Javor et al.: Otolith morphometries and population structure of Sardmops sagax along the west coast of North America 
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Studies of tank-reared fish have led to insights into 
how specific environmental influences affect otolith 
shape and size. In some cases, feeding condition may 
affect growth and otolith morphology (Fletcher, 1995; 
Strelcheck et al., 2003; Gagliano and McCormick, 2004; 
Hussy, 2008). Temperature influenced otolith size in 
tank-reared fish (Hpie et al., 1999) and was inferred 
to regulate otolith growth in natural populations of 
Merluccius spp. and Coelorhynchus spp. (Lombarte and 
Lleonart, 1993; Bolles and Begg, 2000). Otolith mor- 
phometry, however, did not vary significantly with tem- 
perature or feeding condition in the Japanese flounder 
(Paralichthys olivaceus) (Katayama and Isshiki, 2007). 
Pacific sardine inhabit coastal waters of a broad tem- 
perature range, from <10°C in Oregon and Washington 
(Emmett et al., 2005) to >25°C in southern Baja Califor- 
nia (Felix-Uraga et al., 2004, 2005). Using temperature- 
at-catch data and otolith morphometry, Felix-Uraga et 
al. (2004, 2005) showed that the proposed north-south 
migration patterns of sardines supported the idea of 
three stocks in Baja California. The southern, warm- 
water otoliths were most differentiated from the rest, 
especially from those taken in coldest water catches. 
The authors performed multivariate discriminant anal- 
ysis on over 1000 otoliths, using four straight linear 
measurements. Although they revealed statistical sig- 
nificance, the results showed a high degree of overlap 
between collection sites (Ensenada and Bahia Magda- 
lena, ca. 500 km apart). That study did not address 
the cold-water stocks in the United States and Canada. 
Our overall goal was to evaluate the efficacy of oto- 
lith morphometries as a tool to identify Pacific sardine 
stocks for fishery management. One specific purpose 
of this investigation was to compare age-1 otoliths 
throughout their geographic range to detect regional 
differences and similarities by using several statistical 
approaches. Because sardine otoliths elongate asym- 
metrically as they grow, we applied a novel statistical 
approach that accommodated such changes, with the 
use of perimeter-weight profiles (PWPs), in addition to 
multivariate analysis of variance (MANOVA), princi- 
pal component analysis (PCA), and generalized linear 
modeling (GLM). A second objective was to compare 
regional and age-related attributes in northern and 
southern California cohorts of recruits over multiple 
years. This research paralleled 1) a multiyear study of 
southern California sardine in the live bait industry, 
2) an investigation of the microchemistry (trace ele- 
ments and stable isotopes) of a subset of otoliths from 
the same multiyear study, and 3) genetic analysis of 
sardine tissues (Dorval et al., 2011; B. Javor, unpubl. 
data). 
Materials and methods 
Collections 
Either whole fish or otoliths were collected from sites 
between Vancouver Island, British Columbia, Canada, 
Figure II 
Map of the North American collection sites for Pacific 
sardine ( Sardinops sagax ) for determination of coast- 
wide population structure from otolith morphometries. 
Details of the collections are given in Table 1. 
and the Gulf of California, Mexico (Table 1, Fig. 1). 
Samples from Canada, the Pacific Northwest, and Mexico 
were provided by other researchers investigating those 
populations. Samples from California were either spe- 
cifically targeted in our study or were collected as part 
of regular port sampling by the California Department 
of Fish and Game (CDFG). No standard length (SL) or 
fish weight data were available for many of the otoliths 
obtained from archived CDFG collections. 
The collections were divided into seven geographic 
groups that reflect oceanographic or political boundar- 
ies relevant to national fisheries: 1) Canada (Can); 2) 
Pacific Northwest (PNW), which includes Oregon and 
Washington; 3) Northern California (Monterey [Mon]); 
4) Southern California Bight (SoCal), 32°-35°N, which 
includes San Diego (SD) and Los Angeles; 5) Ensenada 
(Ens); 6) Bahia Magdalena (BMag); and 7) Gulf of Cali- 
fornia (Gulf). Humboldt Bay (Hum, region 2\3 between 
the Pacific Northwest and Monterey) and Port Hueneme 
(PH, region 3\4 between northern and southern Cali- 
fornia) were considered to be transitional zones based 
on oceanographic features. 
Otolith measurements 
Sardine sagittal otoliths are asymmetric and lend 
themselves to measurements between multiple land- 
