Humboldt Bay National Wildlife Refuge

Five separate areas in Humboldt Bay are included in this refuge; the salt marshes on the eastern edge of North Humboldt or Arcata Bay, Sand Islands, Gunther Island, the southern portion of Arcata Bay (see also Eureka Slough), and the southern section of Humboldt Bay from the channel south. Several habitat types are present.

In Arcata Bay the Sand Island area is primarily mudflats with several sandy islands. These islands serve as a breeding area for Caspian terns, Hydroprogne caspia, and cormorants, Phalacrocorax spp. The other two areas in Arcata Bay (Gunther Island is treated separately) are primarily mudflats fringed with salt marshes. The mudflats support various algae and some eel grass, Zostera marina. In the salt marshes cord grass, Spartina foliosa, pickleweed, Salicornia virginica, and salt grass, Distichlis spicata, are the dominants, with arrow-grass, Triglochin maritima, and salt rush, Juncus lesueurii, present, among others.

Much of South Humboldt Bay is shallow water, with extensive mud flats exposed at low tide. The dominant vegetation in this area is eel grass and widgeon grass, Ruppia maritima, with various algae present, including Smithora naidum, Enteromorphia sp., and Polysiphonia sp.

On the low dunes of the south spit, vegetation is sparse and consists primarily of European dune-grass, Ammophila arenaria, and beach strawberry, Fragaria chiloensis, among others. During exceptionally high water and storms the ocean may enter directly into this part of the bay, rather than through the main channel. There are several freshwater marshes, primarily in the South Bay.

Two rare plants occur within the refuge, Castilleja ambigua ssp. humboldtiensis and Cordylanthus maritimus.

Humboldt Bay is an important part of the Pacific Flyway. Over 100 water-oriented birds occur here. Noteworthy are the black brant, Branta nigricans. The major share of the North American population utilizes the South Bay during migration, with as many as 100,000 birds on the bay at the height of the season. Some 25 species of ducks use the bay, primarily Arcata Bay. The most common is the widgeon, Mareca americana, followed by pintail, Anas acuta, and various diving ducks. The endangered California clapper rail, Rallus longirostris obsoletus, inhabits the salt marshes.

Harbor seals, Phoca vitulina, have hauling grounds and pupping areas within the bay. The harbor porpoise, Phocaena phocaena, is a regular visitor. Ninety-five species of fish have been recorded here. Over 150 species of invertebrates have been found in the bay, including 10 edible clams. The bay is an important nursery for the English sole, Parophrys vetulus, and the Dungeness crab, Cancer magister.

In the Mid and Upper Pleistocene the bay extended from the Wad River bluffs to those south of the Eel River near Centerville. (See Eel River Delta.)

Integrity: Only two areas are now protected; Sand Island, Gunther Island and South Bay are in various ownerships, and all of the areas have suffered disturbances in varying degrees.

Use: Research, educational, observational, hunting, fishing.

Ref: Monroe, Gary, 1973. The Natural Resources of Humboldt Bay, Calif. Dept. of Fish & Game, 158 pp.

August 1977