Spatial variation and commercial fishing of New Zealand abalone (Haliotis iris and H. australis)

The New Zealand abalone fishery produces about 1200 t annually, mostly from southern New Zealand. The fishery, based on Haliotis iris, is managed over broad management areas within which fishing intensity is spatially dispersed. The size composition of the commercial catch depends on location within a management area but is similar for divers fishing individual populations of H. iris and reflects the size composition of natural populations. For most populations, length‐frequency distributions of abalone were normally distributed: the mean shell length of H. iris was found to vary within populations over small spatial scales (100s m). The relative abundance of juvenile H. iris was low in relation to adults suggesting, at least for exposed populations, that rates of recruitment to populations of H. iris may be low. The relative abundance and mean shell length of juveniles and adults of H. australis was much less than that of H. iris. The scarcity of H. australis and the lack of separate catch quotas for the two species are factors which explain the low to zero catch of H. australis. The spatial variation in the size composition of H. iris suggests that management would be more appropriate over spatial scales which reflect local populations rather than the large spatial areas which are used to manage the New Zealand abalone fishery.