Common Name: Unarmored Threespine Stickleback
Scientific Name: Gasterosteus aculeatus williamsoni
Federal Register: 35 FR 16047 (Oct. 13, 1970)
Lt. Robert S. Williamson.
Comments: This little fish (adults are about 1 inch in length) is perhaps the most
familiar of the locally occurring endangered species, probably because it has been on the "protected"
list the longest and because the Santa Clarita Valley is its principal habitat.
The name "williamsoni" is for the man who first identified the fish as a separate species
Lt. R.S. Williamson of the U.S. Army Corps of Topographical Engineers in the 1850s under Secretary of War Jefferson Davis.
Like their armored brethren, which have a plating of hard scales on their sides,
unarmored stickleback prefer fast-flowing waters and have been observed in the Santa Clara River in locations
where there is water year-round, esp. in an area of Soledad Canyon west of State Route 14, between Canyon Country and Acton; and also in the
San Francisquito Creek. They are also believed to occur at Vandenburg Air Force Base in Santa Barbara County, and possibly in San Diego County.
Stickleback are a dull greenish-gray with a pinkish-silver belly. Males are reddish, or may turn red at breeding time to attract females.
They use plant material to construct small nests in the streams for their eggs and young, secreting a mucousy
substance to glue the nest together. Adults, esp. males, will protect the nest and eggs from predators.
An enemy is the African clawed frog (Xenopus laevis), which is an imported (non-native) species.
Photos courtesy of Dianne Erskine Hellrigel.