CHITTENDEN: DYNAMICS OF AMERICAN SHAD RUNS 



migrate seaward after spawning. Added to this is 

 a large postspawning mortality in nontidal water 

 (Chittenden 1969). Fishing, in general, decreases 

 the age of the stock exploited. The historical and 

 recent effect of fishing on Delaware River stocks 

 is not completely clear, but this was probably a 

 much more important factor before 1910 when 

 commercial landings were as high as 14 to 17 

 million pounds annually (Sykes and Lehman 1957; 

 Chittenden 1974). White et al. (1969) tagging 

 studies suggested that in recent years the fishing 

 rate was probably 20%. 



The larger runs in the Delaware River in the 

 early 1960's appear to have been primarily based 

 upon one large year class except in 1963, when two 

 large year classes were involved. Because few 

 age-classes and only one year class support the run 

 each year, Delaware River American shad stocks 

 have little buffering against fluctuations in abun- 

 dance due to adverse natural or man-made en- 

 vironmental factors. Large fluctuations, in fact, do 

 appear in the catch records of the Lewis Fishery 

 since 1925 (Chittenden 1974, fig. 3). The Lewis 

 Fishery records show large runs over a 1- or 2-yr 

 period intermixed with stable periods when the 

 run was of small magnitude. This is the pattern 

 which would be expected when the fishery is sup- 

 ported by one year class in which males tend to 

 enter the fishery a year before the females and 

 there are essentially no repeat spawners. 

 Therefore, it appears probable that sine 1925, at 

 least, larger runs in the Delaware River have been 

 based upon one large year class and essentially no 

 repeat spawners. 



ACKNOWLEDGMENTS 



For assistance in the field collections, I am 

 deeply grateful to James Westman, James Hoff, 

 John Harakal, Don Riemer, James Barker, Frank 

 Bolton, Richard Coluntuno, Kenneth Compton, 

 Richard Gross, Charles Masser, Robert Stewart, 

 John Miletich, Sherman Hoyt, Leonard Schulman, 

 John Musick, Michael Bender, James Gift, Charles 

 Townsend, Ronald Bogaczk, and Kenneth Mar- 

 cellus of or formerly of Rutgers University, or 

 New Jersey Division of Fish and Game. 



Fred and William Lewis, Jr. generously gave 

 permission to collect fish at the site of their fishery 

 at Lambertville and frequently provided assist- 

 ance in seining. 



Jess Malcolm, formerly of the U.S. Bureau of 

 Sport Fisheries and Wildlife and of the Delaware 



River Basin Commission, provided information on 

 the composition of the 1961 run. The U.S. Bureau 

 of Sport Fisheries and Wildlife, New Jersey 

 Division of Fish and Game, Pennsylvania Fish 

 Commission, and New York Department of En- 

 vironmental Conservation kindly permitted use of 

 data collected during the Tri-state Surveys of the 

 Delaware River. Financial support was provided, 

 in part, by the Sport Fishing Institute, Delaware 

 River Basin Commission, and U.S. Public Health 

 Service. 



LITERATURE CITED 



Gating, J. P. 



1953. Determining age of Atlantic shad from their 

 scales. U.S. Fish Wildl. Serv., Fish. Bull. 54:187-199. 

 Chittenden, M. E., Jr. 



1969. Life history and ecology of the American shad, Alosa 

 sapidissima, in the Delaware River. Ph.D. Thesis, 

 Rutgers Univ., New Brunswick, N.J., 458 p. 

 1974. Trends in the abundance of American shad, Alosa 

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 Sci. 15:96-103. 

 Cochran, W. G. 



1953. Sampling techniques. John Wiley & Sons, Inc., N.Y., 

 330 p. 



Ellis, M. M., B. A. Westfall, D. K. Meyer, and W. S. Platner. 

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reference to shad migration. U.S. Fish Wildl. Serv., Spec. 



Sci. Rep. 38, 19 p. 

 Fredin, R. A. 



1954. Causes of fluctuations in abundance of Connecticut 

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Godwin, W. F. 



1968. The shad fishery of the Altamaha River, Georgia. Ga. 

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Godwin, W. F., and L. G. McBay. 



1967. Preliminary studies of the shad fishery of the Al- 

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 Hildebrand, S. F., and W. C. Schroeder. 



1928. Fishes of Chesapeake Bay. U.S. Bur. Fish., Bull. 

 43(l):l-366. 

 Howell, S. 



1837. Notice of the shad and shad fisheries of the river 

 Delaware. Am. J. Sci. Arts 32:134-140. 

 Judy, M. H. 



1961. Validity of age determination from scales of marked 

 American shad. U.S. Fish Wildl. Serv., Fish. Bull. 

 61:161-170. 

 La Pointe, D. F. 



1958. Age and growth of the American shad, from three 

 Atlantic coast rivers. Trans. Am. Fish. Soc. 87:139-150. 

 Leach, G. C. 



1925. Artificial progagation of shad. Rep. U.S. Comm. Fish. 

 1924. Append. 8:459-486. (Doc. 981.) 

 Leggett, W. C. 



1969. A study of the reproductive potential of the American 

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 the possible effects of natural or man induced changes in 



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