Tracing Changing Life Histories of Tāmure (chrysophrys Auratus) in the Hauraki Gulf, New Zealand, Through Otolith Chemistry

Tāmure (Australasian snapper, Chrysophrys auratus) is the most commonly identified fish in pre-European Māori middens in northern New Zealand. Tāmure reproduce in open water, after which their larvae migrate to nurseries in sheltered inshore environments. The range of suitable nursery habitats in the Hauraki Gulf has declined over the last century as agriculture and industry have had an impact on the quality of inshore waters. In this study, we address the question of whether pre-European Māori activities in the coastal zone also caused a decline in the range of nursery habitats available to tāmure populations. We compare the trace element chemistry of tāmure otoliths from four Hauraki Gulf assemblages using LA-ICP-MS. The first assemblage is from an archaeological site dating to the mid-fifteenth century AD; the second is from a sixteenth–seventeenth century AD site, while the other two are from modern fish catches close to archaeological sites. We examine the portion of the otolith relating to the larval and post-larval phases. Our results demonstrate both temporal and spatial variation in otolith chemistry concentrations in the immediate post-larval phases of otolith growth. This in turn suggests changes in the geochemistry of nursery zones through time and space. This provides a potential tool for evaluating indigenous effects on inshore fisheries from midden data. It also demonstrates the value of establishing pre-industrial baseline information from the archaeological record for coastal ecology studies.