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California Freshwater Shrimp cont. California freshwater shrimp (Syncaris pacifica) live in lowland perennial streams in Sonoma, Marin and Napa counties. None have ever been found higher than 380 feet above sea level. Before human impacts, the shrimp were probably common in many streams within the three county area. However, a catastrophe which greatly reduces their population can now easily lead to their disappearance from a stream. Channelization, introduced predators, pollution, and water withdrawal have subsequently eliminated them from most of the original habitat, and made recolonization of streams difficult. By the time biologists began to study the crustacean, they were only known to occur in nine streams. In 1964, the shrimp were eliminated from Santa Rosa Creek, when the stream was channelized and lined with concrete for flood control purposes. By 1975, shrimp were thought to have disappeared from five more streams, apparently leaving populations only in East Austin and Salmon Creeks in Sonoma County, and Lagunitas Creek in Marin County. The closely related Pasadena Freshwater Shrimp (Syncaris pasadenae), a native to southern California, disappeared forever in the 1930s. Extinction now also threatened the only remaining species in the genus! Recognizing this danger, California freshwater shrimp were listed as endangered by the California Fish & Game Commission in 1980. Fortunately, new populations were discovered in Sonoma Creek in Sonoma County and Huichica Creek in Napa County by 1981. During a subsequent distribution study of the species in the early 1980s, I sampled 146 sites in 53 potential streams, and found the shrimp in six additional streams: Big Austin, Green Valley, Jonive, Yulupa, and Blucher creeks in Sonoma County, and Stemple and Walker creeks in Marin County. However, the populations in many of these streams are small and could disappear even without any additional impacts. For example, only one shrimp was found in Walker Creek, even though several miles of the stream had been waded and sampled with nets. The shrimp were listed by the U.S. Fish & Wildlife Service as endangered in 1988. Since that time, shrimp have been found surviving in the
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Last updated:
May 27, 2008
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