Can Mussels Make a Comeback?

“Freshwater mussels play a little-known role in our daily lives. They sit at the bottom of rivers for years, filtering and cleaning our waters...”

Jeanette Howard, associate director of science for fresh water for The Nature Conservancy in California

Jeanette Howard, our associate director of science for fresh water, has spent the past 15 years (off and on) studying mussels, seeking to better understand their role in the river ecosystem. The work requires diving into the best—and worst—of the state’s rivers, from the pristine to the polluted. Yet Dr. Howard feels lucky to work with rivers: “In California, our water is gold. It’s precious.”

They were once the backbone of the button industry, but the advent of plastic rendered freshwater mussel harvesting nearly obsolete,” says Jeanette Howard.

It was like a fighter’s one-two punch: As commercially raised mussels took their hit, wild freshwater mussels were next to receive a serious blow. Once accounting for the largest presence—whether plant or animal—in some streams, their numbers have dramatically dwindled.

Diminishing fish populations—these mussels rely on fish as hosts for their larvae—and increasingly polluted waters have taken their toll on these essential bivalves.

Nature’s Water Filters

“Freshwater mussels play a little-known role in our daily lives,” says Howard. “They sit at the bottom of rivers for years, filtering and cleaning our waters much like oysters do in estuaries. They even absorb parasites like giardia.”

And if that’s not enough, they produce a compost-like material that nourishes other stream animals, contributing to the overall health of our freshwater systems.

Mixed News for Mussels

Howard is teaming up with the U.S. Forest Service on the first-ever comprehensive statewide mussel study. Slipping into her wetsuit, snorkel and mask, she’s busy diving at historical sites dating back to the mid-1800s to assess our freshwater mussel population.

In 75 percent of the places Howard has investigated, mussel populations are still present. Unfortunately, many of southern California’s streams are barren, due to development, pollution or cement.

We’re Having an Effect

Most reassuring is that Howard is discovering that those streams and rivers that have been protected have amazingly robust mussel populations.

“Protecting and restoring our waterways is working!” exclaims Howard. “Of the more than 100 sites I’ve surveyed, the Conservancy sites have the greatest abundance and diversity of mussels throughout the state.”

Freshwater mussels are important in this state, where our water is so precious. They benefit from all our planning and protection efforts. And they, in turn, help so many other creatures, including us.”

Facts About Mussels:
  • An ancient species. Distant cousins of marine mussels, freshwater mussels entered our rivers and lakes from coastal waters millions of years ago.
  • Hitchin’ a ride. Some species of mussels mimic an insect or a minnow to attract a fish. When the fish strikes at the mussel, it releases thousands of mussel larvae onto the fish’s gills or fins, where they can grow for up to two months.
  • Long in the tooth. Some species of mussels can live to be more than 100 years old and grow to over a foot in length.
  • These aren’t your mother’s zebra mussels. California freshwater mussels are not the same species as the invasive zebra or quagga mussels, which do not need a host fish and reproduce at a tremendous rate. They compete for food and take over entire ecosystems.
  • Mussel business. Native Americans used them for food, tools and jewelry. In the last century they’ve also been used to make buttons and to culture freshwater pearls.
  • That has a nice ring to it. Mussels are excellent indicators of water quality. Like trees, their shells grow rings that tell of past environmental disturbances—even showing when El Niño has happened!
  • Creatures of habit. Their life cycle has gone unchanged for millions of years, so they can’t adapt to abrupt and sudden impacts on their habitats.
  • On the ropes. They are the most imperiled group of species in North America. From a group of almost three hundred species, 7% have become extinct in the last fifty years, and 65% are threatened or endangered.


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