Reum and Essington: Season- and depth-dependent variability of a demersal fish assemblage in a fjord estuary 
193 
October 20 m 
Spiny dogfish 
( Squaius acanthias) 
g Spotted ratfish 
(Hydrolag us colliel) 
□ Flatfish 
■ Other 
0.4 
0.3 
0.2 
0.1 
0 
July 20 m 
bd 
n 
0.4 1 
n 
October 40 m 
i 
1 1 j — i — j — i 
March 40 m 
n 
Un 
7 9 11 
I October 80 m 
11 
0.4 
0.31 
0.2 
0.1 
0 
0.4 
0.3 
5 7 9 11 
July 40 m 
y 
i=n 
— — i 
9 11 
1 0 . 2 - 
, , , ov 
"SS 
— i n 
July 80 m 
1 3 5 7 9 11 
October 1 60 m 
1 3 5 7 9 11 
July 1 60 m 
0 -I — 1 — ' i F 3 
1 3 5 7 9 11 
Log 2 body mass (g) 
Figure 5 
Average normalized biomass spectra of the demersal fish assemblage from the Central Basin 
of Puget Sound sampled with bottom trawl at different depths from October 2004 and March 
and July 2005. 
substantially across depths and among seasons, but 
was unusual in that chondrichthyans (spotted ratfish 
and spiny dogfish) made up a majority of the fish bio- 
mass. Fish assemblages in estuaries on the outer coast 
of Washington, Oregon, and California are dominated 
by teleosts (e.g., Armor and Herrgesell, 1985; Bottom 
and Jones, 1990; De Ben et al., 1990), and this finding 
shows that demersal fish assemblages in Puget Sound 
differ fundamentally from shallower estuarine systems. 
Total assemblage biomass at depths of 80 and 160 m 
principally comprised spotted ratfish year round and 
spiny dogfish seasonally. Deepwater habitat is wide- 
spread in the Central Basin (average depth: 120 m; 
Burns, 1985), making these two species the dominant 
species, in biomass, in the area surveyed. An abundance 
of spotted ratfish has also been noted in deep waters 
immediately adjoining Puget Sound (Palsson et al. 2 ), 
but what remains poorly understood is whether spotted 
ratfish are common in northeastern Pacific fjords or 
whether they are superabundant only in Puget Sound. 
Spotted ratfish are primarily benthic feeders, feeding 
on polychaetes and bivalves and occasionally on small 
fishes (Quinn et al., 1980), which indicates that they 
potentially are competitors to benthic feeding flatfish- 
es (Reum and Essington, 2008). In addition, they are 
preyed upon by large elasmobranchs (e.g., sixgill sharks 
[Hexanchus griseus], spiny dogfish). There is presently 
insufficient information to evaluate whether the high 
abundance of spotted ratfish is a secondary effect of 
shifts in food web structure, or whether other envi- 
2 Palsson, W. A., S. Hoffmann, P. Clarke, and J. Beam. 
2003. Results from the 2001 transboundary trawl survey 
of the southern Strait of Georgia, San Juan Archipelago 
and adjacent waters, 117 p. Washington State Dept. Fish 
and Wildlife, Olympia, WA. 
