Scordino et al.: Dietary niche overlap and prey consumption for Eumetopias jubatus and Zalophus californianus 47 
Table 2 (continued) 
Prey group 
Octopuses, unidentified 
Squids, unidentified 
Sand lances: family Ammodytidae 
Pacific sand lance (Ammodytes hexapterus) 
Lampreys: family Petromyzontidae 
Lampreys, unidentified 
Pacific lamprey (Entosphenus tridentatus) 
Mackerels and tunas: family Scombidae 
Pacific chub mackerel (Scomber japonicus) 
Smelts: family Osmeridae 
Smelts, unidentified 
Eulachon (Thaleichthys pacificus) 
Sticklebacks: family Gasterosteidae 
Threespine stickleback (Gasterosteus 
aculeatus) 
Poachers: family Agonidae 
Poachers, unidentified 
Sturgeon poacher (Podothecus 
accipenserinus) 
Sculpins: family Cottidae 
Sculpins, unidentified 
Pacific staghorn sculpin (Leptocottus 
armatus) 
Snailfishes: family Liparidae 
Snailfishes, unidentified 
Hagfishes: family Myxinidae 
Pacific hagfish (Eptatretus stoutii) 
Gunnels: family Pholidae 
Gunnels, unidentified 
Eelpouts: family Zoarcidae 
Eelpouts, unidentified 
Jacks: family Carangidae 
Jack mackerel (Trachurus symmetricus) 
Frogs and salamanders, class Amphibia 
Frogs and salamanders, unidentified 
Wolffishes: family Anarhichadidae 
Wolf-eel (Anarrhichthys ocellatus) 
Salmonidae (13.5%), Merlucciidae (11.3%), Sebasti- 
dae (9.3%), Squalidae (7.8%), and Engraulidae (5.0%) 
(Table 4). 
For California sea lions, diet diversity was similar in 
spring and summer, but the diet was less diverse in fall 
(Table 3). There were large differences in the SSFO of 
some prey families between seasons. The 3 most dominant 
families of prey made up 58.6% of the diet of California sea 
lions in spring, 55.3% of the diet in summer, and 77.7% of 
the diet in fall. Consumption of Sebastidae dramatically 
declined in the fall to an SSFO of 2.0% from 20.5% and 
22.8% in the spring and summer, respectively. Cephalop- 
oda composed a primary prey group during spring (6.3%) 
and summer (8.4%) but were only 1.6% of the diet in fall. 
During the fall, 47.4% of the California sea lion diet was 
composed of Clupeidae, compared with 24.6% in spring 
and 20.5% in summer. Higher consumption of Clupeidae 
Spring Summer 
in the fall appears to be due to the consumption of Pacific 
sardine, which had an SSFO of 11.4% in the fall and was 
not present in the spring or summer. 
For yearly comparisons of the diet of California sea lions, 
we used only data collected during the fall because sam- 
ples were not collected in all seasons of each study year 
(Suppl. Table 6) (online only). Prey diversity was similar 
between years during the fall (Table 3). The SSFO of prey 
taxa varied between years. Consumption of Pacific hake 
declined from 23.4% and 18.0% of the diet in 2010 and 
2011, respectively, to 4.6% in 2012, and consumption of 
northern anchovy declined from 10.7% and 7.1% of the diet 
in 2010 and 2011 to 2.2% in 2012. As the SSFO of Pacific 
hake and northern anchovy declined, California sea lions 
ate more Clupeidae (41.7% in 2010 versus 51.0% in 2012), 
such as Pacific sardine and American shad (Alosa sapidis- 
sima). Consumption by California sea lions of Salmonidae 
