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Fishery Bulletin 109(2) 
CCA1 (10.9%) 
Figure 6 
Partial canonical correspondence analysis (CCA) tri-plots of biomass spectra of fall+summer 
and all seasons analyses in which depth is the constraining variable for (A) and (B), respec- 
tively. For all seasons, only depth was significantly related to variation in the biomass spectra 
(C). In the tri-plots, the site centroids coded for each constraining factor are indicated by 
triangles. The proximity of factor centroids in ordination space to one another corresponds 
to their respective similarity in distribution of biomass across body size classes. Body size 
classes are indicated by circles. Those that have strong loadings (large eigenvectors) are 
distant from the tri-plot origin and contribute the most to differentiating factor centroids that 
separate along the same axis. The eigenvalue or variance associated with each axis is indicated 
within parentheses. In cases were the constraining factor consisted of only two groups, as in 
(B) and (C), only one CCA axis was generated. To aid interpretation two-dimensional plots 
were generated by plotting the CCA (*-axis) against the residual axis (y-axis) derived from 
standard correspondence analysis (CA) performed on the remaining community variance. 
ron mental features of Puget Sound promote their high 
abundance. Historical abundance records of spotted 
ratfish in Puget Sound are available in agency and proj- 
ect reports and indicate that they have been a common 
component of the food web at least since the 1930s, but 
it is difficult to extract trends from these data because 
of the lack of standardization of sample sites and gears. 
Future comparisons with less impacted fjords may of- 
fer insight into whether cartilaginous species naturally 
dominate in these systems or do so only under condi- 
tions related to human-caused ecosystem degradation. 
Despite our poor understanding of long-term changes in 
the Puget Sound fish community, the high abundance 
of ratfish in the area surveyed indicate that they likely 
constitute a significant node in the Puget Sound food 
web and are therefore deserving of further study. 
Spiny dogfish was the most abundant demersal pisci- 
vore and may have a particularly important influence 
on assemblage structure in Puget Sound and other 
coastal ecosystems. Spiny dogfish have a diverse diet, 
feeding on Pacific herring, flatfish, spotted ratfish, sal- 
monids, as wells as a wide range of benthic and pelagic 
invertebrates (Reum and Essington, 2008; Beamish 
and Sweeting, 2009). Large mobile predators such as 
spiny dogfish play an important role by linking differ- 
ent communities through predation and may stabilize 
