Origin and Dispersal of the Alewife, Alosa Pseudoharengus, and the Gizzard Shad, Dorosoma Cepedianum, in the Great Lakes

Abstract

It is possible that the alewife is native to Lake Ontario and the gizzard shad to Lake Erie, although conclusive evidence for this is lacking. There appear to be no records of the alewife from Lake Ontario prior to 1873, after the lake had been stocked with American shad. That species may still occur in Lake Ontario occasionally. A tabular comparison of these species is given to facilitate identification. The alewife is referred to the genus Alosa (rather than Pomolobus) because no reliable characteristics are available to distinguish the species of these two groups. Wilmot recorded a herring-like fish (not the American shad) from Lake Ontario about 1837 which probably was the gizzard shad, though it may have been the alewife. The first record of gizzard shad in Lake Ontario is for 1913, but the species was reported from Lake Erie in 1848, 18 years after the completion of the first canal to connect Lake Erie and the Ohio River. It is hypothesized that the gizzard shad entered Lake Erie in pre-Columbian times during a warm-dry period. A chronological record of the appearance of alewives in the upper Great Lakes shows the first specimen reported from Lake Erie was taken in 1931, Lake Huron 1933, Lake Michigan 1949, and Lake Superior 1954; actual dates of first appearance in each lake are unknown, but the species obviously moved from Lake Erie to the other lakes via Detroit River and Lake St. Clair. The alewife did not become abundant in Lake Erie or Lake Huron until around 1950 or in Lake Michigan until about 1956; it is widely distributed but not yet abundant in Lake Superior. The phenomenal increase in abundance and spreading of the alewife may be correlated with the upset in population balance by the sea lamprey; catch statistics for the alewife and shallow water cisco (Coregonus artedii) from South Bay, Lake Huron, suggest a direct or indirect causal relationship during 1954–1956. The gizzard shad does not occur north of lower New York Harbor (and there only rarely) on the Atlantic slope, although it has been reported from New Brunswick, where it was probably misidentified for the alewife. Its inland range has been extended by canal connections and perhaps it reached Lake Erie in this way; it definitely entered Lake Michigan through the Chicago River canal. A reference in 1874 to the “saw-belly” from the Great Lakes undoubtedly represents the gizzard shad, also known by that name. The species has evidently spread to Lake Ontario and the vicinity of Quebec by moving through the Welland Canal, and to Lake Huron via the Detroit River and Lake St. Clair. The first specimen known to be taken in Lake Michigan was caught on October 13, 1953, west of Muskegon, Michigan; another was taken near Gary, Indiana, on November 2, 1953. The gizzard shad has not been reported from Lake Superior where cold, deep water may prohibit its establishment. It has on occasion gained some commercial importance in Lakes Erie and Huron, where 31,600 pounds valued at $930 were taken in 1949. The gizzard shad may have been aided in expanding northward by the warming climatic trend of the past half century. The two species, particularly the alewife, are steadily increasing in abundance and methods of utilizing this new resource should be devised.