60 
Fishery Bulletin 110(1) 
o 30 
< 1 > 
"O 
^ 50 n 
45 -Stratum 1 
Density (t/nmi 2 ) 
0-10 
• 10-100 
0 100-500 
® 500-1000 
• 1000-5000 
O 5000-10000 
125 122 
Longitude (°N) 
Figure 3 
Spatial distribution of biomass densities estimated for Pacific sardine ( Sardinops sagax)[left], jack 
mackerel (Trachurus symmetricMs)[middlel , and Pacific mackerel (Scomber japonicus) [right] for the 2008 
spring (top) and summer (bottom) surveys. The estimates are based on the acoustic volume backscattering 
coefficients (s v ; m 2 m -3 ) integrated from 10-70 m depth; the acoustic composition of the nearest trawl; 
and the average target strength of each species. Strata (dashed lines) were created after each cruise. 
The predicted “optimal” plus “good” sardine habitat (Zwolinski et al., 2011) is circumscribed (left plots, 
dotted lines). Pacific herring (Clupea pallasii), northern anchovy ( Engraulis mordax), and other coastal 
pelagic fish species are not included owing to their low biomasses and the high sampling uncertainties 
for these species. 
