U.S. Fish & Wildlife Service

Sacramento Fish & Wildlife OfficeServing the people, conserving the fish, wildlife, and plants of California

A Unit Of The Pacific Southwest Region

Species Information

Conservancy Fairy Shrimp

Branchinecta conservatio

Basic Species Information


Endangered. This species is in danger of extinction throughout all or a significant portion of its range.


The Conservancy fairy shrimp (Branchinecta conservatio), is a small crustacean in the Branchinectidae family. It ranges in size from about 1.3 to 2.5 cm (½ to 1 inch) long. Fairy shrimp are aquatic species in the order Anostraca. They have delicate elongate bodies, large stalked compound eyes, no carapaces, and 11 pairs of swimming legs. They glide gracefully upside down, swimming by beating their legs in a complex, wavelike movement that passes from front to back.


Fairy shrimp feed on algae, bacteria, protozoa, rotifers and bits of detritus.


Conservancy fairy shrimp inhabit rather large, cool-water vernal pools with moderately turbid water. The pools generally last until June. However, the shrimp are gone long before then. They have been collected from early November to early April.


Female fairy shrimp carry their eggs in a ventral brood sac. The eggs either are dropped to the pool bottom or remain in the brood sac until the mother dies and sinks. When the pool dries out, so do the eggs. They remain in the dry pool bed until rains and other environmental stimuli hatch them.

Resting fairy shrimp eggs are known as cysts. They are capable of withstanding heat, cold and prolonged desiccation. When the pools refill, some, but not all, of the cysts may hatch. The cyst bank in the soil may contain cysts from several years of breeding.

Hatching can begin within the same week that a pool starts to fill. Average time to maturity is 49 days. In warmer pools, it can be as little as 19.


Currently, the Service is aware of eight populations of Conservancy fairy shrimp:

  1. Vina Plains, Butte and Tehama counties
  2. Sacramento National Wildlife Refuge, Glenn County
  3. Yolo Bypass Wildlife Area, Yolo County
  4. Jepson Prairie, Solano County
  5. Mapes Ranch, Stanislaus County
  6. University of California, Merced, Merced County
  7. Grasslands Ecological Area, Merced County
  8. Los Padres National Forest, Ventura County


Habitat loss and fragmentation is the largest threat to the survival and recovery of vernal pool species. Habitat loss generally is a result of urbanization, agricultural conversion, and mining.

Habitat loss also occurs in the form of habitat alteration and degradation as a result of changes to natural hydrology, invasive species, incompatible grazing regimes, including insufficient grazing for prolonged periods; infrastructure projects (e.g., roads, water storage and conveyance, and utilities), recreational activities (e.g., off-highway vehicles and hiking), erosion, climatic and environmental change and contamination.


Just about any place you live, you can help restore streams and ponds. Search the Internet for words like volunteer, stream, river, watershed, restoration, clean-up, and the name of your town or area.

Many of the ideas in What You Can Do to Help Wildlife and Plants (201 KB | PDF) can help protect and recover streams. For example, be careful what you pour down sinks. Remember that it will end up in your community's water.

Last updated: December 1, 2017