San Pablo Bay National Wildlife Refuge
Map SatelliteThis Refuge, which extends across the northern part of the San Pablo Bay from Ware Island to the mouth of the Petaluma River, is the wintering ground for up to half of the population of the canvasback duck, Aythya valisineria, of the Pacific Flyway. Among the other ducks seen here in season are mallards, Anas platyrhynchos, pintail, Anas acuta, baldpate, Mareca americana, and redhead, Aythya americana. Additionally, a variety of shorebirds and water-birds frequent the Refuge.
Two endangered species are found here, the California clapper rail, Rallus longirostris obsoletus, and the salt-marsh harvest mouse, Reithrodontomys raviventris. There is also a colony of harbor seals, Phoca vitulina, which haul out in the Refuge. (See Lower Tubbs Island Reserve)
On the extensive mudflats there is an abundance of various species of clams, mussels, snails, worms and other invertebrates.
Approximately 1,940 hectares (4,800 acres) are in open water, nearly 2,000 hectares (5,000 acres) in tidal mudflats, 690 hectares (1,700 acres) in salt marsh, and about 115 hectares (290 acres) in freshwater-brackish marsh.
The dominant vegetation in the salt marsh is pickle-weed, Salicornia spp., and salt grass, Distichlis spicata, with some cord grass, Spartina foliosa. Various algal forms are found on the mudflats. Bulrush, Scirpus sp., is the dominant in the freshwater-brackish marsh.
Quaternary alluvial deposits comprise the entire area in the Bay; these deposits may exceed 200 meters (700 feet) in thickness. Up to 30 meters (100 feet) of surface mud covers these layers in places.
Integrity: Much of the area is relatively undisturbed, though there are some levees, primarily on the inland portions of the perimeter, several abandoned duck blinds, and on Tubbs Island some buildings. It is managed as a Wildlife Refuge.
Use: Research, educational, observational, light recreational.
May 1976
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman