Biological and physical ocean indicators predict the success of an invasive crab, Carcinus maenas, in the northern California Current

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  • An introduced population of European green crabs Carcinus maenas was established in San Francisco Bay (California, USA) prior to 1989. Subsequently, their larvae were likely carried northward into the embayments of Oregon, Washington (USA), and British Columbia (Canada) by the unusually strong Davidson Current during the winter of the El Niño of 1997-1998. Since this colonizing event, green crabs in Oregon and Washington have persisted at low densities. In this study, we show that after the arrival of the strong founding year-class of 1998, significant recruitment to the Oregon and Washington populations has occurred, but only in 2003, 2005, 2006 and 2010. Warm winter water temperatures, high positive values of the Pacific Decadal Oscillation (PDO) and Multivariate ENSO (El Niño Southern Oscillation) indices in March, weak southward shelf currents in March and April, a late biological spring transition, and high abundance of subtropical copepods are all strongly correlated with strong year-classes. We hypothesize that northward transport of larvae from California by coastal currents during warm winters is the mechanism by which the larvae are delivered to the Pacific Northwest. Among the best indicators of northward flow (and green crab recruitment) were the date of ‘biological spring transition’, the sign of the PDO, and the biomass of southern copepod species, which indicate (1) stronger northward flow of coastal waters during winters, (2) relatively warm winters (sea surface temperature >10°C), which enable larvae to complete their development in the near-shore, and (3) coastal circulation patterns that may keep larvae close to shore, where they can be carried by tidal currents into estuaries to settle.
  • Keywords: El Niño, California current system, Plankton community structure, Year-class strength, Alongshore currents, Recruitment, Pacific Decadal Oscillation, European green crab
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  • Yamada, S. B., Peterson, W., & Kosro, P. M. (2015). Biological and physical ocean indicators predict the success of an invasive crab, Carcinus maenas, in the northern California Current. Marine Ecolology Progress Series, 537, 175-189. doi:10.3354/meps11431
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  • 537
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  • This research was supported, in part, by the Pacific Marine Fisheries Commission (S.B.Y.) and, through the U.S. Global Ocean Ecosystem Dynamics program, by the National Science Foundation and National Oceanic and Atmospheric Administration (PMK, WP); this is U.S. GLOBEC contribution #752. W.T.P. also received support from the NOAA/NMFS Stock Assessment Improvement Program and NOAA/NMFS Fisheries and the Environment Program. P.M.K. also received funding from NANOOS/IOO



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