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Fishery Bulletin 108(4) 
Postsettleinent 
increments 
Pelagic increments 
Settlement 
mark 
Figure 2 
Growth increments in the otolith of a blue rockfish ( Sebastes 
mystinus). The settlement mark and increments produced before 
(pelagic) and after (post) settlement are indicated. 
the next. Transformation from the larval to 
the juvenile stage was ascertained by the oc- 
currence of secondary growth primordia (areas 
of new increment growth that form away from 
the otolith core; Laidig et ah, 1991). This trans- 
formation occurs during the planktonic stage 
before settlement. Duration of the pelagic juve- 
nile stage was estimated as the number of in- 
crements occurring from the secondary growth 
primordia to the settlement mark. Settlement 
date was calculated by subtracting the number 
of increments formed after the settlement mark 
from the collection date, and birth date was 
determined by subtracting the total number 
of increments in the otolith from the collection 
date. The otolith increments deposited during 
the pelagic juvenile stage followed a regular 
pattern, increasing in width with fish age (Fig. 
2). The settlement mark was the increment 
where a change in the depositional pattern of 
the increments was observed after the pelagic 
juvenile stage; typically the increment mark- 
ing settlement is narrower than the preceding 
increments (Amdur, 1991). To be considered 
the settlement mark, this change in increment 
width had to be visible from the settlement 
mark to the outer edge of the otolith and not 
just in one section. Often the settlement mark 
was evident in the otolith as a dark ring of 
numerous closely spaced increments. After the settle- 
ment mark, increment widths followed no consistent 
growth pattern. 
Oceanographic data 
Upwelling data were derived from monthly sea level pres- 
sure fields provided by the U.S. Navy Fleet Numerical 
Meteorology and Oceanography Center (data acquired 
from NMFS, Environmental Research Division, South- 
west Fisheries Science Center at http://www.pfeg. 
noaa.gov, accessed July 2009) measured off Mendocino 
(39°11'N lat., 123°58'W long.) and Monterey (36°47'N 
lat., 122°24 , W long.), California. Sea level anomaly data 
(adjusted for local atmospheric conditions) were collected 
from shore stations at Humboldt Bay (40°46'N lat., 
124°13'W long.) and Monterey (36°36'N lat., 121°53'W 
long.), California, and monthly means were obtained 
from the University of Hawaii Sea Level Center. These 
data represent a measure of change in sea level height 
over time and reflect water movement a positive anom- 
aly was associated with poleward flow and a negative 
anomaly was associated with equatorward flow. 
Two-way analysis of variance was used to test the 
hypotheses that mean settlement date, mean birth date, 
mean duration of pelagic larval and juvenile stages, and 
mean settlement age did not differ significantly between 
the two study areas. Principal components analysis 
(PCA) was used to evaluate the relationship among the 
otolith data (settlement date, birth date, and settlement 
age) and the oceanographic variables (monthly average 
upwelling and sea level anomalies for January-June) 
for both areas. Canonical correlation analysis (CCA) 
of the oceanographic and otolith data was used to ex- 
amine the possible causes of changes in interannual 
settlement dates. 
Resuits 
A total of 112 otoliths were examined (56 otoliths each 
from Mendocino and Monterey; Table 1). Sampling dates 
ranged from 2 June to 11 September each year, vary- 
ing from 1 to 34 days between the two study areas in 
a particular year. Fish sizes ranged from 37 to 73 mm 
standard length (SL) for Mendocino and from 38 to 68 
mm SL for Monterey. 
Average birth dates varied annually, with a differ- 
ence of 7-30 days between locations and an average of 
19 days difference over all years (Fig. 3). Birth dates of 
Mendocino rockfish were always later in the year than 
those of rockfish from Monterey (significantly different 
in 1994, 2001, and 2002; P< 0.05). Birth dates ranged 
from 4 January to 25 March for Mendocino fish (7 Feb- 
ruary average) and from 22 December to 9 March for 
Monterey fish (19 January average). 
Average settlement dates were significantly different 
(PcO.001) each year between the two locations, with 
fish from Mendocino always settling later in the year 
than fish from Monterey (23 days average; Fig. 4). The 
difference in settlement between the two sites varied 
from an average of 17 to 29 days. The earliest date of 
