196 
Fishery Bulletin 109(2) 
I 
ences among other parameters, such as oxygen concen- 
tration and turbidity (data not shown), showed similar 
patterns. Because water conditions vary little in the 
region surveyed they are unlikely to explain site-spe- 
cific variability. Other unmeasured variables, however, 
such as substrate composition, sediment contamination, 
or shoreline and land cover characteristics in regions 
adjoining each sample site may potentially explain ad- 
ditional variance in the assemblage. We note, however, 
that spatial autocorrelation was not detected in the data 
set and indicates that spatially structured environmen- 
tal variables, such as those that covary with coastal 
urbanization, are unlikely to explain much additional 
variation at least at the spatial scales embraced by our 
survey (Borcard et al., 1992). 
Our research provides the first published assessment 
of seasonal variability in assemblage structure across 
multiple depths in the Puget Sound demersal fish as- 
semblage and offers insight into general features of 
deep fjord systems. We found strong structuring of the 
assemblage by depth and smaller, although important, 
differences across seasons. These shifts were manifest 
in simple assemblage metrics and in multivariate taxon- 
based and size-based analyses. The identification of 
these patterns, in turn, identifies priorities for future 
investigators that will further our understanding of the 
demersal assemblage and the forces that act to shape 
it. Notably, we identified species that may seasonally 
modify the Puget Sound food web in significant ways 
(e.g., spiny dogfish) and we confirmed the findings of 
other researchers who have identified spotted ratfish 
as one of the most abundant fishes in the Puget Sound 
region (Quinnel and Schmitt 3 ). Remarkably, research 
directed toward uncovering the life history and ecol- 
ogy of spotted ratfish has been limited (but see Quinn 
et al., 1980; Barnett et al. 2009). Furthermore, key 
species in the Puget Sound food web may be those that 
link habitats through movement and foraging activi- 
ties. Understanding diel and seasonal-scale movement 
patterns will greatly improve our understanding of the 
Puget Sound fish assemblage. 
Acknowledgments 
Financial support was provided for J. Reum by the 
Vincet Liguori Fellowship and funding for boat time 
was provided by the University of Washington Research 
Royalties Fund. We are grateful to A. Beaubreaux, M. 
Hunsicker, J. Murphy, K. Marshall, M. Anderson, and 
D. English for assistance with field work. Comments 
from M. Hunsicker, C. Harvey, G. Williams, and three 
anonymous reviewers greatly improved earlier versions 
of this article. 
3 Quinnell, S., and C. Schmitt. 1991. Abundance of Puget 
Sound demersal fishes: 1987 research trawl survey results, 
240 p. Washington State Dept. Fish and Wildlife, Olympia, 
WA. 
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