Anomalous Ichthyoplankton Distributions and Concentrations in the Northern California Current during the 2010 El Niño and La Niña Events Associated with Fluctuating Environmental Conditions

In late spring 2010, the northern California Current experienced a transition from El Niño to La Niña conditions resulting in anomalous distributions and concentrations within the ichthyoplankton community. We analyzed larval fish data collected during the four months before and after this transition and compared them to results from three previous regional studies. Concentrations of larvae collected during winter along the central Oregon coast were higher in 2010 than in any other year from 1998-2011. In a second comparison of near-shore larvae collected during six periods (1971-1972, 1978, 1983, 1998, 1999-2002, and 2003-2005) previous to 2010, concentrations of total larvae and most dominant larval taxa were higher during the winter/spring and lower during the summer/fall seasons in 2010 than during similar seasons in any other period. Also, larvae collected from stations 21-102 km offshore along the southern Washington to south-central Oregon coast in May 2010, at the end of the El Niño event, were found in higher concentrations than during any May from 2004-2009 and 2011. Several seasonally-lagged environmental variables (i.e., MEI, NOI, PDO, upwelling, eastward and north-south Ekman transport, Columbia River outflow, and chlorophyll-a) were found to be associated with the anomalous ichthyoplankton concentrations observed in 2010.