August 1, 2015.
Able to tolerate a wide range of habitats, temperatures, and salinities, Carcinus maenas thrives in much of its non-native range, out-competing native crabs for resources while diminishing food supplies for a variety of marine and estuarine organisms. In Seadrift Lagoon, a manmade inlet of Bolinas Lagoon in Marin County, California, green crabs comprise a significant portion of benthic fauna, and trapping efforts began in 2009 to eradicate them. We analyzed several years of trapping data to monitor demographic changes for this closed population, performed larvae and megalopae sampling with pot scrubbers, and counted eggs on ovigerous females captured in Seadrift Lagoon. Data records reveal a consistently decreasing population from 2009 to 2013, likely due to trapping efforts, followed by an enormous spike in 2014 and consequential crash in 2015. Increased proportions of smaller size classes (<32 mm, 32-40 mm) may be associated with preceding years of increased proportions of gravid females. No larvae or megalopae were observed within the 115 samples taken over the course of 4 weeks in July 2015, and egg counts yielded an average of 30,000 eggs per female (average carapace width 49.5 mm). We conclude that larvae may be scarce as a result of predation, intraspecific competition for food or nursery habitats, early- or late-summer settlement, or some combination of these factors.
Marine Biology | Population Biology | Terrestrial and Aquatic Ecology
Andrew L. Chang
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).