Publications
Read our latest publications from this research.
Fish nearshore habitat-use patterns as ecological indicators of nursery quality
Anthropogenic factors have been identified as major stressors of nearshore environments such as estuaries, sea grass meadows and mangroves. We hypothesize that aquatic organisms functionally dependent on these habitats as nurseries respond to disturbances with subtle changes in their habitat-use patterns. We used a novel approach coupling behavioural change point analysis with fish otolith microchemistry to analyse continuous life history information independent of climate and physiological variability. Here we show that pre-industrial (1430–1640 CE) land use and fishing practices had little influence on the well synchronized migration behaviour of juvenile snapper Chrysophrys auratus in the Hauraki Gulf, New Zealand. In contrast, modern human disturbances have resulted in snapper spending less time in brackish nurseries and moving chaotically between habitats. Today, nearshore habitats have largely lost their nursery function for the species. Temporal comparison of habitat-use patterns is a powerful tool to evaluate past and present nursery habitat quality.
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.
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