Non-Native Invasive Species of Concern in 
San Francisco Bay-Delta  

A wide variety of aquatic NIS have found their way into the San Francisco Bay-Delta. Unfortunately, in most cases it is impossible to pinpoint exactly how a species first came into the area. Listed below are some serious aquatic pests that are currently plaguing the Bay-Delta and possible pathways by which they were introduced.

Asian Clam (Potamocorbula amurensis): Reduces blooms of floating algae that are necessary to support native invertebrates and fishes. Achieves extremely high densities and displaces native organisms. May have been introduced with ballast water.

Atlantic Smooth Cordgrass (Spartina alterniflora and hybrids): Overgrows mudflat habitats needed by wintering shorebirds, and hybridizes with and eliminates native cordgrass. Intentionally introduced into San Francisco Bay for marsh restoration.

Chinese Mitten Crab (Eriocheir sinensis): Clogs fish salvage facilities, creates losses for fisheries, and is a potential vector for human lung fluke. Commercially valuable and may have been introduced to establish a new fishery or possibly via ballast water.

European Green Crab (Carcinus maenas): Dramatically reduces native clams and shore crabs, and threatens regional shellfish production. Potentially introduced from the eastern U.S. with packing material for lobsters or bait worms, or perhaps via ballast water.

Inland Silverside (Menidia beryllina): Consumes and competes with native fishes including endangered delta smelt. Intentionally introduced outside of the Bay-Delta for aquatic insect control, but its spread into the Delta was likely aided by unauthorized releases.

Water Hyacinth (Eichhornia crassipes): Clogs waterways, impairs recreational boating, and interferes with irrigation and power generation. A popular horticultural plant that may have spread from backyard ponds.

We do not know how the next new aquatic species will enter the Bay-Delta or whether it will have negative impacts. Therefore, we must all work towards minimizing the potential for introduction through all known pathways.

---

This is a partial list of problematic plants and animals that can be found in the San Francisco Bay-Delta as well as some highly invasive species that may arrive here. Learn to identify these species so any new introduction may be detected and reported EARLY! Early detection is the key to a Rapid Response.

Invasive Species in California Now		Invasive Species Not Known to be in California
Animals	Plants	Animals	Plants
African Clawed Frog (Xenopus laevis)	Brazilian Waterweed (Egeria densa)	Asian Swamp Eel (Monopterus albus)	Ambulia (Limnophila sessiliflora) Currently found only in rice fields. Check the Center for Aquatic and Invasive Plants for more information.
Asian Clam (Potamocorbula amurensis)	Caulerpa (Caulerpa taxifolia) read this summary (may arrive in SFBD)	Channeled Apple Snail (Pomacea canaliculata) Currently found in rice fields	Anchored Water Hyacinth (Eichhornia azurea) Check the Center for Aquatic and Invasive Plants for more information.
Asian Clam 2 (Corbicula fluminea)	Eurasian watermilfoil (Myriophyllum spicatum)	Green Sunfish (Lipomis cyanellus)	Arrowhead (Sagittaria sagittifolia) Check the Center for Aquatic and Invasive Plants for more information.
Bullfrog (Rana catesbeiana)	Arundo or Giant Reed (Arundo donax)	Northern Pacific Sea Star (Asterias amurensis)	Exotic Bur-reed (Sparganium erectum> Check the Center for Aquatic and Invasive Plants for more information.
Chinese Mitten Crab (Eriocheir sinensis)	Hydrilla (Hydrilla verticillata)(may establish in Delta)	Nuclear Worm (Namalycastis abiuma)	Oxygen Weed Lagarosiphon major
European Green Crab (Carcnius maenas)	Purple Loosestrife (Lythrum salicaria)	Snakehead (Channa micropeltes)	Water Chestnut (Trapa natans) Check the Center for Aquatic and Invasive Plants for more information.
Inland Silverside (Menidia beryllina)	Saltcedar (Tamarix ramosissima)	Zebra Mussel (Dreissena polymorpha)	Water Soldier (Stratiotes aloides) Check the Center for Aquatic and Invasive Plants for more information.
Largemouth Bass (Micropterus salmoides)	Salvinia (S.auriculata complex, Salvinia auriculata, S. biloba, S. herzogii and S. molesta)		Water Velvet (Azolla pinnata) Check the Center for Aquatic and Invasive Plants for more information.
Mediterranean Mussel (Mytilus galloprovincialis)	Atlantic Smooth Cordgrass (Spartina alterniflora)
New Zealand Mud Snail (Potamopyrgus antipodarum)	Water Hyacinth (Eichhornia crassipes)
Shipworm (Tereda navalis)	Water Lettuce (Pistia stratiotes)
South African Sabellid Worm (Terebrasabella heterouncinata)	Yellow Flag Iris (Iris pseudacorus)
	Salt Meadow Cordgrass (Spartina patens)

return to home page

*RIDNIS Project Species of Concern Page, September 2003 - September 2005 (*Reducing the Introduction and Distribution of Aquatic Non-Native Invasive Species through Outreach & Education) University of California Cooperative Extension, Department of Environmental Science and Policy

This project is funded by the CBDA California Bay-Delta Authority in cooperation with the University of California Cooperative Extension.