52 
Abstract — During the last century, 
the population of Pacific sardine 
( Sa?'dinops sagax ) in the California 
Current Ecosystem has exhibited 
large fluctuations in abundance and 
migration behavior. From approxi- 
mately 1900 to 1940, the abun- 
dance of sardine reached 3.6 million 
metric tons and the “northern stock” 
migrated from offshore of California 
in the spring to the coastal areas near 
Oregon, Washington, and Vancouver 
Island in the summer. In the 1940s, 
the sardine stock collapsed and the 
few remaining sardine schools con- 
centrated in the coastal region off 
southern California, year-round, for 
the next 50 years. The stock gradu- 
ally recovered in the late 1980s 
and resumed its seasonal migra- 
tion between regions off southern 
California and Canada. Recently, a 
model was developed which predicts 
the potential habitat for the north- 
ern stock of Pacific sardine and 
its seasonal dynamics. The habitat 
predictions were successfully vali- 
dated using data from sardine sur- 
veys using the daily egg production 
method; scientific trawl surveys off 
the Columbia River mouth; and com- 
mercial sardine landings off Oregon, 
Washington, and Vancouver Island. 
Here, the predictions of the poten- 
tial habitat and seasonal migration 
of the northern stock of sardine are 
validated using data from “acoustic- 
trawl” surveys of the entire west coast 
of the United States during the spring 
and summer of 2008. The estimates 
of sardine biomass and lengths from 
the two surveys are not significantly 
different between spring and summer, 
indicating that they are representa- 
tive of the entire stock. The results 
also confirm that the model of poten- 
tial sardine habitat can be used to 
optimally apply survey effort and 
thus minimize random and system- 
atic sampling error in the biomass 
estimates. Furthermore, the acous- 
tic-trawl survey data are useful to 
estimate concurrently the distribu- 
tions and abundances of other pelagic 
fishes. 
Manuscript submitted 13 June 2011. 
Manuscript accepted 29 September 2011. 
Fish. Bull. 110:52-70(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. 
Prediction and confirmation of seasonal migration 
of Pacific sardine ( Sardinops sagax ) 
in the California Current Ecosystem 
David A. Denier (contact author) 
Juan P. Zwolinski 
Kyle A. Byers 
George R. Cutter 
Josiah S. Renfree 
Thomas S. Sessions 
Beverly J. Macewicz 
Email address for contact author: david.demer@noaa.gov 
Southwest Fisheries Science Center 
Fisheries Resources Division 
8604 La Jolla Shores Drive 
La Jolla, California 92037 
Pacific sardine ( Sardinops sagax) in 
the California Current Ecosystem 
(CCE) vary greatly in terms of their 
abundance and migration behavior. 
For example, from approximately 1900 
to 1940, sardine was the most abun- 
dant coastal pelagic fish species (CPS) 
in the CCE (Radovich, 1982), with its 
biomass estimated to be 3.6 million 
metric tons (Mt; MacCall, 1979). Tag- 
ging studies (Clark and Janssen, 1945) 
indicated that the “northern stock” 
resided largely off California in the 
spring, and off Oregon, Washington, 
and Vancouver Island in the summer. 
In the 1940s, the sardine stock, and 
thus the fishery, abruptly collapsed. 
During the subsequent 50 years of low 
abundance, the few remaining sardine 
schools concentrated in the coastal 
region off southern California (Mac- 
Call, 1976). With the gradual recovery 
of the stock in the late 1980s (Jacob- 
son and MacCall, 1995; Wolf, 1992), 
perhaps due to the combination of 
conservation measures and favorable 
environmental conditions, sardine 
in the CCE expanded their biomass 
and distribution and resumed their 
seasonal migration between regions 
off southern California and Canada 
(McFarlane and Beamish, 2001). In 
the 1990s, Pacific mackerel ( Scomber 
japonicus) had become scarce and 
the fishery shifted back to target- 
ing sardine (Mason, 2004). The com- 
bined landings of sardine off the west 
coasts of Mexico, the United States 
(U.S.), and Canada peaked at 0.12 
Mt in 2007, driven mostly by the re- 
opening of the fishery in the northeast 
Pacific. The Pacific Fishery Manage- 
ment Council (PFMC) manages the 
sardine and Pacific mackerel fisheries 
using catch quotas based on annual 
stock assessments (Crone et ah, 2009; 
Hill et ah, 2010). 
Sardine surveys and assessments 
Since the mid-1980s, assessments of 
sardine in the CCE have been based 
on fisheries-independent estimates 
of their abundance from spring sur- 
veys off California conducted with the 
daily-egg-production method (DEPM; 
Lasker, 1985). Recent assessments 
of sardine biomass ranged from 1.3 
Mt in 2006 to 0.6 Mt in 2010 (Hill et 
ah, 2010). In 2009, the sardine catch 
was limited to 0.08 Mt (Hill et ah, 
2010). Concerned about assumptions 
in the DEPM and alarmed by the 
magnitudes and trend in catch quotas, 
the fishing industry resurrected the 
“optical-seine” method (Squire, 1972) 
[which combines information collected 
with cameras on aircraft and purse- 
seine nets deployed from fishing ves- 
sels] to survey sardine off Oregon 
and Washington during the summer 
