Lo et al. Biomass and reproductive status of Sardinops sagax off the Pacific coast. 
177 
trawls. Data from the added trawls 
were excluded in estimating the total 
biomass to avoid bias. For the two 
March surveys, all locations (fixed 
stations and between-transects) were 
trawled regardless of spawning or 
acoustic signals (Figs. 3 and 5). The 
total number of trawls for each sur- 
vey was close to 50 (Table 1). 
For each trawl, the total weight 
(kg) of the Pacific sardine catch was 
recorded and up to 50 Pacific sardine 
were randomly sampled from each 
trawl where sardine were caught 
(hereafter referred to as a “positive 
trawl”). Sex was determined for each 
fish, and standard length (SL) and 
weight were measured. For the female 
fish, the ovaries were first examined 
for torpedo shape and or development 
of visible oocytes (yolking or hydrat- 
ing). When oocytes were not visible 
and the ovary was small, clear, and 
torpedo shaped, the ovary was re- 
corded as code 1 (clearly immature). 
Otherwise, the additional ovarian 
codes 2 (intermediate), 3 (active), or 
4 (hydrated) (Table 2) were used to 
identify potentially mature females — 
because only histological analysis can 
verify sardine maturity with certain- 
ty (Macewicz et al., 1996). All ovaries 
were removed and preserved in 10% 
neutral buffered formalin. If a 50- 
fish subsample did not have 25 po- 
tentially mature females (ovary codes 
2-4), more females were sampled to 
attain 25 per trawl for estimation 
of reproductive parameters used for 
computing spawning biomass. Addi- 
tional females were also processed to 
estimate batch fecundity, but were 
not included in the original random 
subsample for length distributions. 
We also obtained length distribu- 
tions based on data from commercial 
purse seine catches off the PNW in 
the summer seasons and from a test 
purse seine set in March 2005. 
48°N 
46°N 
44°N 
42°N 
29 February-19 March 2004 
hf. 
*&:: ■ : ■ 
Astoria . WASHINGTON 
OREGON 
V 
/ Coos Bay 
OREGON 
CALIFORNIA 
40 >^ 
38 ^ 4 ? 
36°N 
34°N 
32°N 
30°N 
N 
# Positive CalVET 
Negative CalVET 
a 0<egg density from CUFES<1 eggs/min 
& Egg density from CUFES>1 eggs/min 
■ j High density spawning regi 
★ Positive sardine trawls 
☆ Negative sardine trawls 
Temperature contours are °C 
I 1 
128°W 126°W 124°W 122°W 120°W 118°W 116°W 
Seasonal biomass 
A swept-area method was used to 
estimate the total biomass of Pacific 
sardine in summer and spring based 
on July and March trawl data, respec- 
tively. Because the efficiency of the 
trawl catch has not been evaluated, 
the biomass estimates must be con- 
sidered as relative and minimum 
Figure 3 
Locations of trawl (stars) and California vertical egg tows (CalVET: circles), 
for 2004 March ichthyoplankton-trawl survey off the Pacific Northwest 
(top map), and locations of trawls, CalVET tows (circles), and continuous 
underway egg sampling (CUFES: triangles) for the March-April 2004 
California Cooperative Oceanic Fisheries Investigations (CalCOFI) daily 
egg production survey (bottom map). Solid symbols indicate that Pacific 
sardine ( Sardinops sagax) were captured in the sample at that site. Con- 
tours are sea surface temperatures (°C). The dashed vertical line at 125°W 
longitude (seen in top map) is the divider of the two sampling strata. The 
shaded area on the bottom is the identified spawning habitat. 
