navigation channels, mainline Mississippi River levees, and upstreann diversions and flood 

 control reservoirs have virtually eliminated overbank flooding along the lower Mississippi 

 River. Consequently, most of the riverborne sediments ore being transported past 

 formerly active deltas and into the deeper Gulf of Mexico (Gagliano and van Beek 

 1970). This loss of sediment input has, except in Atchafalaya Bay, prevented large-scale 

 delta building, and has accelerated subsidence and erosion of existing marshes. Other 

 human causes of wetland loss include canal dredging and associated spoil disposal and 

 drainage of wetlands for agricultural purposes (Gagliano 1973). Gagliano (1973) 

 attributed approximately 25% of the total land loss in coastal Louisiana during the 

 previous 30 years to oil and gas industry dredging. 



Saltwater intrusion, another major cause of wetland deterioration, is occurring in 

 many areas of the LCR. Saltwater intrusion has wide-ranging adverse effects, such as 

 allowing encroachment of the predaceous southern oyster drill (Thais haemastoma ) onto 

 productive oyster reefs and conversion of fresher marshes to more saline types or to open 

 water. 



FISH AND WILDLIFE IMPLICATIONS OF WETLAND DETERIORATION 



Fisheries 



The marshes of the LCR are extremely important to the maintenance of its 

 estuarine-dependent sport and commerical fisheries. These wetlands produce vast 

 amounts of organic detritus, an important trophic component of estuarine fish and 

 shellfish productivity. The marshes and associated shallow waters of the LCR are also 

 important as nursery habitat for many estuarine-dependent species. This importance has 

 been documented by numerous authors, such as Herke (1971), White and Boudreaux 

 (1977), Rogers (1979), and Chambers (1980). There is growing evidence that the amount 

 of marsh is the most important factor influencing estuarine-dependent fishery 

 production. Turner (1979) reported that Louisiana's commercial inshore shrimp catch is 

 directly proportional to the area of intertidal vegetation, and that the area of estuarine 

 water does not seem to be directly associated with shrimp yields. He further noted that 

 the loss of wetlands in Louisiana has a direct negative effect on fisheries. Although the 

 effects are masked by large annual variations in yield, wetland losses in the LCR 

 reported by Craig et al. (1979) are equivalent to 2.86 million km^ (6.31 million lb) of 

 shrimp harvest "lost" over the past 20 years (Turner 1979). Lindall et al. (1972) presented 

 evidence that shrimp and menhaden are being harvested at or near maximum substainable 

 yield. These species accounted for nearly 99 percent of the total volume of Louisiana's 

 commerical fish and shellfish landings in 1976. Further evidence that this is occurring 

 was presented by Harris (1973), who noted that any substantial decreases in marsh 

 habitat will result in decreased estuarine-dependent fishery production. An analysis of 

 the dependence of menhaden catch on wetlands in the LCR was conducted by Cavit 

 (1979). The findings of this analysis suggest that menhaden yields are greatest in those 

 LCR estuarine basins having the highest ratio of marsh to open water. Based on the 

 evidence cited above, continued wetland loss in the LCR could lead to serious declines in 

 its estuarine-dependent fishery. 



Wildlife 



Wildlife dependent on the LCR marshes face serious habitat declines as a result of 

 future land loss and saltwater intrusion. Losses of fresh to intermediate marsh or 



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