168 
Fishery Bulletin 106(2) 
Larvae 
Matrix coding 
o 
L_ 
Information remaining (%) 
25 50 75 
I I 1 1 1 
100 
A 
B 
C 
1 -5-99 
■ ■ ■□□□□□[ 
4-30-00 
]□□■□□□[ 
5-21-03 
mum 
4-24-04 
■ ■■ 
5-1-99 
4-24-03 
■ ■ ■ 
2-13-01 
z 
5-8-01 
■ 
5-5-99 
■■■ 
7-1 0-02 
a 
12-6-99 
■ 
5-1 1 -00 
■ 
7-11-01 
□□□■□□□□□□□a 
7-31-01 
□□□■: : ! 1! )□□□□ 
7-17-03 
m m 
3-11-99 
■■ m 
5-28-99 
■ * 
3-21-00 
7-11-00 
■ ■ 
4-14-99 
■ !□■□■■■□ 
5-29-01 
]□■□□□□□ 
6-3-03 
■1 • ■ 
7-23-02 
S 
6-25-03 
■ 
7-9-03 
■ 
6-26-99 
m :jb 
6-27-02 
■ 
5-9-04 
■ 
5-4-03 
■ m 
6-14-03 
m mum 
5-19-04 
9 SSI 
6-8-01 
6-15-02 
□□□■□[ 
5-13-03 
■ ■□□□□□ 
6-18-01 
■ B B ■ 
5-30-04 
BB 
6-14-04 
■ m 
6-24-04 
m m 
Figure 5 
Two-way cluster analysis of larval densities by sampling date. The taxa 
clusters are oriented vertically at the top of the figure and sampling dates 
are oriented horizontally at the left side of the figure. The dashed lines 
delineate sampling dates that contained similar assemblages of larvae. 
The color of the boxes denotes relative abundance of each taxon during 
each sampling period as shown in the matrix coding legend. The taxa 
names are abbreviated as: A. hexa. ( Ammodytes hexapterus), G. zach. 
(Glyptocephalus zachirus), P. decu. (Pleuronichtliys decurrens), E. mord. 
( Engraulis rrwrdax), Seb. spp. ( Sebastes spp.), M. pad. ( Microstomus paci- 
ficus), P. mela. ( Psetticthys melanostictus ) , P. vetu. ( Parophrys vetulus), I. 
isol. ( Isopsetta isolepis), M. prox. (Microgadus proximus), Pleuron. (Pleu- 
ronectidae), and L. exil. ( Lyopsetta exilis ). “Information remaining” is a 
scaled measure of the amount of information that is left after stations 
are grouped.” 
larval taxa did not differ between the 
two stations, and no indicator species 
were identified for either station. Year 
of sampling was a significant factor for 
eggs; 2003 and 2004 showed a differ- 
ent composition from most other years. 
However, eggs of only 3 of the 12 spe- 
cies (curlfin sole and jack mackerel for 
2000; northern anchovy for 2003) were 
determined to be useful indicator spe- 
cies. Season was not a significant fac- 
tor overall for eggs, or for the two taxa 
considered indicators of downwelling 
and upwelling conditions. For larvae, 
year was a marginally insignificant 
factor overall, although there were 
pairs of years that were significantly 
different. Season was a significant fac- 
tor for larvae: Dover sole and English 
sole larvae were indicative of winter 
downwelling, and northern anchovy 
were indicative of summer upwelling 
seasons. Station was not a significant 
factor for eggs or larvae. 
Discussion 
The timing of upwelling (spring transi- 
tion), and its associated ocean tempera- 
tures, appears to be very important in 
determining the structure of the ich- 
thyofaunal community off the Colum- 
bia River and probably within the 
California Current. Upwelling is what 
brings nitrates into the Columbia River 
plume (Lohan and Bruland, 2006) and 
the California Current and ultimately 
determines primary and probably sec- 
ondary production (Hickey and Banas, 
2003). As such, it is not surprising that 
fishes within this region have evolved 
life histories adapted to its presence 
(Bowen and Grant, 1997; Ware and 
Thomson, 1991). However, although 
upwelling drives the nutrient enrich- 
ment processes it also can disrupt the 
abilities of larval coastal fishes to suc- 
cessfully recruit if they are unable to 
take advantage of transport and reten- 
tion processes (Bakun, 1996). 
Several factors account for the high 
abundance of northern anchovy eggs 
and larvae captured during our study. 
The Columbia River plume is an impor- 
tant spawning habitat for northern an- 
chovy (Richardson, 1981; Emmett et al., 
1997) and most samples were collected 
during the typical northern anchovy 
spawning season (May- August). Fur- 
