Abstract
Blackfoot pāua (Haliotis iris) is a species of considerable commercial, customary and recreational value to New Zealand. Sustainable management of H. iris stocks is a challenge for fisheries managers due to its reef scale variation in growth, recruitment, and survival. Customary mechanisms such as Mātaitai reserves and Taiāpure Local Fisheries provide the means to localise management and facilitate the use of science, local knowledge, and mātauranga Māori (traditional ecological knowledge), to inform decisions about the status and management of the fisheries. The present study aimed to use science and mātauranga as it relates to aspects of the reproductive ecology of H. iris to inform management within the East Otago Tāiapure (EOT). Three methods for accurately identifying sex in H. iris: visual identification, gonad biopsies and two methods based on mātauranga were tested. Each method was found to have its advantages with respect to simplicity, accuracy and invasiveness. Visually determining sex favoured simplicity, gonad biopsies were 100 percent accurate while mātauranga approaches were the least intrusive. Transect surveys were used to track the gonad development of H. iris within the EOT. Results indicated that individuals did not come into condition for spawning within the year surveyed supporting anecdotal evidence that H. iris in the EOT did not reproduce annually like other populations. Sex ratios also appeared to be male biased with seasonal variation in ratios apparent. A diet experiment utilising feeds of Macrocystis pyrifera and Ulva spp., two common macroalgae in the EOT, was used to consider the effect of diet on gonad development in H. iris. Results showed that though M. pyrifera contained higher percentages of the fatty acids arachidonic acid (20:4(n-6)) and eicosapentaenoic acid (20:5(n-3)), which are considered essential to reproduction, individuals fed M. pyrifera lost both gonad and general body condition. Isotope analysis revealed that very little of the M. pyrifera was being consumed, unlike the Ulva spp. The rāhui (temporary closure) on H. iris fishing on Huriawa Peninsula was also investigated. Transect surveys were repeated for sites first surveyed in 2008, both inside and outside of the rāhui area. Size frequency distributions were found to be significantly different between years and areas, with mature individuals persisting within the rāhui. Differences in densities were found to be significant at the site level. The results from this research highlight both the spatial and temporal variability inherent in H. iris populations. It furthermore provides information of use to the management of the H. iris fishery in the EOT.