August 1, 2015.
In 2010 the delta smelt (Hypomesus transpacificus), became protected under the California Endangered Species Act. Endemic to the San Francisco Estuary, their numbers have been declining since the mid 1990s. Many factors have contributed to their low numbers, such as alterations to their habitat, predation, water diversions, and prey abundance. Several invasive species of jellyfish may be sources of competition for the native delta smelt because they both eat the same food source of copepods. From July 2010 to December 2012, samples of zooplankton, including jellyfish, were taken from 9 different stations in the high and low salinity areas of the San Francisco Estuary. Samples were preserved and then processed to identify jellyfish and to quantify their abundance. The five most abundant species include four hydromedusae (Blackfordia virginica, Maeotis marginata, Moerisia lyonsi, and Polyorchis penicillatus) and one ctenophore (Pleurobrachia bachei). Abundances ranged from 0 to 6 jellyfish m-3. It is important to identify and quantify the jellyfish in the San Francisco Estuary to better understand the complex food web of the delta smelt.
Romberg Tiburon Center for Environmental Studies (RTC)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).