110 
Abstract — The abundances and 
distributions of coastal pelagic fish 
species in the California Current Eco- 
system from San Diego to southern 
Vancouver Island, were estimated 
from combined acoustic and trawl 
surveys conducted in the spring of 
2006, 2008, and 2010. Pacific sar- 
dine ( Sardinops sagax), jack mack- 
erel ( Trachurus symmetricus ), and 
Pacific mackerel (Scomber japonicus) 
were the dominant coastal pelagic 
fish species, in that order. Northern 
anchovy ( Engraulis mordax) and 
Pacific herring ( Clupea pallasii) were 
sampled only sporadically and there- 
fore estimates for these species were 
unreliable. The estimates of sardine 
biomass compared well with those 
of the annual assessments and con- 
firmed a declining trajectory of the 
“northern stock” since 2006. During 
the sampling period, the biomass of 
jack mackerel was stable or increas- 
ing, and that of Pacific mackerel was 
low and variable. The uncertainties in 
these estimates are mostly the result 
of spatial patchiness which increased 
from sardine to mackerels to anchovy 
and herring. Future surveys of coastal 
pelagic fish species in the California 
Current Ecosystem should benefit 
from adaptive sampling based on mod- 
eled habitat; increased echosounder 
and trawl sampling, particularly for 
the most patchy and nearshore spe- 
cies; and directed-trawl sampling for 
improved species identification and 
estimations of their acoustic target 
strength. 
Manuscript submitted 13 June 2011. 
Manuscript accepted 2 November 2011. 
Fish. Bull. 110:110-122 (2012). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
Distributions and abundances of Pacific sardine 
(Sardinops sagax ) and other pelagic fishes 
in the California Current Ecosystem 
during spring 2006, 2008, and 2010, 
estimated from acoustic-trawl surveys 
Juan P. Zwolinski (contact author) 
David A. Denier 
KySe A. Byers 
George R. Cutter 
Josiah S. Renfree 
Thomas S. Sessions 
Beverly J. Macewicz 
Email address for contact author: Juan.Zwolmski@noaa.gov 
Advanced Survey Technologies Program 
Southwest Fisheries Science Center 
National Marine Fisheries Service 
National Oceanic and Atmospheric Administration 
8604 La Jolla Shores Drive 
La Jolla, California 92037 
The California Current Ecosystem 
(CCE) spans the west coast of North 
America (GLOBEC, 1992). As in 
most upwelling ecosystems, the CCE 
has high primary and secondary 
productivity and consequently high 
biomasses of lower- and middle-tro- 
phic-level species (Freon et ah, 2009). 
Four coastal pelagic fish species (CPS) 
appear to sequentially dominate the 
epipelagic fish biomass in the CCE: 
Pacific sardine ( Sardinops sagax), 
hereafter sardine; jack mackerel (Tra- 
churus symmetricus); Pacific mackerel 
(Scomber japonicus); and northern 
anchovy (Engraulis mordax), hereaf- 
ter anchovy (MacCall, 1996; Mason, 
2004). Sardine dominated in the first 
half of the 20 th century, then declined 
precipitously and the stock and the 
fishery collapsed. Jack mackerel were 
abundant in the 1950s, followed by 
anchovy in the 1960s and 1970s, and 
Pacific mackerel in the 1980s. Sardine 
returned to dominance during the 
following two decades (Mason, 2004; 
Moser et al., 2001). These alternations 
may be driven by natural cycles in the 
climate and ocean conditions (Chavez 
et ah, 2003) and are perhaps accentu- 
ated by fishing pressure (MacCall, 
1976; Radovich, 1982). 
The distributions of these CPS in 
the CCE depend on their total abun- 
dances, ages, and the season. For ex- 
ample, when the “northern stock” of 
sardine is large, the older fish can be 
found offshore of southern and cen- 
tral California during spring spawn- 
ing; and then nearshore off Oregon, 
Washington, and Vancouver Island 
during summer feeding (Clark and 
Janssen Jr., 1945; Lo et ah, 2011; 
Zwolinski et ah, 2011; Derner et ah, 
2012). In contrast, smaller sardine, 
age-0 and age-1, rarely venture far 
from their recruitment areas. 
Pacific mackerel are commonly 
found off southern California, and 
their distribution extends to southern 
Baja California (Parrish and Mac- 
Call, 1978). During 1980s to 1990s, 
when their stock abundance was 
high, Pacific mackerel were present 
off California and sustained a valu- 
able fishery. Currently, the fishery for 
Pacific mackerel off the west coast 
of the United States (U.S.) is small. 
Although there is a paucity of infor- 
mation about the current size of the 
Pacific mackerel stock, and its spatial 
and age distributions, its biomass is 
thought to be low and mostly resid- 
ing south of the U.S. -Mexico border 
