Wednesday July 8, 2026
Maven’s Notebook —
The San Francisco Bay-Delta estuary has been a food desert for fish for two decades and the introduced overbite clam is a major culprit. The fish eat tiny creatures called zooplankton, which in turn eat tiny plant-like organisms called phytoplankton. But overbite clams eat so much phytoplankton that there’s hardly any zooplankton for fish.
“It’s a huge problem,” says Madison Dunlap, a University of California, Davis ecologist.
Now Dunlap and aquatic ecologist John Durand, also at UC Davis, present an out-of-the-box idea for controlling overbite clams in hopes of boosting fish food. In a June California Water Blog post, they explore dredging the clams in Suisun Marsh, which is between the Bay and the Delta.
Suisun Marsh is also a bright spot for at-risk native fish like Delta smelt, longfin smelt, and young salmon migrating toward the ocean. “It’s their last refuge,” says Durand.
CLAM INVASION
Overbite clams, so called because one shell overhangs the other, are small but mighty. These shellfish spawn year-round, starting when they’re just a couple of months old, and a single female can produce up to 220,000 eggs in her short lifetime of about two years.