User:Vonkeyserlingk/Syncaris pacifica

Syncaris pacifica 's range has changed significantly over geologic time. The distribution of all Atyid shrimp is disjointed much like that of Syncaris; Hedgpeth (1968) suggests that this pattern is a result of a seafaring species turned freshwater in conjunction with rising sea level. California's river systems also may have changed from tectonic effects, and produced the unusual arrangement of S. pacifica-inhabited streams in separate but nearby watersheds, particularly the aberrant appearance in the Napa River.

According to Martin, Saiki, and Fong (2004), within a given stream, S. pacifica strongly prefers glide habitat (areas with moderate flow), and to some extent pools, which are deep with low flow. In a survey they were almost never captured in high-flow riffle areas of Lagunitas or Olema Creeks.

Martin and Wicksten (2004) note the habitat features that control shrimp populations: first, they do not tolerate even slight brackishness. They prefer glide and pool areas with overhanging banks. Never have they been found above 380 feet of elevation. They are known from small streams in just three counties of Northern California.