Parnel et al.: Effects of oceanic conditions on ichthyoplankton communities in the Columbia River plume 
169 
Table 3 
Average annual 3-m salinity, temperature, and chlorophyll a values at two stations off the Columbia River, Oregon. Also shown 
is average spring (April-June) Columbia River flows and day of the spring transition. The day of the spring transition (when 
upwelling begins) was identified with the methods of Loggerwell et ah, 2003. Only temperature and Columbia River flows were 
found to have significant annual differences (ANOVA, P<0.05). 
Year 
Salinity 
Temperature (°C) 
Chlorophyll a (pg/L) 
Columbia River flows (m 3 /s) 
Day of spring transition 
1999 
28.53 
11.51 
4.81 
9999 
1 Apr 
2000 
29.92 
12.61 
2.34 
8132 
12 Mar 
2001 
29.19 
13.28 
2.66 
4506 
2 Mar 
2002 
27.93 
12.61 
6.12 
8640 
21 Mar 
2003 
26.68 
12.93 
5.61 
8316 
22 Apr 
2004 
27.50 
14.09 
5.07 
6777 
19 Apr 
Table 4 
Results of the multi-response permutation procedure (MRPP) and indicator species analysis (ISA) for annual, seasonal (before 
and after the spring transition [Logerwell et al., 2003]), and station differences in composition of the dominant egg and larval 
ichthyoplankton taxa. Shown are the MRPP A-statistic, overall significance value, and significant pair-wise comparisons that 
emerged. The significant indicator species are listed with the year or season with which each species is associated in parentheses. 
Stage 
Variable 
MRPP 
A-statistic 
P value 
Significant differences 
between levels 
Significant 
indicator species 
Eggs 
Year 
0.1253 
<0.001 
2003 * all years but 2004 
2004 * all years but 2002, 2003 
Pleuronichthys decurrens, 
Trachurus symmetricus 
(2000), Engraulis mordax 
(2003) 
Season 
0.0231 
0.087 
None 
Psetticthys melanostictus, 
Microstomus pacificus 
(downwelling), E. mordax, 
Citharichthys spp. 
(upwelling) 
Station 
0.0019 
0.631 
None 
None 
Larvae 
Year 
0.1027 
0.068 
2003 * 1999 and 2004 
2002 * 2004 
Parophrys vetulus, 
M. pacificus 
(downwelling), 
E. mordax (2004) 
Season 
0.0787 
0.018 
downwelling * upwelling 
E. mordax (upwelling) 
Station 
0.0003 
0.412 
None 
None 
thermore, northern anchovy eggs are positively buoyant 
and appear to concentrate in plume fronts (Morgan et 
ah, 2005), which often occurred in our sampling region. 
The observed annual increase in northern anchovy egg 
densities appear to be strongly linked to the increase 
in the abundance of adult northern anchovy population 
in the study area (Emmett et ah, 2006). Anchovy egg 
densities also may have been influenced by Columbia 
River spring flows. For example, densities of northern 
anchovy egg and larvae were lower in 2001, a drought 
year during which Columbia River flows were very low 
and the plume area was relatively small (Brodeur et 
ah, 2005). However, numbers of northern anchovy eggs 
were also down in 2002, which was not a drought year, 
but was the year that the Pacific Decadal Oscillation 
(PDO) changed from negative to positive (Goericke et 
ah, 2005). 
Richardson (1981) found that the peak of northern 
anchovy spawning in 1975 and 1976 occurred in July, 
whereas we found that the peak of spawning occurred 
in May during five of the six study years. However, this 
difference could have been due to Richardson (1981) 
not sampling in May and June. Brodeur et al. (1985) 
found northern anchovy spawning during April 1983, 
but 1983 was a strong El Nino year and therefore there 
were unusually warm ocean conditions. Jones et al. 
(1990) found northern anchovy eggs and larvae in the 
Columbia River estuary from April to September 1980, 
