Mussels gathered by recreational harvesters from California’s ocean shore should not be consumed by humans for the next six months, officials warn.

Four freshwater mussel species now have additional federal protections as the U.S. Fish and Wildlife Service designates over 3,800 miles of rivers as critical habitat.

Mussels attach to rocks, ships and other structures underwater using small hair-like fibres called byssus threads. These contribute the most to the mussel’s ability to cling to a surface despite getting pounded by crashing waves.

Colorado Parks and Wildlife is ramping up vessel inspections to prevent the spread of invasive zebra mussels, which have already been detected in the Colorado River and Highline Lake.

Golden mussels are small with slightly yellow shells. They arrived in North America in 2024, hitchhiking via boat from China to the Port of Stockton. Just one mussel can produce a million offspring in a year.