442 
Abstract — Settled juvenile blue rock- 
fish ( Sebastes mystinus) were collected 
from two kelp beds approximately 335 
km apart off Mendocino in northern 
California and Monterey in central 
California. A total of 112 rockfish 
were collected from both sites over 
5 years (1993, 1994, 2001, 2002, 
and 2003). Total age, settlement 
date, age at settlement, and birth 
date were determined from otolith 
microstructure. Fish off Mendocino 
settled mostly in June and fish off 
Monterey settled mostly in May (aver- 
age difference in settlement=23 days). 
Although the difference in the timing 
of settlement followed this same pat- 
tern for both areas over the five years, 
settlement occurred later in 2002 and 
2003 than in the prior years of sam- 
pling. The difference in the timing 
of settlement was due primarily to 
differences in birth dates for the 
two areas. The time of settlement 
was positively related to upwelling 
and negatively related to sea level 
anomaly for most of the months 
before settlement. Knowledge of the 
timing of settlement has implications 
for design and placement of marine 
protected areas because protection 
of nursery grounds is frequently a 
major objective of these protected 
areas. The timing of settlement is 
also an important consideration in the 
planning of surveys of early recruits 
because mistimed surveys (caused by 
latitudinal differences in the timing 
of settlement) could produce biased 
estimates. 
Manuscript submitted 4 May 2010. 
Manuscript accepted 27 July 2010. 
Fish. Bull. 108:442-449 (2010). 
The views and opinions expressed 
or implied in this article are those 
of the author (or authors) and do not 
necessarily reflect the position 
of the National Marine Fisheries 
Service, NOAA. 
Influence of ocean conditions on the timing 
of early life history events for blue rockfish 
(Sebastes mystinus) off California 
Thomas E. Laidig 
Email address: tom.laidig@noaa.gov 
Fisheries Ecology Division 
Southwest Fisheries Science Center 
National Marine Fisheries Service 
National Oceanic and Atmospheric Administration 
110 Shaffer Road 
Santa Cruz, California 95060 
Successful recruitment of fishes into 
adult populations can have a major 
influence on population biomass. 
Within a species, recruitment events 
can vary widely in magnitude both 
temporally and spatially (Doherty and 
Fowler, 1994; Ralston and Howard, 
1995; Caley et al., 1996). Under- 
standing this variability in recruit- 
ment strength is a critical goal in 
predicting adult population structure 
(Doherty and Fowler, 1994; Hidalgo 
et al., 2009). Knowledge of the spa- 
tial and temporal variability in 
recruitment of a population can lead 
to enhanced management of the spe- 
cies (e.g., to protection of important 
nursery areas) (Grorud-Colvert and 
Sponaugle, 2009). 
Variation in recruitment strength 
is influenced by multiple biotic and 
abiotic factors, including the mag- 
nitude of spawning biomass, preda- 
tion, available habitat, available prey, 
competition, temperature, upwelling, 
turbulence, water quality, and ocean 
currents (Peterman and Bradford, 
1987; Ainley et al., 1993; Ralston 
and Howard, 1995; Hobson et al., 
2001; Johnson et al., 2001; Sale et 
al., 2005; Hidalgo et al., 2009). Re- 
cruitment variability can occur from 
large-scale (e.g., El Nino or La Nina 
events, Pacific Decadal Oscillations) 
(Carr, 1991; Field and Ralston, 2005; 
Laidig et al., 2007) to small-scale pro- 
cesses (e.g., localized patchiness of 
suitable nursery habitats; fine-scale 
oceanographic events) (Sale et al., 
2005; Johnson, 2006). Determining 
the relative influence of these pro- 
cesses on fish recruitment has been 
a goal for many studies (Peterman 
and Bradford, 1987; Yoklavich et al., 
1996; Laidig et al., 2007). 
Annual recruitment of rockfishes 
( Sebastes spp.) in the northeast Pa- 
cific can vary by orders of magnitudes 
between years (Ralston and Howard, 
1995; Laidig et al., 2007). In addition 
to temporal variability in recruitment, 
latitudinal or spatial variability also 
has been observed for several rockfish 
species along the west coast (Sakuma 
et al., 2006). Variable recruitment 
leads to greater uncertainty in the 
prediction of year-class strength. 
Rockfishes give birth to larvae (par- 
turition) that survive in the plankton 
for several months before settling into 
nursery or adult habitats (Carr, 1991; 
Love et al., 2002; Ammann, 2004). 
For several rockfish species, it has 
been demonstrated that the strength 
of the year class is determined during 
this planktonic stage (Ralston and 
Howard, 1995; Laidig et al., 2007; 
Wilson et al., 2008) and that it can 
be affected further by postsettlement 
mortality from predation (Hobson et 
al., 2001). 
In this study, the recruitment of ju- 
venile blue rockfish (S. mystinus) from 
the pelagic environment to nearshore 
kelp beds was examined in two geo- 
graphic regions along the California 
coast. Blue rockfish are an important 
commercial and recreational species 
in California ranging from at least 
British Columbia to northern Baja 
California (Love et al., 2002). Otolith 
microstructure was used to estimate 
