Linking ocean conditions to year class strength of the invasive European green crab, Carcinus maenas

Once a non-native species arrives and survives in an area, its long-term persistence depends on its recruitment success. If conditions are not favorable for recruitment it will ultimately disappear. The European green crab (Carcinus maenas) has a 6 year life span and has persisted at low densities in Oregon and Washington coastal estuaries for the past 12 years. We show here that after the arrival of the strong founding year class of 1998, significant self-recruitment to the Oregon and Washington populations occurred only in 2003, 2005 and 2006. Warm winter water temperatures, high Pacific Decadal Oscillation and Multivariate ENSO (El Nio Southern Oscillation) Indices in March, late spring transitions and weak southward shelf currents in March and April are all correlated with the these strong year classes. Cold winter water temperatures, low Pacific Decadal Oscillation Indices, early spring transitions and strong southward (and offshore) currents in March and April are linked to year class failure. Right now, green crabs are still too rare to exert a measurable effect on the native benthic community and on shellfish culture in Oregon and Washington. However, if their numbers were to increase, we would be able to predict the arrival of strong year classes from ocean conditions and alert managers and shellfish growers of possible increases in predation pressure from this invader.