Testing Scenarios for Archaeological Mussel Collection in South Africa

Stranded rocky shore mussels and their possible procurement during prehistory on the West Coast of South Africa

Author:

Jerardino

Abstract:

A number of competing or complementary approaches are often used to understand patterns in shellfish abundance in the archaeological record. The relative importance of environmental, behavioural or taphonomic factors lends support to these different models. In the context of South African West Coast shell middens, the procurement of washed-up (stranded) fauna (vertebrates and invertebrates) has been proposed as a possible subsistence adaptation since the Late Pleistocene. The collection of washed-up rocky shore mussels (Choromytilus meridionalis), particularly, has been suggested to account for shellfish species composition in West Coast sites. The objective of this paper is to test this scenario by means of field observations from natural assemblages (washed-up mussels and storm beach accumulations) and archaeological observations from ten late Holocene assemblages. Metrical observations of C. meridionalis shells are interpreted in terms of updated knowledge on the biology and ecology of this species and used to bring insight into the procurement of this species. This study shows that less than half of stranded mussels are edible, and that considerable search/handling costs are involved when procuring this source. Because of their low returns and unpredictability, mussels are much more likely to have been collected from exposed rocky reefs than from washed-up material.

Native Americans in British Columbia Practiced Aquaculture Through Clam Gardens

Ancient Clam Gardens Increased Shellfish Production: Adaptive Strategies from the Past Can Inform Food Security Today

Authors:

Groesbeck et al

Abstract:

Maintaining food production while sustaining productive ecosystems is among the central challenges of our time, yet, it has been for millennia. Ancient clam gardens, intertidal rock-walled terraces constructed by humans during the late Holocene, are thought to have improved the growing conditions for clams. We tested this hypothesis by comparing the beach slope, intertidal height, and biomass and density of bivalves at replicate clam garden and non-walled clam beaches in British Columbia, Canada. We also quantified the variation in growth and survival rates of littleneck clams (Leukoma staminea) we experimentally transplanted across these two beach types. We found that clam gardens had significantly shallower slopes than non-walled beaches and greater densities of L. staminea and Saxidomus giganteus, particularly at smaller size classes. Overall, clam gardens contained 4 times as many butter clams and over twice as many littleneck clams relative to non-walled beaches. As predicted, this relationship varied as a function of intertidal height, whereby clam density and biomass tended to be greater in clam gardens compared to non-walled beaches at relatively higher intertidal heights. Transplanted juvenile L. staminea grew 1.7 times faster and smaller size classes were more likely to survive in clam gardens than non-walled beaches, specifically at the top and bottom of beaches. Consequently, we provide strong evidence that ancient clam gardens likely increased clam productivity by altering the slope of soft-sediment beaches, expanding optimal intertidal clam habitat, thereby enhancing growing conditions for clams. These results reveal how ancient shellfish aquaculture practices may have supported food security strategies in the past and provide insight into tools for the conservation, management, and governance of intertidal seascapes today.