Using archaeological otoliths to determine palaeoenvironmental change and Ngarrindjeri resource use in the Coorong and Lower Murray, South Australia

22nd April 2013

Morgan Disspain

BArchaeology(Hons), Department of Archaeology, Flinders University, October 2009

Increasing collaborations between archaeologists, marine ecologists and other scientists are developing new methods for recognising and measuring the impacts that Indigenous people had on coastal environments. One particularly promising avenue of research for achieving this is through the study of otoliths (fish ear bones). Otoliths can be identified to species level, record the age and growth of a fish from the date of hatching to the time of death, and, through trace element analysis, allow the reconstruction of palaeoenvironmental conditions including water temperature and salinity. Otoliths recovered from the archaeological record can provide valuable archives of ecological patterns, climate change and by inference, associated human responses. However, most analyses of archaeological otoliths in Australia to date have focussed on identifying only the species and sometimes the age of the fish, with more detailed geochemical studies not pursued.

This thesis presents results from a pilot study of archaeological otoliths from middens along the Coorong (n=23), and Lower Murray River (n=14), dating from the mid-to-late Holocene. Results demonstrate that the majority of the fish (identified as Argyrosomus japonicus and Acanthopagrus butcheri in the Coorong, and Maccullochella peelii peelii and Macquaria ambigua in the Lower Murray) were caught in freshwater environments during the warm season, and had grown to an age and size indicative of sexual maturity. These observations accord with Ngarrindjeri oral tradition concerning sustainable management strategies. However, despite the implementation of such strategies, human predation had an impact on the population dynamics of the dominant species. It is tentatively suggested that A. japonicus experienced a decrease in fish size and an increase in fish age over time, and Maccullochella peelii peelii experienced a decrease in both fish age and size through time, with the larger of the two species struggling to recover from population decline.

This study provides data supporting the argument that people have significantly altered the waterways of the Coorong and Lower Murray. Trace element data of otoliths associated with dates from ca 6500 BP to ca 200 BP revealed fluctuating levels of salinity in the river and the estuary significantly lower than the hypersaline conditions experienced in some areas today. The data also provide information about subsistence strategies of the Indigenous population, and their adaptations to the changing climate and resource availability. Ultimately, this project provides a foundation for further development of geochemical analyses of otoliths within archaeological investigations.

Morgan Disspain
Using archaeological otoliths to determine palaeoenvironmental change and Ngarrindjeri resource use in the Coorong and Lower Murray, South Australia
June 2010
Thesis Abstracts
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