440 
Ocean distribution of the American shad 
{Alosa sapicfissima ) along the Pacific coast 
of North America 
William G. Pearcy (contact author ) 1 
Joseph P. Fisher 2 
Email address for contact author: wgpearcy@coas.oregonstate.edu 
1 College of Oceanic and Atmospheric Sciences 
Oregon State University 
Corvallis, Oregon 97331 
2 Cooperative Institute for Marine Resources Studies 
Hatfield Marine Science Center 
Oregon State University 
Newport, Oregon 97365 
Abstract — We examined the inciden- 
tal catches of American shad ( Alosa 
sapidissima ) taken during research 
cruises and in commercial and rec- 
reational landings along the Pacific 
coast of North America during over 
30 years of sampling. Shad, an intro- 
duced species, was mainly found over 
the shallow continental shelf, and 
largest catches and highest frequency 
of occurrences were found north of 
central Oregon, along the coasts of 
Washington and Vancouver Island, 
and in California around San Fran- 
cisco Bay. Migrations to the north off 
Washington and Vancouver were seen 
during spring to fall, but we found 
no evidence for large-scale seasonal 
migrations to the south during the 
fall or winter. The average weight of 
shad increased in deeper water. Sizes 
were also larger in early years of the 
study. Most were caught over a wide 
range of sea surface temperatures 
(11-17°C) and bottom temperatures 
(6.4-8.0°C). Abundance of shad on the 
continental shelf north of 44°N was 
highly correlated with counts of shad 
at Bonneville Dam on the Columbia 
River in the same year. Counts were 
negatively related to average weights 
and also negatively correlated with 
the survival of hatchery coho salmon 
(Oncorhynchus kisutch), indicating 
that survival of shad is favored by 
warm ocean conditions. Examining 
the catch during research cruises and 
commercial and recreational landings, 
we concluded that American shad 
along the Pacific coast have adapted 
to the prevailing environmental con- 
ditions and undertake only moderate 
seasonal migrations compared with 
the long seasonal migrations of shad 
along the Atlantic coast of North 
America. We suggest that the large 
spawning populations in the Columbia 
River and San Francisco Bay areas 
explain most of the distributional fea- 
tures along the Pacific coast. 
Manuscript submitted 1 April 2011. 
Manuscript accepted 22 July 2011 
Fish. Bull. 109:440-453 (2011). 
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. 
American shad (Alosa sapidissima), 
the largest member of the family Clu- 
peidae, is a euryhaline, anadromous 
fish native to the east coast of North 
America, where it ranges from Florida 
to the Bay of Fundy. American shad 
undertake extensive ocean migrations 
along the east coast of North America 
to the north in the summer, and south 
in the fall and winter, before returning 
to natal rivers in the spring to spawn. 
Adults usually spend 3-6 years in 
the ocean before returning to spawn 
in natal rivers. Juveniles migrate 
downstream in the fall, but some may 
reside in estuaries more than a year 
(Talbot and Sykes, 1958; Walburg 
and Nichols, 1967; Leggett, 1973). 
According to tagging studies, their 
extensive ocean migrations, of some- 
times thousands of kilometers during 
one season, are closely correlated 
with 13-18° sea surface isotherms 
(Leggett, 1973; Leggett and Whit- 
ney, 1972) and 7-13°C bottom tem- 
peratures (Neves and Depres, 1979). 
Little is known about the ocean life 
of American shad (hereafter referred 
to as “shad”) along the west coast of 
North America, although long mi- 
grations, like those in the Atlantic, 
have been postulated (Leggett and 
Whitney, 1972; Moyle, 1976; Peters- 
en et al., 2003). We examine recent 
catches of American shad along the 
Pacific coast of North America from 
research surveys, 1977-2008, as well 
as from landings of shad by commer- 
cial or sport vessels, thus expand- 
ing the data provided for the Pacific 
coast by Petersen et al. (2003) and 
Leggett and Whitney (1972). We com- 
pare similarities in distributions and 
seasonal migrations along the Pacific 
coast with those along the Atlantic 
coast of North America. 
American shad were first intro- 
duced to the Pacific coast of North 
America from the eastern United 
States in 1871. About ten thousand 
shad from the Hudson River were 
released into the Sacramento River 
after shipment across the country in 
8-gallon (31.3-L) milk cans by the 
California Fish Commission (Green, 
1874). Several other shipments were 
made between 1871 and 1881 (Smith, 
1896). Shad migrated rapidly to the 
north and south. They were intro- 
duced into the Columbia River, and 
the Willamette and Snake rivers, in 
1885 and 1886 (Skinner, 1962; Craig 
and Hacker, 1940). However, shad 
had appeared in the Columbia River 
several years before these introduc- 
tions, and this occurrence indicated 
the rapid movements of fish planted 
earlier in California (Welander, 1940; 
Oregon Fish Commission, 1951). Shad 
eventually were found in British 
Columbia in 1891, and later as far 
north as Alaska and as far south as 
Baja California (Hart, 1973). They 
have been reported as far west as 
Kamchatka, Russia, but established 
spawning populations there are not 
known (Chereshnev and Zharnikov, 
1989). 
