^\, 



Figure 7. In the last 20 years more than seven 

 percent of the Nation's important estuarine 

 area has been lost, principally to housing de- 

 velopment. (U.S. Bureau of Sport Fisheries and 

 Wildlife photo by Richard Stone) 



contaminated by pollution. Since an estimated 83 

 per cent of estuarine marshlands has been elimi- 

 nated in San Francisco Bay, one may calculate at 

 least an equal loss of oyster bottom, or about 

 825,000 acres. In 1936, 6^A million pounds of Bay 

 shrimp were harvested, but only 10,000 pounds in 

 1966. Softshell clams have vanished from the Bay. 



At the peak of the Connecticut shellfish indus- 

 try in 1900, approximately 27,000 acres of marsh- 

 land existed.^ ^ Today only approximately 9,000 

 acres remain and the rate of loss is alarming. In 

 Fairfield County alone between 1954 and 1964, 

 933 acres of marshland or 45 per cent of the 

 marshland that existed in 1954 were destroyed by 

 development. Of Fairfield County's remaining 

 1,100 acres of marshland, only approximately 100 

 acres is assured as a wildlife preserve. Thirty per 

 cent of the shellfish grounds in Connecticut 

 presently are closed by the State Health Depart- 

 ment because of poor water quality. 



Mosquito control projects have devastating side 

 effects on fish and other aquatic life. Although 

 DDT and other insecticide pollutants are the most 

 dramatic killers, there are other damaging control 

 activities. 



Drying marshes by cutting drainage ditches is a 

 popular method of preventing mosquitoes from 

 breeding. This has complicated effects in relation 



Report of J. Richard Nelson, Chairman, Connecticut 

 Shellfish Commission to Subcommittee on Fisheries and 

 Wildlife Conservation of the House Merchant Marine and 

 Fisheries Committee, March 1967. Other statistics in this 

 paragraph also come from this report. 



to aquatic life. Ditches at sea level can be 

 beneficial by providing entry to the marsh for fish, 

 by allowing better irrigation of the marsh by tidal 

 action, and by facilitating passage of nutrients out 

 of the marsh to the bay. Impounding marshes with 

 dikes or levees to prevent mosquito breeding tends 

 to make fresh water lagoons of the marshes and to 

 eliminate them as places which can support marine 

 and brackish-water Hfe. 



Here the conflict of public interests requires a 

 balancing of the value of marine fish resources 

 against the nuisance of mosquitoes. Furthermore, 

 diking proposals also may involve balancing bene- 

 fits to marine fish resources against benefits to 

 waterfowl and fresh water fish resources, since 

 current waterfowl improvement techniques often 

 involve diking off salt water areas to create fresh 

 water impoundments. 



V. MODIFICATION AND DIVERSION OF 

 FLOW 



Coastal engineering projects such as harbor 

 charmels, power plant and flood control diversions 

 can affect the circulation, flushing and mixing 

 dynamics of coastal or adjacent waters. 



Estuarine waters usually are low in salinity, 

 with salt water from the sea continually being 

 diluted with fresh water from rivers. This dilution 

 sets up a pattern of decreasing salinity from the 

 ocean, up through the bays and into the tidal 

 rivers. Since the whole variety of estuarine life is 

 adjusted to salinity patterns, changing them can 

 have disruptive effects. 



Many human activities affect the quantity of 

 fresh water inflow, its temporal distribution, and 

 contents. River flow can be reduced, especially by 

 diversion for cities, for irrigation of agricultural 

 land, and by intentional or accidental use of 

 spillways or breaks in levees. 



Conversely, flow is increased in the basins 

 receiving the diversion. Frequently, increased total 

 output is the result of denuding the watershed by 

 removing vegetation and by other activities that 

 decrease absorption and subsurface retention. In- 

 crease in runoff is especially vivid in paved urban 

 areas and along highways where as much as 30 

 acres per mile is paved or carefully sloped to 

 maximize runoff.^ ^ As a consequence, there is 



C. E. Renn, "Man as a Factor in the Coastal 

 Environment," Transactions of North American Wildlife 

 Conference, 1956. 



111-39 



