag returns. The mean parameters of the von Bertalanffy growth equation for the study population areK= 0.163 and L = 131.9 mm. Both are lower than those reported for paua in a more typical habitat near Kaikoura. The annual instantaneous natural mortality rate, as estimated by several methods from population size structure and individual growth rate data, is about 0.1. Spawning was monitored during the breeding seasons of 4 years. Spawning on Banks Peninsula failed to occur during 2 years, and the failure during 1 year was geographically widespread. No explanation for these spawning failures can be offered. The length at first maturity was the same at Peraki Bay and Kaikoura, despite a much lower growth rate and fecundity at Peraki Bay. Recruitment was 2000–5000 2‐year‐olds per year and either recruitment is largely independent of local spawning success or significant spawning occurs outside the currently accepted breeding season.