Reconstructing pre-European marine habitats using archaeological assemblages: A case-study from the Ōtata midden, New Zealand

• The Ōtata midden is a stratified site from Ōtata Island in the Hauraki Gulf just north of Auckland, New Zealand. • Dates span most of the pre-European occupation of New Zealand (cal 1350–1800 CE). • We laser ablated snapper (Chrysophrys auratus) otoliths from three midden layers. • Juvenile snapper behaviours did not change during this period, but the environments they were swimming in did. The Ōtata midden, site R10/139, on Ōtata Island in the Hauraki Gulf, New Zealand, is a stratified site with dates spanning most of the pre-European occupation of New Zealand (cal 1350–1800 CE). This provides a rare opportunity to examine potential anthropogenic changes in the pre-European marine environment. Snapper ( Chrysophrys auratus ) otoliths from three midden layers were analysed for barium (Ba) and strontium (Sr) composition with Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) and the resulting data for the first 1500 µm from the core, roughly equivalent to the first two years of the fish’s life, were analysed with Behavioural Change Point Analysis (BCPA). This showed that juvenile snapper behaviours did not change but that Ba concentrations in the second year of life did. This is attributed to anthropogenic landscape changes altering the hydrology of the zone where freshwater mixes into the marine waters of the gulf.