266 



CiHislal & Marine Ecosystems — Our Lniiii^ Resources 



Geese 



Diving ducks 



Dabbling ducks 



Swans 



Sea/river ducks 



Year 



Fig. 4. Trends in waterfowl abun- 

 dance in the Chesapeake Bay, 

 based on 5-year running means, 

 1959-93, 



Table. Trends for waterfowl in 

 Chesapeake Bay, based on 5-year 

 running means from 1959 to 1993 

 (USFWS. Chesapeake Bay Field 

 Office. Annapolis. Maryland, 

 unpublished data). 



American Shad 



Like striped bass, American shad have 

 declined in Chesapeake Bay in recent decades; 

 unlike the stripers, this species has not shown a 

 strongly positive population response despite 

 moratoria on fishing in Maryland and Virginia. 

 Long-term trends show a drastic decline in fish- 

 ery landings to the point of almost total disap- 

 pearance in the bay (National Marine Fisheries 

 Service. Annapolis. Maryland, unpublished 

 data; Fig. 3d), This decline has been related to 

 blockages of spawning streams by dams, over- 

 harvest, and pollution (Blankenship 1993), 

 Population estimates in 1992 and 1993 for the 

 upper bay. where shad are counted during their 

 upstream migration to the Susquehanna River. 

 show a reversal of a recent positive trend, for 

 reasons yet unknown. 



Waterfowl 



Midwinter surveys estimate an average of 

 more than one million waterfowl along the 

 Atlantic Flyway winter in Chesapeake Bay each 

 year (USFWS. Chesapeake Bay Field Office. 

 Annapolis. Maryland, unpublished data). Of the 

 28 species of ducks, geese, and swans repre- 

 sented in this total, some are declining in abun- 

 dance, whereas others show increasing or vari- 

 able trends in abundance (Fig. 4; Table). In gen- 

 eral, duck numbers declined and goose popula- 

 tions increased since the late 1950"s as sub- 

 mersed aquatic vegetation and other duck foods 

 dwindled and changing farming practices left 

 more grain in fields for geese. Recently, geese 



have also declined as excessive harvest and poor 

 production on northern breeding grounds 

 reduced their numbers. Their distribution along 

 the Atlantic Flyway has also shifted to the 

 north. Mallards (Aiui.s plcityiiiynclms) and intro- 

 duced mute swans {Cygniis olor) have shown 

 moderate increases, but many other species, 

 including American black duck [Anas 

 nihripes). wigeon {A. awehvaiui), northern pin- 

 tail (A, acuta), canvasback (Aythya valisiiwria). 

 and redhead {A. aiiiericaiia). have declined or 

 stabilized at population levels substantially 

 lower than in the 195()'s, 



References 



Anderson. R.R., and R,T. Macomber, 1980, Distribution of 

 submerged vascular plants, Chesapeake Bay. Maryland. 

 Environmental Protection Agency. Chesapeake Bay 

 Prograin, Annapolis. MD. 126 pp. 



Blankenship, K. 1994. Bay bounces back from record-set- 

 ting spring "freshet." Bay Journal M 10): 1, 7. 



Blankenship. K. 1993. Biologists puzzled by sudden decline 

 of East Coast shad. Bay Journal 3(9): 1. 6. 



Chesapeake Bay Implementation Committee. 1988. The 

 Chesapeake Bay Program: a commitment renewed. U.S. 

 Environmental Protection Agency. Chesapeake Bay 

 Program Office. .Annapolis, MD, 88 pp. 



Chesapeake Bay Prograin. 1993. Environmental indicators; 

 measunng our progress, U.S, Environmental Protection 

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 MD. 



Dahl. T,E. 1 990. Wetlands losses in the United States 1 780's 

 to I980's. U.S. Department of the Interior. Fish and 

 Wildlife Service. Washington. DC. 21 pp. 



FIciiier. D.A.. G. Mackiernan. W. Nehlsen. and V. Tippe. 

 1983. Chesapeake Bay: a profile of environmental 

 change. U.S. Environmental Protection Agency. 

 Chesapeake Bay Program Office. Annapolis. MD. 200 

 pp. 



Gibson, M,R, 1993. Historical estimates of fishing monali- 

 ty on the Chesapeake Bay striped bass stock using sepa- 

 rable virtual population analysis applied to market class 

 catch data. Report to the Atlantic States Marine Fisheries 

 Commission Striped Bass Technical Committee. AtlanUc 

 States Marine Fisheries Commission. Washington. DC. 

 20 pp. 



Kennedy, V,S. 1991, Eastern oyster. Pages 3-1 to 3-20 in 

 Habitat requirements for Chesapeake Bay living 

 resources, 2nd ed. Living Resources Subcommittee, 

 Chesapeake Bay Program. U.S. Fish and Wildlife 

 Service. Annapolis. MD. 



Lipcius, R.M.. and W.A. Van Engel. 1990. Blue crab popu- 

 lation dynamics in Chesapeake Bay: variation in abun- 

 dance (York River. 1972-1988) and stock-recruit func- 

 tions. Bull, of Marine Science 46:180-194. 



Orth. R.J., and K.A. Moore. 1983, Chesapeake Bay: an 

 unprecedented decline in submerged aquatic vegetation. 

 Science 222:51-53. 



Orth. R.J., J.F. Nowak. G.F Anderson, and J.R. Whiting. 

 1993. Distribution of submerged aquatic vegetation in 

 the Chesapeake Bay and tributaries and Chincoteague 

 Bay — 1992. U.S. Environmental Protection Agency. 

 Chesapeake Bay Program Office. Annapolis. MD. 161 

 pp. 



Orth. R.J.. J. Simons, R. Allaire. V. Carter. L. Hindman. K. 

 Moore, and N. Rybick. 1985. Distribution of submerged 

 aquatic vegetation in the Chesapeake Bay and tribu- 

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