Sacramento River Clam Survey

We investigated the presence, distribution, and abundance of invasive clams in the Sacramento River between Sacramento and Isleton in 2013 and 2014.

Invasive clams graze on phytoplankton and compete for food with native Delta organisms. Clam and zooplankton grazing are known to limit phytoplankton abundance in the Low Salinity Zone (LSZ) of the Bay-Delta system (near Suisun Bay, between Martinez and Pittsburg). In the LSZ, clams and microzooplankton can consume phytoplankton faster than it is produced, and at some locations in the Sacramento River clams can filter approximately 50 percent of the river’s water per day.


Results show that non-native clams (Corbicula fluminea) were present at all 11 stations. A total of approximately 18,000 clams were collected each year, with approximately 315 clams per 32-yard trawl. Lower clam abundance was observed downstream of the SRWTP discharge; this may be related to the lower phytoplankton biomass observed in that section of the river (see river survey).

This research is now published in the scientific journal Limnology and Oceanography and is available “open source”:

A river-scale Lagrangian experiment examining controls on phytoplankton dynamics in the presence and absence of treated wastewater effluent high in ammonium. 2017. Tamara E. C. Kraus, Kurt D. Carpenter, Brian A. Bergamaschi, Alexander E. Parker, Elizabeth B. Stumpner, Bryan D. Downing, Nicole M. Travis, Frances P. Wilkerson, Carol Kendall, Timothy D. Mussen. Limnology and Oceanography. Volume 62, Issue 3, Pages 1234–1253.