METHODS 



We examined the results from eight graduate student master's theses prepared at Louisiana 

 State University by Burleigh (1966), Weaver (1969), Wengert (1972), Spiller (1974), Hoar (1975), 

 Larrick (1975), Carney (1977), and Olinde (1977) and combined them with the related field studies 

 of Chabreck and Hoffpauir (1962), Herke (1971, 1977), and Chabreck et al. (1979). Fishery 

 aspects were not examined because Herke (1971, 1977, 1979) and Herke et al. (1987; also see 

 Herke et al. in this proceedings) have reviewed them extensively. We divided our analyses into 

 the effect of weirs on water quality, soils, vegetation, and animals. 



The study sites are shown in Figure 1 and the basic study results are outlined in Table 1. Four 

 study sites in coastal Louisiana were used by these investigators to study the effects of weirs. The 

 most extensively studied site is at Marsh Island, near the terminus of the Atchafalaya River. Other 

 sites are in Terrebonne, Barataria Bay, and at the Biloxi Marsh Public Shooting Grounds bordering 

 Lake Borne. Some investigators studied marshes as clusters with or without weirs, averaged the 

 data for each cluster, and then made comparisons of each cluster. Other studies measured 

 parameters inside a weired marsh and just outside. Many additional data were collected besides 

 those discussed here (Table 2). The only data on fish and invertebrates appear in the reviewed 

 scientific literature, and the only data on aquatic vegetation and overwintering waterfowl appear 

 in the unreviewed proceedings of conferences or symposiums. We found no contradictions between 

 our observations and summaries and those in the student theses or with conclusions based on these 

 theses appearing in symposia. The quotation of these theses in marsh management permit 

 applications are, however, often different from our and the students' observations. The value of 

 this review, therefore, is to illuminate and summarize the diverse and generally sparsely used data 

 in these student theses. 



Salinity values of marshes with and without weirs were calculated as cluster averages. Individual 

 marsh measurements are also reported if salinity was measured just inside and outside of the weir. 

 A histogram count of frequency versus salinity differences was then computed to discern the range 

 of differences resulting from weirs, and whether or not the differences were skewed toward higher 

 or lower salinities in weired marshes. 



In addition to the above summaries, we examined the formation of new ponds in the Biloxi 

 Marsh Public Shooting Grounds between 1955 and 1978. The geographical information system 

 at the Louisiana Department of Natural Resources, Coastal Management Section was used to 

 generate maps of various parameters, including, ponds 0-20 ha in size. The ponds appearing on 

 1955 and 1978 7V2-minute quadrangle maps were identified inside and outside the shooting grounds. 

 The shooting grounds constitute about one-quarter of the marsh within the quadrangle maps. 



RESULTS 



Table 2 is a summary of the various results mentioned in the papers consulted. Here we discuss 

 results in terms of water quality, soil conditions, vegetation, and animal usage. 



Water Quality 



Salinity comparisons were common. Salinities ranged from to 23 ppt, and the salinity 

 differences between marshes with and without weirs were inconsistent. Sometimes the salinity 

 behind weirs was higher and sometimes lower than in nearby marshes or in water bodies in control 

 areas. A comparison of salinities in marshes with and without weirs is shown in Figure 2. In 



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