Longhorn Fairy Shrimp

Branchinecta longiantenna

Description

Branchinecta longiantenna (longhorn fairy shrimp), a member of the family Branchinectidae, was described from specimens collected at Souza Ranch in the Kellogg Creek watershed, about 22 mi (35 km) southeast of the city of Concord, Contra Costa County.

The earliest known collections of the longhorn fairy shrimp were made in 1937. It ranges in size from 0.5-0.8 in (12.1-20.8 mm). This species differs from other branchinectids in that a portion of the distal segment of its antennae is flattened in the antero-posterior plane rather than the latero-medial plane.

Behavior

The longhorn fairy shrimp has been observed from late December until late April.

Habitat

The longhorn fairy shrimp inhabits clear to turbid grass-bottomed vernal pools in grasslands and clear-water pools in sandstone depressions. All vernal pools inhabited by this species are filled by winter and spring rains and may remain inundated until June. The water in grassland pools inhabited by this species has very low conductivity, total dissolved solids, and alkalinity.

Distribution

This species is known only from four disjunct populations along the eastern margin of the central coast range from Concord, Contra Costa County south to Soda Lake in San Luis Obispo County: the Kellogg Creek watershed, the Altamont Pass area, the western and northern boundaries of Soda Lake on the Carrizo Plain, and Kesterson National Wildlife Refuge in the Central Valley.

Threats

Other vernal pools located in San Luis Obispo County, including most of the known populations of the longhorn fairy shrimp, are located in subdivided areas with constructed roads and lots for sale and development. To date, some of the sites have been cleared and continued habitat loss is ongoing or impending. The Coastal Branch Phase II (Coastal Aqueduct) of the State Water Project, proposed by the California Department of Water Resources, annually would convey 70,000 acre-feet (86 billion l) of water from the Delta region of California to San Luis Obispo and Santa Barbara Counties. It is unclear if this source of water would allow urban development of the Soda Lake area, however, the longhorn fairy shrimp and the vernal pool fairy shrimp may be adversely affected by commercial development made possible by this project.

Conservation and Recovery

The longhorn fairy shrimp is known from habitats in Kesterson National Wildlife Refuge. This federally owned habitat should be strictly protected against any threatening influences. The longhorn fairy shrimp also occurs in habitat secured by the Nature Conservancy, a private conservation organization. Other critical habitats are on privately owned land and are severely threatened by various human activities, particularly residential development. The largest of the privately owned habitats should be protected. This could be done by acquiring the land and establishing ecological reserves, or by negotiating conservation easements with the landowners. The known populations of the long-horn fairy shrimp should be monitored, and research undertaken into its biology and habitat needs.

Contacts

U. S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office Federal
Building
2800 Cottage Way, Room W-2605
Sacramento, California 95825-1846
Telephone: (916) 414-6600
Fax: (916) 460-4619

U. S. Fish and Wildlife Service Regional Office
Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 19 Sept. 1994. "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for the Conservancy Fairy Shrimp, Longhorn Fairy Shrimp, and the Vernal Pool Tadpole Shrimp; and Threatened Status for the Vernal Pool Fairy Shrimp." Federal Register http://www.cdpr.ca.gov/docs/es/estext/fr091994.txt