440 Abstract—We examined the inciden- Ocean distribution of the American shad tal catches of American shad (Alosa sapidissima) taken during research (Alosa sapidissima) along the Pacific coast cruises and in commercial and rec- reational landings along the Pacific of North America coast of North America during over 30 years of sampling. Shad, an intro- William G. Pearcy (contact author)1 duced species, was mainly found over 2 the shallow continental shelf, and Joseph P. Fisher largest catches and highest frequency Email address for contact author: [email protected] of occurrences were found north of 1 College of Oceanic and Atmospheric Sciences central Oregon, along the coasts of Oregon State University Washington and Vancouver Island, Corvallis, Oregon 97331 and in California around San Fran- cisco Bay. Migrations to the north off 2 Cooperative Institute for Marine Resources Studies Washington and Vancouver were seen Hatfield Marine Science Center during spring to fall, but we found Oregon State University no evidence for large-scale seasonal Newport, Oregon 97365 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 American shad (Alosa sapidissima), ing the data provided for the Pacific (11–17°C) and bottom temperatures the largest member of the family Clu- coast by Petersen et al. (2003) and (6.4–8.0°C). Abundance of shad on the peidae, is a euryhaline, anadromous Leggett and Whitney (1972). We com- continental shelf north of 44°N was fish native to the east coast of North pare similarities in distributions and highly correlated with counts of shad America, where it ranges from Florida seasonal migrations along the Pacific at Bonneville Dam on the Columbia River in the same year. Counts were to the Bay of Fundy. American shad coast with those along the Atlantic negatively related to average weights undertake extensive ocean migrations coast of North America. and also negatively correlated with along the east coast of North America American shad were first intro- the survival of hatchery coho salmon to the north in the summer, and south duced to the Pacific coast of North (Oncorhynchus kisutch), indicating in the fall and winter, before returning America from the eastern United that survival of shad is favored by to natal rivers in the spring to spawn. States in 1871. About ten thousand warm ocean conditions. Examining Adults usually spend 3–6 years in shad from the Hudson River were the catch during research cruises and the ocean before returning to spawn released into the Sacramento River commercial and recreational landings, in natal rivers. Juveniles migrate after shipment across the country in we concluded that American shad downstream in the fall, but some may 8-gallon (31.3-L) milk cans by the along the Pacific coast have adapted to the prevailing environmental con- reside in estuaries more than a year California Fish Commission (Green, ditions and undertake only moderate (Talbot and Sykes, 1958; Walburg 1874). Several other shipments were seasonal migrations compared with and Nichols, 1967; Leggett, 1973). made between 1871 and 1881 (Smith, the long seasonal migrations of shad According to tagging studies, their 1896). Shad migrated rapidly to the along the Atlantic coast of North extensive ocean migrations, of some- north and south. They were intro- America. We suggest that the large times thousands of kilometers during duced into the Columbia River, and spawning populations in the Columbia one season, are closely correlated the Willamette and Snake rivers, in River and San Francisco Bay areas with 13–18° sea surface isotherms 1885 and 1886 (Skinner, 1962; Craig explain most of the distributional fea- (Leggett, 1973; Leggett and Whit- and Hacker, 1940). However, shad tures along the Pacific coast. ney, 1972) and 7–13°C bottom tem- had appeared in the Columbia River peratures (Neves and Depres, 1979). several years before these introduc- Little is known about the ocean life tions, and this occurrence indicated of American shad (hereafter referred the rapid movements of fish planted to as “shad”) along the west coast of earlier in California (Welander, 1940; North America, although long mi- Oregon Fish Commission, 1951). Shad grations, like those in the Atlantic, eventually were found in British have been postulated (Leggett and Columbia in 1891, and later as far Manuscript submitted 1 April 2011. Manuscript accepted 22 July 2011 Whitney, 1972; Moyle, 1976; Peters- north as Alaska and as far south as Fish. Bull. 109:440–453 (2011). en et al., 2003). We examine recent Baja California (Hart, 1973). They catches of American shad along the have been reported as far west as The views and opinions expressed Pacific coast of North America from Kamchatka, Russia, but established or implied in this article are those of the author (or authors) and do not necessarily research surveys, 1977–2008, as well spawning populations there are not reflect the position of the National Marine as from landings of shad by commer- known (Chereshnev and Zharnikov, Fisheries Service, NOAA. cial or sport vessels, thus expand- 1989). Pearcy and Fisher: Ocean distribution of Alosa sapidissima along the Pacific coast of North America. 