July 14, 2011

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


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