FWS Focus



The Conservancy fairy shrimp is a small, freshwater crustacean named for The Nature Conservancy, an organization that has protected several vernal pool ecosystems in California that support the species. Conservancy fairy shrimp are restricted to vernal pools found in California’s Central Valley from Tehama County in the north to Merced County in the south. However, there is one outlying population in Ventura County’s Interior Coast Ranges. The Conservancy fairy shrimp was listed as endangered September 19, 1994.

Threats facing the species include:

  • Habitat loss, fragmentation and degradation from development and agriculture
  • Poor grazing practices
  • Non-native plants and grasses
  • Climate change and drought
  • Pesticides

Scientific Name

Branchinecta conservatio
Common Name
conservancy fairy shrimp
FWS Category

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Conservancy fairy shrimp are extremely rare and only found in California’s Central Valley. They mostly live in relatively large, turbid freshwater vernal pools called playa pools. Currently, the U.S. Fish and Wildlife Service is aware of 10 populations of Conservancy fairy shrimp:

  • Vina Plains, Butte and Tehama counties
  • Sacramento National Wildlife Refuge, Glenn County
  • Mariner Ranch, Placer County
  • Yolo Bypass Wildlife Area, Yolo County
  • Jepson Prairie, Solano County
  • Mapes Ranch, Stanislaus County
  • University of California, Merced, Merced County
  • Grasslands Ecological Area, Merced County
  • Sandy Mush Road, Merced County
  • Los Padres National Forest, Ventura County

Conservancy fairy shrimp have been found at elevations ranging from 16 to 5,577 feet (5 to 1,700 meters) above sea level. The species has been found at sites that are low in alkalinity that range from 16 to 47 parts per million.


Land on which the natural dominant plant forms are grasses and forbs.


Environments influenced by humans in a less substantial way than cities. This can include agriculture, silvaculture, aquaculture, etc.


Areas such as marshes or swamps that are covered often intermittently with shallow water or have soil saturated with moisture.

Characteristic category



Conservancy fairy shrimp are opportunistic filter feeders. They eat algae, bacteria, protozoa, rotifers and bits of waste from other plants and animals present in their environments. They face competition from other fairy shrimp species and Western spadefoot toad tadpoles.

Characteristic category

Physical Characteristics

Size & Shape

They have slender bodies; large, stalked compound eyes and 11 pairs of swimming legs. They glide gracefully through the water upside down, swimming by beating their legs in a complex, wavelike movement that passes from front to back. The Conservancy fairy shrimp can be differentiated from other fairy shrimp by the flattened portions of its antennae. Unlike other types of shrimp, the Conservancy fairy shrimp does not have a hard outer shell.

Length: 0.6 to 1.1 in (14 to 27 mm)

Characteristic category

Life Cycle

Life Span

The life span of the Conservancy fairy shrimp is about 114 days. Conservancy fairy shrimp can be found in vernal pools starting in November most years and complete their entire life cycle by April. On average, Conservancy fairy shrimp take 37 days to mature after hatching and 46 days to reproduce. Multiple cohorts of eggs may hatch in a single vernal pool throughout the wet season given the right conditions. Conservancy fairy shrimp disappear before the vernal pools dry.

Conservancy fairy shrimp are non-migratory and have little ability to disperse on their own. Aquatic birds are the most likely agents of dispersal of Conservancy fairy shrimp. Large mammals are also known to act as distributors by wallowing in dirt, getting cysts caught in their fur and transporting the cysts to another wallow. Additionally, cysts can be ingested, passed through the digestive tract and then deposited in new habitats when the animal urinates.


Female fairy shrimp carry fertilized eggs in a sac on the underside of their body. The eggs are either dropped to the pool bottom or remain in the brood sac until the mother dies and sinks to the bottom of the pool.

When the pool dries out, so do the eggs. Resting fairy shrimp eggs are known as cysts. Cysts may remain viable for multiple years due to their protective coverings that help them withstand extreme environmental conditions and even digestion by predators. The cysts remain in the dry pool bed until hatching begins in response to rains and the return of water in the vernal pools.


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