Table 4. Number of ponds 0-20 ha in Biloxi Marsh in 1955 and 1978 and changes. 



Table 5. Percentage of vegetation in three areas with control and weired marshes (adapted from 

 Larrick 1975). 



fish and crustaceans will not be duplicated here, since this is the subject of a related paper 

 presented at this meeting (see Herke et al.). 



DISCUSSION 



The basic potential direct effect of weirs is to stabilize water levels. This stability leads to 

 longer periods of marsh flooding. Water quality is sometimes different behind weirs, compared to 

 water quality in unweired marshes. Submerged vegetation increases as a result of deeper flooding, 

 and overwintering waterfowl are attracted to either the increased water levels or submerged vegeta- 

 tion. Densities of resident animals are relatively unaffected by this type of water level management. 

 However, the long-term health of the marsh which animals including overwintering waterfowl 

 depend on may be seriously compromised if vegetation is as stressed as it appears to be. 



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