Ancient clam gardens highly productive, SFU study finds (with video)
Ancient aboriginal clam gardens dramatically boosted shellfish production by pre-contact coastal First Nations, according to new findings by SFU and University of Washington researchers.
Indigenous communities built rock-walled beach terraces to cultivate clams to help feed their burgeoning populations and the SFU-led study tested their effectiveness by transplanting hundreds of baby clams into six ancient clam gardens around Quadra Island.
They found the clams placed in ancient human-constructed terraces grew nearly twice as fast and were more likely to survive than baby clams transplanted into unmodified beaches in the same area.
"We discovered that by flattening the slope of the beach ancient clam gardens expanded the real-estate for clams at the intertidal height at which they grow and survive best," SFU ecologist Anne Salomon said.
She said traditional knowledge from modern First Nations indicates their ancestors boosted the gardens' productivity by adding ground clam shell and pebbles to them."
Four times as many butter clams and twice as many littleneck clams grew in the ancient clam gardens as did on unmodified beaches studied, according to the study published in an online peer-reviewed journal.
SFU archaeologist Dana Lepofsky said it's fortunate the team had both historic clam gardens to study and traditional cultural knowledge to guide them.
"The lessons learned here have global implications for food security and about the way indigenous people interact with their land and seascapes," she said.
The study also found some modern shellfish aquaculture practices undermine shoreline ecosystems by altering their composition, changing sediment characteristics and enabling the introduction of invasive species.
Photo above: Archaeologist Dana Lepofsky examines clams on part of Quadra Island riddled with ancient clam gardens.