Pearcy and Fisher: Ocean distribution of Aiosa sapidissima along the Pacific coast of North America. 
441 
Adult and juvenile shad have been reported in ma- 
ny bays and estuaries along the west coast of United 
States from Grays Harbor, Washington, to San Fran- 
cisco Bay, California (Emmett et al 1 ). Their distribution 
in inland and coastal waters along the Pacific coast is 
known mainly from fishery landings. Large commercial 
catches of shad have been made in rivers in Oregon, 
Washington, and California. A fishery existed in the 
Columbia River, as well as in Oregon coastal streams 
in the early 1900s. Landings in other rivers (Siuslaw, 
Umpqua, Smith, Coos, and Coquille) in Oregon, where 
shad spawned, averaged 192 metric tons per year (t/yr) 
during 1962-72 (Mullen and Conover 2 ). The fishery in 
the Umpqua River landed an average of 180 t annually 
after 1923 (Skinner, 1962). Each of these rivers appar- 
ently supported its own spawning run of shad, although 
some recoveries of tagged fish have been reported in 
other rivers (Mullen 3 ). In the Columbia River, counts 
of shad passing Bonneville Dam to spawn during May 
through July have increased greatly over the past 70 
years because of the completion of dams and creation 
of large reservoirs, from fewer than 17,000 before 1960 
to over 2-5 million after 1990 (www.cbr.washington. 
edu/dart/, accessed November 2010). Several hundred 
thousand shad are landed annually by commercial and 
sport fisheries in the Columbia River (Petersen et al., 
2003). Adults are even found in the Snake River above 
Lower Granite Dam, 600 km from the ocean (Quinn 
and Adams, 1996). However, the major spawning areas 
for shad in the Columbia River are thought to be below 
Bonneville Dam where large numbers of juvenile shad 
are found in the estuary (Cleaver, 1951; Oregon Fish 
Commission, 1951; Hamman, 1981; Petersen et al., 
2003). In Washington, breeding populations of shad are 
known from Puget Sound, the Chehalis River, and Wil- 
lapa Bay (Wydoski and Whitney, 2003; Emmett et al. 1 ). 
In California, large runs of shad migrate into the 
Sacramento-San Joaquin River Delta to spawn where 
juvenile shad have been collected. Smaller runs are 
found in the Klamath, Eel, Salinas, and Russian rivers 
(Skinner, 1962; Allen et ah, 2006; CDFG 4 S ). The shad 
fishery in the San Francisco Bay area peaked in 1917 
when over 2500 t were landed. Between 1918 and 1945 
1 Emmett, R.L., S.A. Hinton, S.L. Stone and M.E. Monaco. 
1991. Distribution and abundance of fishes and inverte- 
brates in west coast estuaries. Volume 11: species life history 
summaries. ELME Report 8, 329 p. NOAA/NOS Strategic 
Environmental Assessments Division, Rockville, MD. 
2 Mullen, R. E., and K. R. Conover. 1973. Ecology of shad 
and striped bass in coastal rivers and estuaries, 12 p. Fish 
Comm. Oregon, Project No. AFC 53, Portland, OR. 
3 Mullen, R. E. 1974. A summary of American shad (Aiosa 
sapidissima) tagging studies on the coastal streams of Oregon, 
1946-70. Coastal Rivers Investigation, Inf. Rep. 74-3, 43 
p. Fish Comm. Oregon, Portland, OR. 
4 CDFG (California Department of Fish and Game). 2010. 
Effects of delta inflow and outflow on several native, rec- 
reational, and commercial species. DFG Exhibit 1, unpubl. 
report, 39 p. California Department of Fish and Game, 830 
S Street, Sacramento, CA 95811. 
the catch averaged 362 to 1800 t and then declined. In 
1957 the commercial fishery in the bay was closed and 
there now exists only a sport fishery (Skinner, 1962; 
Moyle, 1976). 
Shad were first reported in British Columbia in 1891; 
small numbers were caught between 1914 and 1946 
in fresh water. They were also reported from several 
regions in the ocean along the coast (Carl et al., 1959), 
but according to McPhail (2007), there is no evidence 
of reproduction in British Columbia. 
Our objectives were to document the distributional 
patterns of American shad along the Pacific coast of 
North America and to compare these patterns with 
those known from the Atlantic coast. 
Materials and methods 
American shad were captured incidentally in both 
pelagic and benthic research surveys from 1977 through 
2008 from California to British Columbia, as well as in 
commercial and recreational fisheries. National Oce- 
anic and Atmospheric Administration’s (NOAA) Alaska 
Fisheries Science Center (AFSC) triennial bottom trawl 
surveys from 1977 to 2004 provided extensive data on 
shad catches. Nor ’eastern trawls (with 27.4-m head-rope 
and 12.7-cm mesh in the body, 9-cm mesh in the codend 
and a 3.2-cm stretch mesh liner) were fished during 
the day at about 5.6 km/h for one half hour and from 
depths of 55 to 500 m during the months of May through 
September, 1977-2004 (Stauffer, 2004). Cruises began 
during different months of the year, beginning in Cali- 
fornia and progressing northward to Vancouver Island. 
Shad were also caught by the Northwest Fisheries 
Science Center (NWFSC) in bottom trawls (Aberdeen- 
style high-opening net, 26-m head rope, 3.8 cm liner 
in the codend), fished during the daytime to depths 
of 55-1280 m at a nominal tow duration of 15 min on 
the bottom at 4.0 km/h, mainly from late May to late 
July (early cruise) and again from late August to late 
October (late cruise), 2003-08. The trawl surveys were 
conducted according to a random-stratified sampling 
design (Keller et al., 2008). Biomass caught in both the 
AFSC and NWFSC trawls was converted to average 
weight per shad by dividing the total biomass by the 
total number of shad caught. Stepwise multiple regres- 
sion models were used to relate size of shad to bottom 
depth, day of year, sea surface temperature (SST), and 
bottom (gear) temperature during the 10 years of AFSC 
surveys, and to bottom depth and day of year during 
the six years of the NWFSC surveys (SST data for 
the NWFSC cruises were not available). Catches were 
also related to the Pacific Decadal Oscillation (Mantua 
et al., 1997), Oregon Production Index (OPI) survival 
estimates generated from hatchery releases of coho 
salmon (O ncot'liynchus kisutch) smolts and returns of 
adult coho salmon to hatcheries, and counts of shad 
passing the Bonneville Dam. Shad were also caught 
in pelagic surveys targeting juvenile salmonids from 
1981 to 2008 off Oregon and Washington. The purse 
