Distribution and community structure of ichthyoplankton off the coast of Oregon, USA, in 2000 and 2002

The species composition, distribution and concentration of ichthyoplankton off the central Oregon coast in the NE Pacific Ocean were examined during 2000 and 2002 to investigate annual, seasonal, vertical, and cross-shelf variability. Larval concentrations were also analyzed in relation to water temperature and salinity. The 281 samples collected from 5 cruises along a historically sampled transect between April and September in each of the 2 study years yielded 4944 fish larvae comprising 72 taxa in 28 families. The dominant taxa collected were Engraulis mordax, Lyopsetta exilis, Sebastes spp., Stenobrachius leucopsarus and Tarletonbeania crenularis. Total larval concentration increased from 49.3 per 1000 m(3) in 2000 to 72.0 per 1000 m(3) in 2002, with seasonal concentrations highest in August 2000 (90.3 per 1000 m(3)) and April 2002 (151.2 per 1000 m(3)). Relatively few larvae were found at depths > 100 m, while highest larval concentrations generally occurred from 0 to 50 m. However, L. exilis concentrations were highest from 50 to 100 m. Larval diversity and concentration were higher offshore (46 to 84 km) than in coastal areas (9 to 28 km). Highest concentrations were normally found at an intermediate station 65 km off the coast. Species designated as either coastal or offshore species by previous studies were predominantly found in their respective shelf regions. With the exception of L. exilis, larval concentrations were positively correlated with temperature and negatively correlated with salinity (p < 0.0001).