Steinhorst et al.: Estimates of abundance for the run composition of saimonids 
11 
determining the groups that will have reliable esti- 
mates in complex scenarios. Even at lower fish abun- 
dances, we can define a lenient precision criterion with 
practical value. 
The estimation approach described in this article is 
very flexible and can be customized for many scenarios. 
In this study, we assumed that window counts were 
a census, and stock and age were determined without 
error. In most applications, abundance is determined 
from a sample rather than a census. Further, there is 
uncertainty in the determination of stock and age for 
each fish. Additional uncertainty (e.g., genetic variabil- 
ity or noncensus estimates of total abundance) can be 
incorporated into our framework by adding additional 
bootstrap steps to reflect the source of the additional 
variance (e.g., method 2 in Steinhorst et al., 2010). An- 
other practical issue is that samples for genetic anal- 
ysis can now be processed en masse, but ages must 
be read from scale samples individually; hence, more 
fish can be identified to stock than can be aged. The 
bootstrap routine can be altered such that all genetic 
information is used to estimate stock abundance, and 
age composition is applied within each stock estimate 
(i.e., age composition is conditional on stock). 
The stratified estimator in our study produced un- 
biased estimates, and the parametric bootstrap CIs 
had good coverage and acceptable precision. In com- 
plex scenarios, estimates of abundance of small groups 
will have poor precision and some may be biased, but a 
stratified estimate with a conservative joint Cl can be 
of practical use if the numbers of fish in other groups 
are much larger. The 2-step bootstrap approach is flex- 
ible and can be adapted to incorporate other sources of 
variability or sampling constraints. 
Acknowledgments 
Funding for this project was provided by Bonneville 
Power Administration under project numbers 1990- 
055-00, 1991-073-00, and 2010-026-00. M. Campbell 
reviewed earlier drafts of this article. We gratefully 
acknowledge the thorough critiques given by 3 anony- 
mous reviewers. 
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