Jacobson et at: Use of parasites to clarify migration of Sardinops sagax 
201 
parasites from 59.3% of the Pacific sardine sampled. The 
prevalence of infection (percentage of samples infected) 
of any parasite taxa ranged from less than 1.0% to 
48.4%, and mean intensities of infection ranged from 1.0 
to 7.0 individual parasites of a taxon per infected fish 
(Table 3). 
The most abundant parasite (greatest prevalence and 
intensity) recovered from the Pacific sardine from any 
region was the trematode Lecithaster gibbosus. Its prev¬ 
alence was highest in Pacific sardine caught off British 
Columbia at 48.4% infected. The highest intensity of 
L. gibbosus was 51 individual parasites in a single Pacific 
sardine caught off British Columbia. Although abundant 
in the north, this parasite was not recovered from any 
Pacific sardine caught off Central or Southern Califor¬ 
nia. Another commonly recovered trematode, Myosac- 
cium ecaude, was found at a high prevalence of 41.7% off 
Southern California, as well as at relatively high preva¬ 
lences off Central and Northern California (29.8% and 
28.8%, respectively). This trematode was also recovered 
in the region off Washington and Oregon and off Brit¬ 
ish Columbia but at prevalences of only 8.1% and 5.0%, 
respectively. 
Nematodes from 2 genera, Hysterothylacium sp. and 
Anisakis spp., were also recovered at relatively high 
prevalences (but low intensities) throughout the study 
area (Table 3). Hysterothylacium sp. was recovered 
in highest prevalence (31.5%) in Southern California. 
Anisakis spp. were recovered in highest prevalence off 
British Columbia and in the region off Washington and 
Oregon (25.1% and 24.2%, respectively), but mean inten¬ 
sity was slightly higher for Anisakis spp. in Southern 
California. 
Northern anchovy: parasite taxa recovered 
and distribution patterns 
A total of 7 parasite taxa were recovered from the north¬ 
ern anchovy (Table 4). Parasites were recovered from 60% 
of the northern anchovy caught off Grays Harbor, Wash¬ 
ington, 21% of fish caught off Willapa Bay, Washington, 
and 69% of fish caught off Port Hueneme, California. 
Mean intensities of all parasite taxa were low, ranging 
from 1.0 to 2.0 individual parasites per infected anchovy. 
Although the nematodes Anisakis spp. and Hysterothyla¬ 
cium sp. were recovered from northern anchovy from all 
3 locations, the parasite communities were significantly dif¬ 
ferent (ANOSIM: global 72=0.88, P<0.01). The trematode 
Parahemiurus merus was also found in all locations but at 
higher prevalence off Southern California at 33% infected, 
compared with 5% and 2% in both northern groups. An 
unidentified trematode belonging to the Didymozoidae 
was recovered exclusively from northern anchovy collected 
off Southern California at a prevalence of 41%. In contrast, 
the trematode L. gibbosus was recovered exclusively, and 
at a high prevalence of 45%, from the most northern sam¬ 
ples collected off Grays Harbor. Pairwise ANOSIM showed 
that the parasite communities from the two collections of 
anchovy from different locations off Washington were also 
significantly different (ANOSIM: 72=0.75, P=0.01). 
Multivariate community analyses: parasites of Pacific sardine 
A nonmetric MDS ordination of parasite community data 
averaged by size category and region shows the differ¬ 
ences in parasite communities of all size categories of 
Pacific sardine from British Columbia compared with 
Table 4 
Prevalence (P) and mean intensity (I), with 95% confidence intervals (95% Cl), of parasites recovered 
from northern anchovy (Engraulis mordax ) caught off Washington (WA) in 2007 and Southern Califor¬ 
nia (CA) in 2008. n=sample size. An asterisk (*) denotes that only 2 infected fish were collected. 
Parasite taxa 
Grays Harbor, WA 
in= 20) 
Willapa Bay, WA 
(n= 97) 
Port Hueneme, CA 
(n=51) 
P (%) 
I (95% Cl) 
P(%) 
I (95% Cl) 
P% 
I (95% Cl) 
NEMATODA 
Anisakis spp. 
10.0 
1.5* 
5.2 
1.0 
5.9 
1.0 
Hysterothylacium sp. 
5.0 
1.0 
7.2 
1.3 (0.8-1.8) 
17.6 
1.2 (0.7-1.7) 
Unknown nematode 
0.0 
11.3 
1.3 (0.9-1.7) 
10.0 
1.2 (0.6-1.8) 
TREMATODA 
Lecithaster gibbosus 
45.0 
2.0 (0.8-3.2) 
0.0 
0.0 
Parahemiurus merus 
5.0 
1.0 
2.1 
1.0 
33.3 
1.3 (1.1-1.5) 
Didymozoidae 
0.0 
0.0 
41.2 
1.8 (1.2-2.2) 
CESTODA 
Tetraphyllidea 
5.0 
1.00 
0.0 
0.0 
