Between a rock and a hard place: the ecology of ovigerous green crab,Carcinus maenas (L.), with emphasis on implications for monitoring andcontrol efforts

摘要

Efforts to eradicate nonindigenous species or control their spread may fail if management plans do not specifically focus on critical or susceptible life history stages of the target organism. The case of European green crab, Carcinus maenas, in the northeastern Pacific provides one such example. Control strategies often rely on baited traps that primarily capture male crabs because ovigerous (egg-bearing) females are less mobile and unresponsive to bait. Yet removing males is of little consequence in limiting populations; one male can mate with multiple females within a season, and sperm storage by the latter may allow them to fertilize many broods from a single encounter. The targeted removal of ovigerous C. maenas may be an effective method for reducing propagule pressure, but the lack of information regarding their habitat use and behavior has hindered efforts. We conducted intertidal surveys in Tomales Bay, California, in May/June 2001, and experiments were undertaken at Bodega Marine Laboratory, Bodega Bay, California, to investigate substrate preference and habitat competition with native brown rock crab, Cancer antennarius. Survey observations suggest that aggregations of ovigerous C. maenas occur under boulders or other structure at +0.11 to +0.41 m MLLW. These crabs also preferentially bury in medium/coarse sand under field and laboratory conditions. Results of a competition experiment and nighttime video observations indicate that C. antennarius may affect the distribution and habitat usen of ovigerous C. maenas in some areas. Implications for monitoring and control efforts are discussed as well as recommendations for future work.