Unique palaeoenvironmental records? An examination of applications and the reliability of fish otoliths in archaeological investigations

Abstract

Fish otoliths are bony structures found in the inner ear of teleost fish. Their morphological and chemical properties provide excellent environmental and anthropogenic proxies. Otolith analyses are widely employed in modern fisheries studies, and have been increasing within archaeological and palaeoenvironmental research. This thesis investigates the use of otoliths in archaeological research, and evaluates the reliability of the data obtained from such analyses. The main objectives are to: (1) overview and synthesise the development and future prospects of otolith studies in archaeology; (2) investigate the reliability of archaeological fish otoliths as proxies for environmental change through the use of experimental archaeology; and (3) explore various applications of archaeological otolith analyses by applying experimental, documentary, isotopic, trace element and morphological methods to otoliths, thereby investigating what they can tell us about past environments, fish populations, and people. The main methods of archaeological otolith analysis are overviewed and discussed; in spite of some limitations, the benefits and unique information that otolith analyses can provide ensure that they should be an important part of archaeological research. Continuing development of methods and technologies within this area will serve to increase the importance and use of otoliths. An experimental approach is used to investigate the reliability of analyses of archaeological fish remains, specifically the effects that cooking and processing methods have on the morphology and chemistry of hard parts. Analyses of otoliths, vertebrae and scales from mulloway (Argyrosomus japonicus) cooked using a range of techniques reveal disparities in the chemistry and morphology of otoliths and vertebrae processed in different ways, while impacts observed in the fish scales were less substantial. Findings highlight the need to conduct palaeoenvironmental reconstructions based on chemistry and stable isotope data of archaeological fish remains with caution. Otoliths from two archaeological sites in the Atacama Desert, Chile were analysed; species distribution and changes over time were investigated, and fish size was estimated based on relationships between otolith weight and fish total length (TL) determined from modern samples. These analyses provide insights into the subsistence strategies of past site inhabitants, as well as how fish populations in the region have changed over time. Comparisons with a nearby contemporaneous site, suggest that fishing techniques were similar along this section of the Pacific coast. Fish age, size and growth data obtained from archaeological fish otoliths, historical anecdotes, and contemporary data sources were combined to provide an extended temporal record of mulloway, A. japonicus, populations along the eastern coast of South Australia. Data from the three different sources corroborate each other in many aspects, with no significant changes in fish length over time evident, at least for the time span of the three data sources, demonstrating the benefit of combining data sets from extended time periods to examine fish survival over thousands of years. Accelerator Mass Spectrometry (AMS) radiocarbon dates on archaeological otoliths extend the known period of occupation of Long Point, Coorong, South Australia. They provide a detailed local chronology for the region, contributing to a more comprehensive understanding of human use of the area, and validate the use of fish otoliths for radiocarbon dating. The research presented in this thesis reviews the use of otoliths in archaeological research, assesses the reliability of palaeoenvironmental data obtained from fish hard parts, and applies various methods of otolith analysis to archaeological assemblages.