to the larger tidal creeks. Spaced 

 35 to 7C m (115 to 230 ft) apart, the 

 shallow, narrow ditches were designed 

 to remove pools and standing water 

 from the marsh and thereby prevent the 

 breeding of mosquitoes. Ditching as a 

 method of mosquito control appears to 

 have begun in New Jersey at the turn 

 of the century (Smith 1902, 1907), but 

 it was practiced most widely during 

 the Depression years of the 1930 's 

 with support from the Works Progress 

 Administration and the Civilian 

 Conservation Corps. This attempt at 

 "managing" the marshes was so thorough 

 that by 1938 almost 90% of the tidal 

 wetlands between Maine and Virginia 

 had been ditched (Bourn and Cottan 

 1950), 



The ecological impact of such a 

 widespread alteration of the marshes 

 is surprisingly difficult to describe 

 with any certainty (Daiber 1974). 

 Much of the early literature appears 

 to be based on casual impressions and 

 anecdotal information and often 

 reflects the biases of "mosquito 

 controllers" or conservationists. The 

 findings of a widely cited study of 

 ditching effects in a Delaware marsh 

 by Bourn and Cottam (1950) may have 

 been influenced by dredging in a 

 nearby river (Lesser et al. 1976). 



Information is lacking about the 

 effects of ditching on New England 

 high marsh; most of the work on this 

 problem has been done in Delaware 

 and New Jersey, though one of the 

 better early studies on the effect 

 of ditching on shorebirds and water- 

 fowl was carried out in the Duxbury, 

 Massachusetts, marshes (Bradbury 

 1938). In Duxbury, the marshes had 

 supported abundant and diverse 

 waterfowl before mosquito control 

 operations were completed, but after 

 ditching, the marshes became "dry 

 and devoid of birds" (Daiber 1974). 



Ditching can enhance the growth 

 of high marsh plants at the expense of 



53 



Spartina alterniflora , although the 

 tall creek-bank S^. alterniflora often 

 grows along the banks of the ditches 

 if the spoil from ditch construction 

 has not been left there. Where S^. 

 alterniflora does develop, the nesting 

 and production of clapper rails 

 ( Rallus longirostris ) may be enhanced 

 (Stewart 1951; Ferrigno 1966; Shisler 

 and Shulze 1976). Where spoil is 

 deposited, high marsh grasses or woody 

 vegetation such as Iva fructescens and 

 Baccharis 



hali mi folia 



become 



established (Miller and Egler 1950; 

 Daiber 1974). These species are 

 generally of low value, but some birds 

 (e.g. boat-tailed grackle, Cassidix 

 mexicanus ; red-winged blackbird, 

 Agelaius phoeniceus ) may use them for 

 nesting (Meanley and Webb 1963; Post 

 1974). Because the ditches are often 

 dug to drain pond holes and other 

 shallow depressions, submerged aquatic 

 plants such as Ruppia are usually 

 eliminated. The loss of these plants 

 as well as the protected open water 

 makes the marsh less attractive to 

 waterfowl and other birds. 



Bradbury's (1938) study of the 

 Duxbury marshes suggests that many of 

 these changes can be reversed. Daiber 

 (1974) summarized it in his review as 

 follows: 



"The technique of restoration 

 was based on the premise that 

 mosquito larvae would be eaten by 

 Fundulus hetero cl itus . the 

 mummichog minnow. The job was to 

 create a habitat where fish could 

 live at low tides and high 

 temperatures. Former potholes 

 were restored by damming outlets 

 with sod. Care was taken to keep 

 the water level about nine inches 

 below the marsh surface, thus, 

 keeping it free of water. Some 

 potholes were deepened to assure 

 sufficient water for Fundulus 

 to live in during dry periods. 

 Controlled burning of salt 

 hay made a variety of insects 



