176 
Fishery Bulletin 108(2) 
48°N 
46°N 
44°N 
42°N 
40°N 
48°N 
46°N 
44°N 
42°N 
40°N 
• Positive CalVET 
o Negative CalVET 
▲ 0<egg density from CUFES<0.5 eggs/min! 
J i Egg density from CUFES>0 5 eggs/min 
|~j High density spawning region j 
Temperature contours are °C 
California 
100 
200 
128°W 
126°W 
124°W 
122°W 
128°W 
126°W 
124°W 
122“W 
Figure 2 
(A) Locations of trawls (stars) used for the estimation of biomass of Pacific sardine (Sardinops sagax), excluding added 
trawls in the inshore area (Table 1), and (B) locations of California vertical egg tows (CalVET: circles) and where con- 
tinuous underway egg samples were taken (measured in eggs per minute (CUFES: triangles). Contours are sea surface 
temperatures (°C). The dashed vertical line is the 125°W longitude divider of the two sampling strata. The offshore 
shaded area in (B) is the major spawning habitat. Positive tows were those tows during which sardine were caught. 
Negative tows were tows when sardine were not caught. 
station activities were performed between twilight and 
dawn, whereas CalVET and CUFES samples were col- 
lected throughout all 24 hours. At each station, a Cal- 
VET sample was collected and sea surface temperature 
(SST) was recorded, whereas between stations, CUFES 
samples and water temperature were taken at a fixed 
3-m depth (Figs. 2 and 4). The CUFES data were used 
primarily to map the spawning area based on the den- 
sity of sardine eggs. 
A Nordic 264 trawl (NET Systems, Bainbridge Is- 
land, WA), with a vertical opening of 20 m, a mouth 
area of approximately 360 m 2 , and a 7-mm codend 
mesh (Emmett et ah, 2005), was towed to sample the 
upper 18-20 m of the water column. The distance trav- 
eled by each trawl was recorded and was later con- 
verted to the volume sampled. The swept area (m 2 ) 
is the volume (m 3 ) divided by 20 m. During the July 
2003 survey, few trawls were taken in the offshore 
area. Additional trawls were taken inshore to collect 
extra samples to determine reproductive parameters 
in areas of sardine spawning activity identified by 
sardine egg densities in CUFES samples or the pres- 
ence of schools as indicated by acoustic signals (Fig. 2). 
Similarly, during July 2004, trawls were taken in the 
southern spawning area off Port Orford, OR (Fig. 4), 
in addition to the prepositioned and between-transect 
