Ichthyoplankton samples were collected at approximately
2-week intervals, primarily during spring and summer 1999−2004, from two stations located 20 and 30 km from shore near the Columbia River, Oregon. Northern anchovy
(Engraulis mordax) was the most abundant species collected, and was the primary species associated with summer upwelling conditions, but it showed significant interannual and seasonal fluctuations in abundance and occurrence. Other abundant taxa included sanddabs (Citharichthys spp.), English sole (Parophrys vetulus), and blacksmelts (Bathylagidae). Two-way cluster analysis revealed strong species associations based primarily on season (before or
after the spring transition date). Ichthyoplankton
abundances were compared to biological and environmental
data, and egg and larvae abundances were found to be most correlated with sea surface temperature. The Pacific Decadal Oscillation changed sign (from negative to positive) in late 2002 and indicated overall warmer
conditions in the North Pacific Ocean. Climate change is expected to alter ocean upwelling, temperatures, and
Columbia River flows, and consequently fish eggs and larvae distributions and survival. Long-term research is needed to identify how ichthyoplankton and fish recruitment are affected by regional and largescale oceanographic proce
