Variation in spawning and recruitment of Haliotis iris (Mollusca: Gastropoda)

Variations in the gonad index, gamete production, the density of post-settlement individuals (recruits), and the density of juveniles were measured for a population of the New Zealand abalone Haliotis iris during a 4-year study. Seasonal variation in a macroscopic gonad index was consistent with annual spawning and the appearance of recruits, but there was interannual variation in the frequency and magnitude of spawning, and the timing of recruitment. Rates of recruitment of H. iris measured by three different methods (suction, examination of substrata, and artificial collectors) were recorded as low (< 1 m(-2)) in deep (6-8 m) and shallow (1-2 m) habitats. After spawning, there was spatial variation in the density of recruits and the frequency of individuals on artificial collectors. However, densities of recruits were similar between shallow and deep habitats, although juveniles were more common in shallow habitat. In the shallow habitat, the low density of recruits measured in 1 year was reflected in a low density of juveniles censused a year later, but 1-year-olds were comparatively rare in deep habitat. Habitat-related factors may affect recruitment in H. iris and may explain why levels of recruitment are lower than for other species of abalone whose recruitment has been examined.