Abstract:
The introduced European green crab, Carcinus maenas, poses a potential risk to
the restoration of the native Olympia oyster, Ostrea lurida, in Tomales Bay, California.
The green crab is a voracious predator, and has negatively impacted shellfish in both its
native and invaded environments. The Olympia oyster population in Tomales Bay is low
due to pollution, predation, and past overharvesting. A collaborative restoration project
began in 1999 to try and reinstate the Olympia oyster to Tomales Bay by placing artificial
reefs at several locations in the Bay. I investigated the potential impacts of the European
green crab on the Olympia oyster during July and August 2003. At four field sites in
Tomales Bay, I trapped green crabs at both potential and established oyster reef
restoration areas. I conducted laboratory feeding experiments of C. maenas on O. lurida
to get an idea of whether or not the crabs would consume the oyster, and whether
different sizes of crabs showed a preference for varying sizes of oyster. Initial trapping
results suggest higher green crab population numbers at rocky habitats as opposed to mud
flats. In addition, the trapping data suggest it may be possible to trap out the green crabs
from the reef areas. The feeding experiments indicate that the green crabs do consume
the Olympia oysters, and that the number of oysters consumed decreased as oyster size
increased.