441 Adult and juvenile shad have been reported in ma- the catch averaged 362 to 1800 t and then declined. In ny bays and estuaries along the west coast of United 1957 the commercial fishery in the bay was closed and States from Grays Harbor, Washington, to San Fran- there now exists only a sport fishery (Skinner, 1962; cisco Bay, California (Emmett et al1). Their distribution Moyle, 1976). in inland and coastal waters along the Pacific coast is Shad were first reported in British Columbia in 1891; known mainly from fishery landings. Large commercial small numbers were caught between 1914 and 1946 catches of shad have been made in rivers in Oregon, in fresh water. They were also reported from several Washington, and California. A fishery existed in the regions in the ocean along the coast (Carl et al., 1959), Columbia River, as well as in Oregon coastal streams but according to McPhail (2007), there is no evidence in the early 1900s. Landings in other rivers (Siuslaw, of reproduction in British Columbia. Umpqua, Smith, Coos, and Coquille) in Oregon, where Our objectives were to document the distributional shad spawned, averaged 192 metric tons per year (t/yr) patterns of American shad along the Pacific coast of during 1962–72 (Mullen and Conover2). The fishery in North America and to compare these patterns with the Umpqua River landed an average of 180 t annually those known from the Atlantic coast. 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 Materials and methods other rivers (Mullen3). In the Columbia River, counts of shad passing Bonneville Dam to spawn during May American shad were captured incidentally in both through July have increased greatly over the past 70 pelagic and benthic research surveys from 1977 through years because of the completion of dams and creation 2008 from California to British Columbia, as well as in of large reservoirs, from fewer than 17,000 before 1960 commercial and recreational fisheries. National Oce- to over 2–5 million after 1990 (www.cbr.washington. anic and Atmospheric Administration’s (NOAA) Alaska edu/dart/, accessed November 2010). Several hundred Fisheries Science Center (AFSC) triennial bottom trawl thousand shad are landed annually by commercial and surveys from 1977 to 2004 provided extensive data on sport fisheries in the Columbia River (Petersen et al., shad catches. Nor’eastern trawls (with 27.4-m head-rope 2003). Adults are even found in the Snake River above and 12.7-cm mesh in the body, 9-cm mesh in the codend Lower Granite Dam, 600 km from the ocean (Quinn and a 3.2-cm stretch mesh liner) were fished during and Adams, 1996). However, the major spawning areas the day at about 5.6 km/h for one half hour and from for shad in the Columbia River are thought to be below depths of 55 to 500 m during the months of May through Bonneville Dam where large numbers of juvenile shad September, 1977–2004 (Stauffer, 2004). Cruises began are found in the estuary (Cleaver, 1951; Oregon Fish during different months of the year, beginning in Cali- Commission, 1951; Hamman, 1981; Petersen et al., fornia and progressing northward to Vancouver Island. 2003). In Washington, breeding populations of shad are Shad were also caught by the Northwest Fisheries known from Puget Sound, the Chehalis River, and Wil- Science Center (NWFSC) in bottom trawls (Aberdeen- lapa Bay (Wydoski and Whitney, 2003; Emmett et al.1). style high-opening net, 26-m head rope, 3.8 cm liner In California, large runs of shad migrate into the in the codend), fished during the daytime to depths Sacramento–San Joaquin River Delta to spawn where of 55–1280 m at a nominal tow duration of 15 min on juvenile shad have been collected. Smaller runs are the bottom at 4.0 km/h, mainly from late May to late found in the Klamath, Eel, Salinas, and Russian rivers July (early cruise) and again from late August to late (Skinner, 1962; Allen et al., 2006; CDFG4). The shad October (late cruise), 2003–08. The trawl surveys were fishery in the San Francisco Bay area peaked in 1917 conducted according to a random-stratified sampling when over 2500 t were landed. Between 1918 and 1945 design (Keller et al., 2008).