Vernal Pool Fairy Shrimp

Kids' Species Information

Vernal Pool Fairy Shrimp

STATUS

Threatened. This means that we are worried about the species but it is not in danger of extinction right now.

Teen dipping for fairy shrimps

Photo: Harry Mossman, USFWS

DESCRIPTION

You probably have seen very tiny shrimps in salads. Fairy shrimps are about that size. They are from about 11 to 25 millimeters long. (About 0.4 to 1 inch) They live in vernal pools. (see Habitat below)

"Fairy" comes from fairy shrimps' delicate, almost transparent bodies and graceful movement. They swim upside down.

FOOD

Fairy shrimp feed on smaller plants and animals. These include algae, bacteria and protozoa. They also eat decaying parts of plants and animals.

HABITAT

Vernal pools can be as small as a large puddle. They can be as large as a small lake. They range from clear rock pools to muddy grassland pools. They fill during fall and winter rains.

Most vernal pool fairy shrimp live in grassland pools. They live in pools that dry up quickly. So they reproduce quickly too.

In the spring, vernal pools have beautiful wildflowers that form rings. Some endangered vernal pool plants include:

  • Baker's stickyseed RTF
  • Burke's goldfields RTF
  • Butte County Meadowfoam RTF
  • Contra Costa Goldfields
  • Loch Lomond Coyote-Thistle
  • Sacramento Orcutt Grass
  • Many-Flowered Navarretia

See Kids' Splash page for more plants.

PREDATORS

Birds, bugs, beetles and other larger creatures. The endangered vernal pool tadpole shrimp is one of those predators.

RANGE

Vernal pool fairy shrimp are scattered throughout the Central Valley. They also live in the coastal mountain ranges. Isolated groups live in southern California and Oregon.

REPRODUCTION

Most vernal pools dry up completely in the summer. What happens to the fairy shrimps? They die. But many of the females have laid eggs. The eggs are called cysts. These can withstand heat, cold and drying. They hatch when the pools refill.

THREATS

Vernal pools once covered 22 million acres of California and Oregon. Changes such as the growth of cities and farming have destroyed about 75% of them. Habitat loss is the greatest threat to vernal pool species.

Other threats include invasive species, erosion and contamination. Cattle grazing can hurt or help. Cattle can help remove nonnative plants. But overgrazing can damage native plants and vernal pools.

WHAT YOU CAN DO

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

EXPLORE

Identifying types of fairy shrimps takes training. And catching them requires a permit. But you may be able to see them swimming around.

With a copy of Pond Life (See More Reading below), you can identify lots of pond animals.

MORE READING

Pond Life: A Guide to Common Plants and Animals of North American Ponds and Lakes by George K. Reid. Golden Books. A tiny, inexpensive book that is a must for anyone studying ponds.

Fairy Shrimps of California's Puddles, Pools, and Playas is written in a friendly style. There are lots of technical terms. But the authors, Clyde Eriksen and Dento Belk, carefully explain them. The book is published by Mad River Press, Eureka, CA. 1999.

Splash has lots of information. There is a video that gives a good overview of vernal pools.

Photo Credits: Fairy shrimp—Dwight Harvey. Teen dipping—Harry Mossman. Linked photo of flower rings at Phoenix Field Park in Sacramento—Dwight Harvey. Linked photo of dried up pools at Carrizo Plain—Adam Zennerer. All photographers—U.S. Fish & Wildlife Service.

Words to Learn

Biologists call vernal pool fairy shrimp branchinecta lynchi. Scientific names are in Latin or Greek.

Vernal pool fairy shrimp are in the Branchinectidae family.

See the Splash glossary for definitions of other technical words.