The relationship between clams and humans is deeper than just chowder. We’ve been interacting with the bivalves for thousands of years, according to a new study, and the animals have actually thrived under human management.
Researchers focused on clams in the Salish Sea in British Columbia in Canada. They started out looking at populations of butter clams—small, tasty marine mollusks—that lived about 11,500 years ago before the arrival of permanent human settlers. These early clams were relatively small—about 80% the size of today’s butter clams—but they got bigger and lived longer as sea levels stabilized and glaciers receded after the end of the last ice age, leaving rocky sea floors in their wake. By 10,900 to 9500 years ago, the clams were much larger (see above).
Although nomadic people had traveled through this part of Canada in earlier centuries, regular clam harvesters arrived on the scene about 9000 years ago. Life further improved for the clams about some 5500 years later, when First Nations peoples began to cultivate the bivalves in clam gardens, the team reports today in the Proceedings of the National Academy of Sciences. The gardens featured walled-off terraces with few nonhuman predators like large fish and crabs, and plenty of phytoplankton and other mollusk meals, leading the clams to grow faster. Despite the bivalves constantly being harvested for food, the gardens kept the remaining residents happy as, well, clams.
Once Europeans arrived in the area, clam aquaculture fell by the wayside. This, in combination with warming oceans and an influx of fine-grained sand replacing their preferred rocky sea floor as a result of industrial logging, spells bad news for bivalves. To help clam populations, some conservationists advocate for more aquaculture management, and many Indigenous communities in the Pacific Northwest are restoring the traditional clam gardens.