Vernal Pools

Fairy Shrimp FAQ's

  • California hosts 23 different species of fairy shrimp—approximately 47% of the species diversity in all of North America. Of the 23 California species, 9 are found nowhere else. Of the six species of federally endangered fairy shrimp, San Diego fairy shrimp (Branchinecta sandiegonensis) and Riverside fairy shrimp (Streptocephalus woottoni) are found in Region 5 (which includes San Diego, and Los Angeles counties).

  • Fairy shrimp are crustaceans, relatives of lobsters and crabs.  Fairy shrimp are typically quite small 0.5 inch-0.75 inch, while the occasional species like the giant fairy shrimp grow as large as 6 inches.

  • Fairy shrimp swim on their back using their phyllopods (feet) for locomotion, which also double as gills. Branchiopods also use these feet to non-selectively filter feed bacterial, plant, animal, detrital, and other particulates.

  • Fairy Shrimp are highly specialized species specializing in short life cycles necessary to inhabit the temporary pools of water where they are found. In southern California, these pools of water persist for short periods of time before drying up. Accordingly, shrimp fill a tough niche to eke out a living; they hatch, grow, mature, reproduce and die within a matter of a few weeks to several months.

  • Shrimp hatch from cysts which are akin to dry eggs. Females produced a shelled embryo that remain in a state of suspended development. The Cyst's hard shells and suspended development allow the embryos to persist in extreme (e.g. hot, cold, and dry) conditions remaining viable in excess of 25 years. Each winter, rain, runoff, and snowmelt fill seasonal pools triggering the fairy shrimp to hatch.

  • Once hatched, fairy shrimp race to grow, mature, and reproduce before their temporary pool of water dries and desiccates. This life cycle repeats as with adequate rainfall.

  • Fairy shrimp are an important, even if transitory, link in the food chain and serve as a food source for wading and diving birds, as well as aquatic insects. Fairy shrimp also help to keep the pools they inhabit clean by filtering algae, bacteria, protozoa and other microorganisms from the water.

  • The primary threat to fairy shrimp in southern California is habitat loss resulting from grazing, agriculture, and developments. According to the Federal Registrar 90-98% of Orange and San Diego Counties' vernal pools have been lost. There is growing concern over the hybridization of fairy shrimp amongst typically isolated pools/populations. Poor pool management practices, cross-contamination, and natural processes all may play a role in the hybridization of endangered fairy shrimp. 

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