California Freshwater Shrimp


Description and biology

The California freshwater shrimp is similar in appearance to the common marine (ocean) shrimp. It has a greenish–gray body with light blue tail fins. When seen in the water, it looks transparent. An average adult can measure up to 2.5 inches (6.4 centimeters) long.

After mating, a female California freshwater shrimp carries her eggs on her body throughout the winter. The eggs, which number between 50 and 120, grow very slowly over a nine–month period. Only about half of the eggs hatch.


Habitat and current distribution

This species of shrimp is found in three counties in California. In Napa County, it inhabits the Napa River near Calistoga. In Marin and Sonoma Counties, it inhabits Big Austin, East Austin, Blucher, Green Valley, Huichica, Jonive, Lagunitas, Salmon, Walker, and Yulupa Creeks. Biologists (people who study living organisms) do not know the total number of these shrimp currently in existence.

The California freshwater shrimp prefers to inhabit quiet, clear freshwater streams. These streams are usually tree–lined and have underwater vegetation and exposed tree roots. Water in the streams is fairly slow–moving.

History and conservation measures

The range of the California freshwater shrimp has not changed, but areas within that range where the shrimp is found have decreased. The shrimp has disappeared completely from streams that it formerly inhabited.

The primary threat to this shrimp is the loss or destruction of its habitat. Many streams in its range have been diverted or dammed to help irrigate farms. In some areas, the water quality of the streams has decreased.

Runoff from farms has introduced pesticides and other agricultural chemicals into the water system. The amount of silt (mineral particles) in the water has also increased because of construction along the banks of many streams.

Some dams have been removed in an attempt to restore the California freshwater shrimp’s habitat. To further save this species, the effects of future damming and construction projects will have to be examined.

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