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Fishery Bulletin 107(3) 
trient availability and production (Largier et al., 1997). 
Hence, spatial patterns of habitat use and quality for 
juvenile flatfish in classical and “Mediterranean-type” 
estuaries may differ substantially. 
Use of habitat by juvenile flatfish has been re- 
lated mostly to temperature, salinity, dissolved oxy- 
gen, substrate type, and depth (Gibson, 1994; Able 
et al., 2005). The first three variables directly influ- 
ence metabolic processes, and hence abundance and 
growth (Gibson, 1997). Substrate type can be used as 
a proxy for food availability, and is related to success 
in predator avoidance (Gibson, 1994; Amezcua and 
Nash, 2001). Differences in distribution as a function 
of depth may be due to habitat partitioning among 
life stages (Kramer, 1990; Gibson, 1997). Because a 
direct assessment of juvenile habitat quality is diffi- 
cult, growth and density have served as proxies. These 
measures integrate the effect of biological factors and 
environmental conditions (Necaise et al., 2005; Gilliers 
et al., 2006). Specifically, estimates of recent otolith 
growth rates evaluated through the measurement of 
increment widths can be used as an integrative indi- 
cator of habitat quality and the suitability of environ- 
mental conditions over short time scales (Le Pape et 
al., 2003; Gilliers et al., 2006). The fine-scale temporal 
and spatial variation of growth rates can thus serve 
as indicators of habitat quality. 
The use of otolith marginal increment widths as indi- 
cators of habitat quality relies on two premises. First, 
there must be a high correlation between somatic and 
otolith growth rates (Campana and Jones, 1992). This 
has been shown to be the case for juvenile California 
halibut (Kicklighter, 1990; Kramer, 1991). Secondly, 
differences in growth rates should reflect the quality 
of the habitat in which fish were captured (Sogard, 
1992; Gilliers et al., 2006). The second premise can 
be rendered invalid if there is substantial movement 
to or from areas with different environmental condi- 
tions within the time interval used to evaluate growth. 
Haaker (1975) found little movement of tagged juvenile 
California halibut within Anaheim Bay in southern 
California. Tagging studies of age-0 winter flounder 
( Pseudopleuronectes americanus) and plaice ( Pleuro - 
nectes platessa) have also indicated limited displace- 
ment on the scale of a few hundred meters (Saucerman 
and Deegan, 1991; Burrows et al., 2004). However, 
Fodrie and Herzka (2008) used otolith microchemistry 
to reconstruct movement patterns of juvenile California 
halibut within an arid estuary and found that 8 out 
of 14 (57%) individuals moved among sections of the 
estuary over a two-month period. Likewise, Herzka 
et al. (2009) examined length-frequency distributions 
and recapture locations of tagged individuals and found 
simultaneous evidence of estuarine emigration and 
residency. If juveniles move substantially within an 
estuary, the implicit assumption that an individual 
has remained in the vicinity of its capture location 
for the time period over which growth is evaluated 
may be violated. Caging experiments guarantee that 
an individual has remained at a given location under 
measurable environmental conditions (Sogard, 1992). 
However, confinement has the potential to influence 
natural growth rates (Guindon and Miller, 1995). Cag- 
ing experiments and sampling of natural populations 
are thus complimentary approaches for using growth 
rates as proxies for habitat quality. 
We evaluated nursery habitat quality for juvenile 
California halibut ( Paralichthys californicus) in a sea- 
sonally arid estuary, Punta Banda Estuary in Baja 
California, Mexico, based on recent otolith growth rates 
and an index of feeding success in relation to feeding 
levels. To determine if specific sections of the estuary 
serve as preferred juvenile habitat, we assessed spatial 
and temporal variability in density and evaluated re- 
cent otolith growth rates in relation to environmental 
conditions. In addition, we tested the hypothesis that 
juvenile density is higher in areas that favor higher 
growth rates. We simultaneously performed caging ex- 
periments and sampled natural populations to assess 
growth rates in relation to environmental conditions. 
Materials and methods 
Study area 
Punta Banda Estuary is a medium-size (11-km 2 at high 
tide, 5-km 2 at low tide) protected embayment located 
within the Southern California Bight. It is located 100 
km south of the US-Mexico border on the Pacific side of 
Baja California, Mexico (Fig. 1). The estuary lies along 
the southeastern margin of Todos Santos Bay (31°42'- 
31°47'N lat and 116°37 -116°39'W long), a semiprotected 
coastal system. The L-shaped estuary is connected to 
the bay at its northern end through a 125-m inlet (Ortiz 
et al., 2003). The fastest current velocities are found 
within the main channel at the mouth (~1 m/s), where 
depths are 10-12 m (Pritchard et al., 1978). A channel 
runs along the main axis of the estuary and is flanked 
by shallow submerged or exposed flats at low tide. The 
depth of the main channel in the central and inner sec- 
tions of the estuary is shallow (<3 m) compared to the 
outer section (approximately 8 m, see Ortiz et al., 2003 
for a detailed bathymetry). Along the shorter axis, the 
main channel splits into different arms and the average 
depth is <1 m in relation to mean low water. Patches 
of eelgrass ( Zostera marina) are found in the central 
estuaries and there are tidal marshes along most of the 
banks. The bottom is sandy towards the outer reaches 
of the system and becomes increasingly silty toward the 
head (Ortiz et al., 2003). 
Because the estuary is located in a seasonally arid 
region, the estuary behaves mostly as a negative estu- 
ary, in that temperature and salinity increase from 
the mouth to the head, particularly during the warmer 
months (Alvarez-Borrego and Alvarez-Borrego, 1982). 
Temperature and salinity also exhibit variations asso- 
ciated with the semidiurnal tidal cycle because of the 
exchange of water with Todos Santos Bay. Maximum 
tidal range during spring tides is about 1.7 m. 
