by Eric Ettlinger
This post is the sixth in a year-long series celebrating the 40th anniversary of the Endangered Species Act. Read the previous post here.
In our monthly series celebrating the 40th anniversary of the Endangered Species Act, we’ve so far covered the mighty bald eagle, fascinating frogs, and beautiful but exceptionally rare flowering plants—all found on the Mt. Tamalpais Watershed. It now falls on me to introduce the most diminutive and charisma-challenged local endangered species that you will likely never see. Measuring less than 2.5 inches long, with a translucent body and a unicorn-like barb, please give it up for the California freshwater shrimp (Syncaris pacifica)!
These little shrimp (that’s somewhat redundant, isn’t it?) are found in slow water habitats throughout lower Lagunitas Creek, downstream of MMWD’s watershed lands. There they feed on detritus—the bits of organic matter that wash downstream and collect on aquatic plants and roots that extend into the water from bank vegetation. Their translucent bodies and subtle movements make them nearly impossible to be seen by native fish species, but non-native fish such as bass are highly efficient hunters and aren’t as easily fooled. Luckily the shrimp have a last-ditch defense. When eaten, they can jab their sharp spine into the roof of the fish’s mouth and hopefully encourage the fish to spit them out. Shrimp are occasionally found with a broken rostral spine, which may be evidence of a close escape.
About 3,000 species of shrimp exist worldwide, including roughly 650 freshwater species. North America hosts only 17 freshwater species, including the California freshwater shrimp. A sister species, the Pasadena freshwater shrimp, lived in southern California before going extinct in the 1930s. That shrimp was the only other member of the Syncaris genus and the only freshwater shrimp to go extinct in recent times. The closest remaining relatives in North America are two species of cave shrimp in Kentucky and Alabama.
The risk of becoming the next shrimp to go extinct becomes clear when one realizes that the global distribution of Syncaris pacifica is limited to about 20 streams in Marin, Sonoma and Napa Counties, and all but one of these streams (Lagunitas Creek) are on private land. Channelized creeks, banks hardened with riprap, cattle grazing, water diversions, pesticides and non-native fish are all threats to its continued existence. Lagunitas Creek, however, remains a shrimp stronghold, where these threats are greatly reduced. Shrimp habitat is well protected on federal and State Park land, non-native fish are uncommon, and the creek has more water in the summer than it did historically, due to releases of water by MMWD. Surveys in recent years have found above-average numbers of shrimp in Lagunitas Creek. In other creeks, private landowners and community groups are working to protect and restore shrimp habitat. So while very few people are fortunate enough to see one of these unique animals, many people are working for their continued survival.