444 
Fishery Bulletin 1 10(4) 
A 
April 
May 
June 
B 
100 
90 
80 
70 
60 
50 
40 
30 -I 
20 
10 
0 
April 
Time period 
May 
June 
SH 
78-80 ' 07-10 
78-80 ' 07-10 
Time period 
1969 78-80 ' 07-10 
□ 
□ 
S3 
□ 
Juvenile salmon 
American shad 
Northern anchovy 
Pacific herring 
Surf smelt 
Shiner perch 
Stickleback 
| 3 Subyearling Chinook 
[3 Yearling Chinook 
U Coho 
£3 Steelhead 
1 31 Sockeye 
ITTI Chum 
Figure 8 
Comparison of purse seine catch data, summarized by month and time period 
from historical studies (1969, 1978-80) and our recent study (2007-10) of the 
fish assemblage in the lower Columbia River estuary. (A) Relative abundances 
of the dominant fish species — juvenile Pacific salmon (Oncorhynchus sp.; all 
species and age classes combined), American shad ( Alosa sapidissima ), north- 
ern anchovy (Engraulis mordax), Pacific herring ( Clupea pallasii ), surf smelt 
( Hypomesus pretiosus), shiner perch ( Cymatogaster aggregata), and threespine 
stickleback (Gasterosteus aculeatus). (B) Species-and-age composition of juvenile 
salmon, which comprises subyearling and yearling Chinook salmon (Oncorhynchus 
tshawytscha), coho salmon (O. kisutch), steelhead (O. mykiss), sockeye salmon 
(O. nerka), and chum salmon (O. keta). Data sources for other two studies: for 
the year 1969 — Johnsen and Sims, 1973; for the years 1978-80 — Dawley et al. 7 
Johnsen and Sims (1973) did not differentiate between subyearling and yearling 
(age 1) Chinook salmon; therefore, all fish of this species were assigned to the 
subyearling Chinook category. 
April, but our observation may reflect changes in hatch- 
ery practices. 
Recoveries of fish tagged with CWTs and PIT tags 
indicate that individuals originated from all accessible 
portions of the Columbia River, including the lower, 
mid-, and upper Columbia and Snake and Willamette 
rivers (Table 5) — an observation that also was made 
in an earlier study (Dawley et al. 2 ). However, tagging 
effort is not consistent throughout the Columbia River 
(RMIS database; FPC database); therefore, the relative 
number of fish originating from different parts of the 
Columbia River provided in Table 5 reflects both fish 
origins and tagging effort. In the extreme case, we 
recovered steelhead with CWTs from only the upper 
Columbia and Snake rivers because those basins are 
the only areas where steelhead tagged with CWTs are 
released. 
Perhaps most surprising was our estimate that most 
of the juvenile salmon that we caught were of hatchery 
origin (91-99%; Table 4), percentages that are consider- 
ably higher than the hatchery percentages reported for 
adults (34-80%; NRC, 1996; ISAB 1 ). The percentages 
of clipped subyearling (76.0%; Table 4) and yearling 
(86.9%) Chinook salmon we observed were also higher 
than the percentages reported for juvenile subyearling 
and yearling Chinook salmon collected in nearby shal- 
