California Sea Grant College Program

The detection of dwarf eelgrass (Zostera japonica Aschers and Graebn) in Humboldt Bay, California, in June 2002 represents the southern extent of its range in the Eastern Pacific and it is the first time this introduced species has been encountered in California. Z. japonica is capable of rapid expansion over non-vegetated mudflats, and the species has become well established in estuaries throughout Washington and Oregon (Baldwin and Lovvorn 1994, Bulthuis 1992, Dudoit 2006). The Z. japonica population in Humboldt Bay was monitored from June 2002 through April 2003, and the plants exhibited exponential growth (Schlosser et al, in prep).

Eradication efforts were initiated in April 2003 by a team of volunteers coordinated by U.C. Sea Grant Extension in collaboration with the California Department of Fish and Game (DFG). Since April 2004, on-going monitoring and eradication has been made possible through grant funding provided by the National Fish and Wildlife Foundation. Expenses covered by grant funds have included U.C. Sea Grant Extension staff time, student interns, and field supplies. Contributions to the project include DFG staff time and DFG boat use. This report documents the work accomplished for the period April 1, 2004 through November 30, 2007. A new grant provided by DFG will allow the project to continue starting December 1, 2007.