Australian Aboriginal freshwater shell middens from late Quaternary northwest Victoria: Prey choice, economic variability and exploitation

The Central Murray River Valley in northwest Victoria contains a rich and diverse archaeological history spanning the last 20,000 years, which has the potential to help inform on past human behaviour and subsistence strategies. In particular, freshwater shell middens are important as they can provide information about the local aquatic economy, and the role of these molluscs in the diet of Aboriginal hunter-gatherers. Many of the middens in the region consist of thin temporal horizons while being laterally expansive in size (some measuring up to 400 m in length). These middens are dominated by two aquatic molluscs: the river mussel Alathyria jacksoni and the river snail Notopala sublineata. However whilst it is generally accepted that Alathyria jacksoni was a common human prey species, it is thought that the smaller gastropod Notopala sublineata was collected accidentally as by-catch and was not economically important. To investigate, two spatially and temporally distinct middens from different land-systems spanning the late Pleistocene to the late Holocene were studied to look at the variety and size of mollusc species. To supplement the archaeological record, the potential economic and nutritional quality of the bivalve Alathyria jacksoni was investigated. The nutritional results indicate that while Alathyria are low in fat (but are good sources of omega 3- and 6-fatty acids), they are high in protein and calorific energy (kj), and are excellent sources of magnesium (Mg), Iron (Fe), Sodium (Na) and Zinc (Zn). These results coupled with the modern behavioural ecology of these freshwater molluscs, as well as ethnographic and modern cooking experiments, help identify human foraging and subsistence strategies in this region. Results indicate that despite earlier ideas, the river snail Notopala sublineata was an important economic aquatic resource during the late Pleistocene and Holocene.