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Fishery Bulletin 106(2) 
were calculated by using the normalized Euclidean dis- 
tance on fourth-root transformed data. Environmental 
variables in the analysis included sea surface tempera- 
ture, salinity, chlorophyll a at 3 m, the settled volume 
of zooplankton, and Columbia River flow (measured by 
U.S. Geological Survey at Beaver, OR). 
A paired f-test was used to determine if environ- 
mental conditions and zooplankton volumes at the two 
stations were significantly different. To account for 
interannual and seasonal variations in sampling, only 
those samples collected within a similar season were 
considered. All statistical tests were considered signifi- 
cant at the a <0.05 level. 
Results 
In total, 85 samples were collected during this study, 
comprising a total of 155,302 fish eggs and 3565 fish 
100 
100 
1999 
2000 
2001 2002 
Year 
2003 
2004 
Figure 2 
The top five egg (A) and larval (B) taxa collected at two stations 
off the mouth of the Columbia River, Oregon, as a percentage 
of total catch for each year from 1999 through 2004. 
larvae, representing 34 taxa and 17 families. However, 
a majority (n- 78) of these samples were taken from 
April to August and formed the primary data set that 
was analyzed (Table 2). The family Pleuronectidae had 
the greatest number of taxa (9), followed by the family 
Cottidae (6). The actual number of fish species collected 
was probably higher than the number we report because 
some eggs and larvae could be identified only to genus 
or family, namely eggs and and larvae of Osmeridae, 
Bathylagidae, Citharichthys spp., Sebastes spp., and 
Sebastolobus spp. Nine taxa were found only once during 
our sampling. 
The most abundant fish eggs were those of northern 
anchovy, sanddab ( Citharichthys spp.), blacksmelt ( Bath - 
ylagus spp.), jack mackerel (Trachurus symmetricus), 
and Pleuronectidae, in descending order of abundance 
(Fig. 2A). The most abundant larvae, in descending 
order, were northern anchovy, English sole ( Paroph - 
rys vetulus), sand sole ( Psettichthys melanostictus), rex 
sole ( Glyptocephalus zachirus), and Pacific tomcod 
( Microgadus proximus) (Fig. 2B). The unidentified 
Pleuronectidae eggs were of four species (butter 
sole [Isopsetta isolepis], English sole, starry floun- 
der [Platichthys stellatus], and sand sole) which 
cannot be identified to species at early egg stages. 
Unusual egg occurrences included those of Pacific 
viperfish ( Chauliodus macouni ), opah (Lampris 
guttatus ), and jack mackerel. These species are 
considered either offshore (viperfish and opah) or 
southern, warm-water spawners (jack mackerel). 
Jack mackerel eggs were observed in 1999-2002, 
but not in 2003 or 2004 (Fig. 2A). Peak jack mack- 
erel spawning occurred in July 1999 and June 
2000-2002, although some eggs were also found 
from May to September during most years. 
Northern anchovy accounted for 76% of all eggs 
collected, and were found from May through July 
(Fig. 3). Overall, northern anchovy were pres- 
ent in 53 of the total 85 samples collected. Peak 
northern anchovy egg abundance varied interan- 
nually, occurring in June of 1999, 2001, and 2002; 
July of 2000; and in May of 2003. The highest 
annual density of northern anchovy eggs was ob- 
served in 2003, when eggs were almost four times 
as abundant as those observed in 2002 (Fig. 3). 
Northern anchovy eggs dominated the catch in all 
years except 2001, when blacksmelt and sanddab 
contributed about equally to the catch (Fig. 2). 
Northern anchovy larvae were the most abun- 
dant fish larvae, and represented 68% of all larvae 
collected. In 1999, 2001, and 2002, peak numbers 
of these larvae occurred in June, whereas in 2000, 
northern anchovy larval numbers peaked in July. 
In 2003 and 2004, northern anchovy larval num- 
bers peaked in May and represented the majority 
of the larval fish catch (Fig. 2B). 
Nine samples contained only one egg or larval 
fish species (and therefore a diversity and even- 
ness of zero), and three samples contained no ich- 
thyoplankton. Overall sample diversity ranged 
