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

Abstract

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. M94007

Variation in spawning and recruitment ofHaliotis iris(Mollusca: Gastropoda)

“…This population may have been subject to atypically low levels of recruitment. This is considered unlikely because the density of juveniles from the shallow habitat is the highest recorded for the species (McShane et al 1994). The low levels of recruitment of H. iris observed in our study is consistent with results obtained by Sainsbury (1982) which he attributed to natural recruitment failure.…”

“…The results of our study, and the general observation of a scarcity of recruits in exposed habitats (McShane 1993;McShane et al 1994) suggests that intrinsically low rates of recruitment of H. iris are further modified by post-settlement events. Although the settlement and recruitment of H. iris were similar between shallow and deep habitat, few juveniles were found in deep habitat.…”

“…The study area was chosen because the sub-tidal reef supported an abundant population of//, iris amenable to regular sampling. Although stands of macroalgae (Carpophyllum maschalocarpum, C. flexuosum, Macrocystis pyrifera, and Ecklonia radiata) were common at the study site, H. iris was associated with open reef habitat as has been observed for other populations (McShane et al 1994). The community composition of reef biota was similar with depth (McShane & Naylor unpubl.…”

“…It co-occurs with a congener//, australis but at much greater densities (McShane et al 1994). In relation to other species of abalone, particularly H. rubra in Australia, H. iris appears to have low rates of recruitment (Sainsbury 1982).…”

Predicting biological variation using a simple morphometric marker in the sedentary marine invertebrate Haliotis rubra

“…The current broad-scale (100 to 1000 km, McShane et al 1994a) management of most abalone fisheries fails to account for the finer-scale variability in their population structure, leaving fast-growing populations prone to overfishing and slower-growing populations underutilised (Strathmann et al 2002, Prince 2005. In response to this localised variability, the spatial scale of management in Australian abalone fisheries has decreased substantially over recent years.…”