Tracing changing life histories of tamure (Chrysophrys auratus) in the Hauraki Gulf, New Zealand, through otolith chemistry

Tamure (Australasian snapper, Chrysophrys auratus) is the most commonly identified fish in pre-European Maori middens in northern New Zealand. Tamure 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 Maori activities in the coastal zone also caused a decline in the range of nursery habitats available to tamure populations. We compare the trace element chemistry of tamure 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.

Automated summary

This study investigates the impact of pre-European Maori activities on the nursery habitats of Tamure populations in the coastal zone. By analyzing the trace element chemistry of Tamure otoliths from different time periods and locations in the Hauraki Gulf, the study reveals temporal and spatial variations in otolith chemistry concentrations. This research demonstrates the potential for using midden data to evaluate indigenous effects on inshore fisheries, as well as the importance of establishing pre-industrial baseline information from the archaeological record for coastal ecology studies.