Can’t Live Without ‘Em: Vernal Pool Fairy Shrimp

A weekly homage to endangered species, large and small


(Original text by Ben Ikenson)

Vernal Pool Fairy Shrimp are small crustaceans related to lobsters, crabs and their much larger cousins that taste so good in gumbo. Although the name might sound like a magical creature from a fantasy world like Never Never Land, these shrimp were added to the threatened and endangered species list in 1994—a story quite opposite of a fairytale.

The fairy shrimp (“fairy” because of their diminutive stature and translucent bodies) are known to live only in the seasonal rain ponds (called vernal pools) of central California, and recently a small population was found in southern Oregon.

These tiny invertebrates live only a few weeks when late winter rains flood grasslands and forest to fill the vernal pools for the shrimp to flourish in. As spring turns to summer, mature females lay eggs before the pools dry up completely. The eggs sit in the dry mud during the summer and freeze over during autumn and early winter. Then when the rains return, miraculously the weather-beaten eggs hatch to repeat the same process.

Because vernal pools dry up seasonally, fish generally can’t live in them. As a result amphibians, insects and fairy shrimp can thrive and maintain large populations.


Unfortunately, the rapid pace of urban and suburban development in California has altered or destroyed many of these habitats. Highway construction also leads to water runoff from roadways and changes in soil composition, which can completely devastate vernal pools.

Thanks to dedicated recovery efforts under the Endangered Species Act, federal and state governments are taking actions to save the species before it’s too late.  In 2005, the U.S. Fish and Wildlife Service published a comprehensive Recovery Plan for Vernal Ecosystems in California and southern Oregon. The plan set aside areas for federal protection and called for study of many plants and animals, including several shrimp species. Findings showed that the vernal pool fairy shrimp was found across a greater range than other shrimp species in the recovery plan. However, it was uncommon throughout this larger range and rarely abundant in the locations where it was found. Ecologist and USFWS recognized fairy shrimp expert—Brent Helm, published an earlier study in 1998 which showed that only 16% of all the vernal pools tested in 27 counties contained populations of fairy shrimp.


Cartoon by Bruce Plante

Scarce numbers are a bad sign because this very small animal plays a big role in the ecosystem. On their long and arduous flights from as far away as South America to Alaska, migratory waterfowl such as Canada geese, great blue heron, tundra swan, mallards and pintails make pit stops at California’s vernal pools. To these weary travelers, the pools are like long-awaited highway exits that bear the promise of food, fuel and lodging. High in protein, the little crustacean with the whimsical name is an important food source for the journeying birds, as well as the local crowd of insects, crustaceans and amphibians.

Furthermore the shrimp act as custodians for the vernal pools. Usually no more than an inch long, the shrimp swim upside down and use their 11 sets of legs to collect algae, bacteria, protozoa and other microorganisms from the surface of the water. In essence, the shrimp keep the pools tidy and clean. As a result, their presence is a strong indicator of a healthy vernal pool ecosystem that supports countless other species.

Click to learn more about Vernal pool fairy shrimp

11 Responses to “Can’t Live Without ‘Em: Vernal Pool Fairy Shrimp”

  1. Alex

    Fairy shrimp are found in way more areas than just California and Oregon. I live in Mass and I have witnessed them in vernal pools around here every spring.

    • Richard Hill

      Fairy shrimp are found world wide. Brine shrimp, like the kind sold in aquarium stores are a salt-loving fairy shrimp. They were recognized as the key to good tasting salt from ponds ans so were moved everywhere. But some kinds of fairy shrimp are known only from a few areas, and those rare species have been protected where their pools are threatened, such as in the California vernal pools. New England “vernal” pools have protected frog species and as far as I know, the fairy shrimp are not protected.

  2. John

    Your vastly exaggerating how endangered fairy shrimp are. I worked a few months as an assistant for one of the businesses that studies fairy shrimp populations as the scuttlebutt is that the darn things are everywhere and it takes a lot of chlorine to even temporarily stunt their abundance. About the only reason the biologists can justify their continued employment as fairy shrimp conservationists is that they’ve claimed certain types of fairy shrimp are rare and therefore endangered though I suspect that types of fairy shrimp is somewhat equivalent to race in humans. Even if it’s true that these types are separate and distinct species I doubt that waterfowl actually care about anything other than the total abundance of shrimp.

    • Richard Hill

      It sounds as though you may have gained some limited knowledge but not enough to understand the issues. Species that are protected through listings are only protected after considerable public vetting of the evidence and public review. “Just-so” stories seem to drive much public discussion but carry little weight in the process.

  3. Barb Rupers

    I have lived in three areas where I have found fairy shrimp in fresh water vernal habitats: Moscow, Idaho along the railroad tracks between there and Pullman WA in the early 1950s; near Whitefish, Montana in the late 50’s; and in a Corvallis, Oregon city park puddle about 1978. They were all about 2 cm long; translucent, back swimmers; with females carrying egg pouches on their posterior swimmerets.
    Any idea as to the genera and/or species of these crustaceans? I have checked the Montana crustacean web site and found nothing that fit what I saw there.
    They were so numerous in Moscow that I used to collect them in the spring and feed them to my aquarium fish.
    !978 was the last time I observed this fascinating shrimp.

    • Richard Hill

      Hi Barb. Hard to guess after so many years. Things to consider would be Branchinecta, Eubranchipus and Streptocephalus. The Montana Field Guide has some good photos, but in life you don’t see the details easily, especially when the shrimp are translucent. Colors can vary. Sometimes they are like butterflies in their colors. It seems likely that some species from the Palouse are gone, given agricultural water withdrawals and the loss of surface pools. Railroad right of ways are invasion pathways where cattle cars are common.

  4. Sharla

    Cool article. The only reason I am reading about fairy shrimp is I recently bought one of the Smithsonian troops kits,and after looking at many pictures, i knew that what I have aren’t troops. Come to find out, I have fairy shrimp.My question is how do I know if the ones I have are the endangered ones or not? I have about 70 recently hatched babies.

    • Richard Hill

      Hi Sharla. I’m going to guess that you hatched your shrimp in a warm place? If so, there is a good chance that the shrimp are Streptocephalus or Thanmocephalus species. Look for a paddle shape at the tail end. If you hatched the shrimp at cool temperatures, then you may have Branchinecta species. It seems unlikely that you have endangered or threatened species. Hatching in a cool place would be a possible reason for not finding Triops. When the Triops do hatch, they quickly eat the fairy shrimp and anything else they can grab.

  5. Nick

    I live in western Massachusetts and have a verbal pool behind my backyard. For over 20 years the brine shrimp/fairy shrimp have showed up every year! If the owners of the land try to demolish the habitat who do I call?

  6. Luresa Byrne

    I live in California at the north end of Malibu Canyon and we are facing a crossroads here in the Santa Monica Mountains…..irresponsible development is threatening so many species and could destroy a major watershed, wetlands, and natural springs with water at the surface year round. How does a person find the appropriate biologist/scientist to visit these springs to investigate the possible evidence of endangered or protected species. We have “red-legged frogs” here and they are on the protected list. Thank-you for all the good work for our planet.

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