Lo et al. Biomass and reproductive status of Sardmops sagax off the Pacific coast. 
179 
A ( = the area (km 2 ) in stratum 
i, i=l (inshore) and 2 (off- 
shore). 
Note: the coefficient of variance (CV) 
of the estimate is CV(B) - SE (B)/B. 
Bootstrap simulation was used to esti- 
mate the bias of the estimate (Eq. 1), 
and the bias-corrected estimate (B c ) 
as B c =B-(B b -B), where B is computed 
from Equation 1, B h is the estimate 
from the bootstrap simulation, and the 
mean square error (MSE -variance + 
bias 2 ) of the biomass estimates (Eq. 2). 
We also computed a crude esti- 
mate of the recruit biomass (age- 
zero year or incoming year class) as 
ancillary information for compara- 
tive purposes for spring in 2004 and 
2005, based on the biomass of fish 
<120 mm SL because 120 mm was 
the break point for the length-fre- 
quency distribution in March surveys 
from this study (Fig. 6) and it was 
reported that age-0 sardine in the 
PNW were <110 mm (measured by 
fork length) (Emmett et al., 2005). 
Recruit biomass (B R ) was estimated 
by using Equations 1 and 2, where 
X t = the mean catch (kg/m 2 ) of fish 
<120 mm SL in the tth stratum ( X R ■ ). 
The catch of recruits for each trawl 
would be obtained as 
X R,ij= X i* U ij, length <120mm’ where X ij = 
the total catch from the yth trawl, 
and U lengths 120 mm = the Weight of fish 
<120 mm SL divided by the total fish 
weight based on our random samples 
with a maximum of 50 fish from each 
tow. 
Spawning habitat 
The spawning habitat was defined as 
the area of relatively high egg densi- 
ties during early summer, because 
June-July was the peak spawning 
time for Pacific sardine off the PNW 
as determined from egg and larval 
data collected in the mid-1990s (Bent- 
ley et al., 1996). Because the number 
of positive CalVET tows was low (four 
of 54 tows during July 2003 and 3 of 
48 tows during July 2004), we chose to 
use data from CUFES sampling. The 
spawning habitat area was defined 
as the area where the majority of egg 
densities exceeded a threshold of 0.5 
eggs/min because the egg densities 
were generally low. Off California, 
48°N - 
46°N 
44°N - 
42°N 
36°N 
34°N - 
32°N 
128°W 
126°W 
124°W 
122°W 
120°W 
118°W 
116°W 
40'X, 
38 °^ 
30°N 
Temperature contours are °C 
• Positive CalVET 
Negative CalVET 
* 0<egg density from CUFES<1 eggs/min 
± Egg density from CUFES>1 eggs/min 
fH High density spawning region 
★ Positive sardine trawls 
☆ Negative sardine trawls 
) 
1 5 April— 
1 May 2005 
Long Beach 
2-21 March 2005 
Figure 5 
Locations of trawl (stars) and California vertical egg tows (CalVET: 
circles) for the 2005 March ichthyoplankton-trawl survey off the Pacific 
Northwest (top) and trawls, CalVET tows (circles), and continuous 
underway egg samples (CUFES: triangles) for the April-May 2005 
California Cooperative Oceanic Fisheries Investigations (CalCOFI) 
daily egg production survey (bottom). Solid symbols indicate that Pacific 
sardine (Sardinops sagax) were captured in the sample at that site. 
Contours are sea surface temperatures (°C). The dashed vertical line 
is the 125°W longitude divider of the two sampling strata. The shaded 
area is the spawning habitat. 
