Bromaghin et al: Diets of Phoca vitulma in the Salish Sea revealed by analysis of fatty acid signatures 
17 
Table 2 
The number of prey animals from which fatty acid signature data were obtained (n) and the prey class (class) into which 
each prey type was assigned after evaluation of discriminant analysis and mean fat mass in our investigation of the diet 
composition of harbor seals ( Phoca vitulina ) in the Salish Sea through quantitative fatty acid signature analysis. Prey 
classes are defined as B&YR (Black [ Sebastes melanops] and Yellowtail [S. flavidus 1 Rockfish), CR (Copper Rockfish [S. 
caurinus}), PSR (Puget Sound Rockfish IS. emphaeus ]), Chin (mature Chinook Salmon \Oncorhynchus tshawytscha ]), Chum 
(mature Chum Salmon |0. keta\), Coho (mature Coho Salmon [O. kisutch]), Sock (mature Sockeye salmon [O. nerka ]), Pink 
(mature pink salmon \0. gorbuscha}), Sal-M (medium-sized Chinook and Coho Salmon), Sal-S (small Chinook, Chum, Sock- 
eye, and Pink Salmon), Pol (Walleye Pollock [ Theragra chalcogramma ]), Her (Pacific Herring [ Clupea pallasii } at least 2 
years old), YH&SL (Pacific Herring less than 2 years old and Pacific Sand Lance [ Ammodytes hexapterus ]), NA (Northern 
Anchovy [ Engraulis mordax]), SP (Shiner Perch I Cymatogaster aggregata ]), PM (Plainfin Midshipman [Porichthys notatus 1), 
SD (Spiny Dogfish [Squalus acanthias ]), OIS (Opalescent Inshore Squid [Loligo opalescens]), G&S&F (Kelp Greenling [ Hexa - 
grammos decagrammus ], Pacific Staghorn Sculpin [ Leptocottus armatus], and Starry Flounder [ Platichthys stellatus 1). For 
each prey type, the sample size in), mean (mean), and standard deviation (SD) of total mass, percent fat composition, and 
total fat mass are shown. Mass data were not available for mature Chinook, Sockeye, or Pink Salmon, and an approximate 
mean mass was used for the computation of fat mass. 
Mass (g) Percent fat Fat mass (g) 
Prey type 
n 
Class 
n 
Mean 
SD 
n 
Mean 
SD 
n 
Mean 
SD 
Black Rockfish 
5 
B&YR 
5 
293.8 
48.3 
5 
6.5% 
0.4% 
5 
19.3 
4.0 
Yellowtail Rockfish 
5 
B&YR 
5 
152.8 
28.2 
5 
5.7% 
1.5% 
5 
8.8 
2.6 
Copper Rockfish 
12 
CR 
12 
201.3 
195.7 
12 
2.4% 
0.4% 
12 
4.7 
4.5 
Puget Sound Rockfish 
14 
PSR 
14 
53.9 
8.9 
5 
2.2% 
0.3% 
5 
1.1 
0.4 
Chinook, mature 
10 
Chin 
0 
10000.0 
NA 
10 
12.2% 
2.3% 
10 
1218.8 
233.3 
Chum, mature 
10 
Chum 
10 
4955.9 
784.6 
10 
15.1% 
7.8% 
10 
789.7 
455.6 
Coho, mature 
10 
Coho 
10 
3765.4 
660.8 
10 
5.5% 
2.8% 
10 
208.2 
125.0 
Sockeye, mature 
10 
Sock 
0 
2500.0 
NA 
10 
12.4% 
1.8% 
10 
309.4 
45.4 
Pink, mature 
10 
Pink 
0 
2000.0 
NA 
10 
5.3% 
2.1% 
10 
105.6 
43.0 
Chinook, medium 
5 
Sal-M 
5 
133.5 
70.3 
5 
3.0% 
1.3% 
5 
4.8 
3.1 
Coho, medium 
4 
Sal-M 
4 
193.0 
28.6 
4 
2.9% 
0.5% 
4 
5.7 
1.7 
Chinook, small 
11 
Sal-S 
12 
20.9 
8.0 
12 
1.3% 
0.3% 
12 
0.3 
0.2 
Chum, small 
12 
Sal-S 
12 
62.8 
24.6 
12 
2.3% 
1.1% 
12 
1.6 
1.5 
Sockeye, small 
12 
Sal-S 
12 
15.5 
2.5 
12 
1.5% 
0.2% 
12 
0.2 
0.1 
Pink, small 
12 
Sal-S 
12 
47.2 
13.6 
12 
2.4% 
0.8% 
12 
1.2 
0.7 
Pollock 
13 
Pol 
13 
29.4 
78.6 
13 
1.8% 
0.4% 
13 
0.5 
1.2 
Pacific Herring >2 yr 
12 
Her 
12 
37.5 
4.2 
12 
11.7% 
3.4% 
12 
4.4 
1.6 
Pacific Herring <2 yr 
12 
YH&SL 
12 
5.8 
0.8 
12 
3.5% 
1.3% 
12 
0.2 
0.1 
Pacific Sand Lance 
12 
YH&SL 
12 
1.9 
0.3 
12 
3.3% 
0.8% 
12 
0.1 
0.0 
Northern Anchovy 
11 
NA 
11 
18.8 
1.7 
11 
12.2% 
3.4% 
11 
2.3 
0.7 
Shiner Perch 
12 
SP 
12 
21.0 
5.8 
12 
6.9% 
2.4% 
12 
1.5 
1.0 
Plainfin Midshipman 
9 
PM 
9 
61.7 
13.4 
9 
3.4% 
0.7% 
9 
2.1 
0.6 
Spiny Dogfish 
4 
SD 
4 
1712.5 
383.8 
4 
9.0% 
3.6% 
4 
160.5 
83.5 
Opalescent Inshore Squid 
12 
OIS 
12 
7.1 
1.9 
12 
3.0% 
0.4% 
12 
0.2 
0.1 
Kelp Greenling 
7 
G&S&F 
7 
179.7 
396.3 
7 
1.5% 
0.4% 
7 
3.0 
6.8 
Pacific Staghorn Sculpin 
12 
G&S&F 
12 
21.0 
10.1 
11 
1.5% 
0.6% 
11 
3.4 
5.7 
Starry Flounder 
11 
G&S&F 
11 
220.2 
410.1 
11 
1.5% 
0.6% 
11 
3.4 
5.7 
with a scan range of 50-400 mass-to-charge ratios 
(m/z). Additionally, a National Institute of Standards 
and Technology 1946 international standard was used 
to externally verify the method and the quality of 
recoveries. 
The ASET Laboratory implements several protocols 
to improve data quality that are not routinely imple- 
mented in analyses of fatty acid data. Rather than 
normalize the peak data of each sample to C18:0, the 
laboratory adds an internal standard to all samples, 
method blanks, and CCVs. This protocol is beneficial 
because it provides a data point of known quantity to 
each resulting set, including blanks, allowing the sig- 
nificance of low-recovery peak data to be verified. In ad- 
dition, because normalization to a recovered compound 
incorrectly entails the assumption that all compounds 
respond equally in the FID, use of an internal stan- 
dard avoids errors that might otherwise result from 
that assumption (Dodds et al., 2005). The laboratory 
also verifies the identity of each peak by using a GC 
mass spectrometer (GC-MS) — verification that is nec- 
essary to eliminate misclassification of non-fatty acid 
