not tolerant to it, saltwater intrusion at present is probably not the major cause of land loss. 

 Walker et al. (1987) give their tentative ranking of nine causes of this loss. In order of decreasing 

 importance, the first four are (1) change in the depositional site and stage in the delta cycle; (2) 

 compaction and localized differential subsidence; (3) sea-level change and long-term climatic change; 

 and (4) human modification of the Mississippi River system. They do not list saltwater intrusion 

 per se, but their text indicates it is a result of canal dredging (cause 5) and fluid extraction (cause 

 8). 



Some (for example, Turner 1987) would place canal dredging and its accompanying levee 

 construction higher on the list. There are publications (and general agreement) showing that 

 these result in direct and indirect destruction of marsh; any disagreement on this matter is about 

 the degree of the latter. Thus, no matter what the net effect of semi-impoundment on marsh loss, 

 it always results in some marsh destruction. Moreover, unless the water-control structures are 

 maintained, they become non-functional and any possible benefits from them are lost. Even so, 

 the direct and indirect marsh loss caused by the canals and levees remains indefinite. 



MARICULTURE 



Mariculture is the raising of marine organisms under captive or controlled conditions. The 

 United States now imports more shrimp than is caught domestically, and much of this imported 

 shrimp is from mariculture in tropical and subtropical areas, mostly in "Third World" countries. 

 Fortunes have been made there where labor is cheap, growing seasons are long, and the need for 

 foreign exchange seems more urgent than protection of the environment. But these profits have 

 come at a high environmental cost. 



Most mariculture has occurred in coastal zones, resulting in large-scale destruction of the 

 mangroves. Mangrove areas are generally regarded to be important nursery and feeding grounds 

 for wild fishery species (see, for example, Cortiguerra 1979; Prince Jeyaseelan and Krishnamurthy 

 1980; Ong 1982; and Camilleri and Ribi 1986). As such, mangrove areas are an ecological 

 counterpart to Louisiana's coastal marshes. Fortunately, there is growing concern around the globe 

 over the loss of mangroves, and scientists and governments are calling for or requiring measures 

 to protect the mangrove areas (see, for example, Cortiguerra 1979 (the Phillipines); Ong 1982 

 (Malaysia); Soegiarto 1984 (Indonesia); and Snedaker et al. 1986 (Ecuador)). 



A few years ago a new Cajun-style dish called "blackened redfish" was an immediate and 

 phenomenal success. It soon appeared on restaurant menus across the United States. As a result, 

 demand for redfish and the dockside price of the fish soared. The fishing pressure put on the wild 

 stocks was sufficient to raise fears that the population would be overfished. Some saw mariculture 

 of redfish as a means to reduce pressure on the wild stock; others saw it as a source of public 

 benefits such as increased employment; and still others saw it as a means to make huge profits 

 as has been done by some Third World mariculturists. In 1987 the Louisiana legislature passed 

 two bills authorizing use of the coastal marsh for mariculture. They were subsequently signed by 

 then Governor Edwin Edwards and became Acts 305 and 386. Both acts indicated that a 

 reasonable number of fish were to be released to the wild; both required that the mariculture 

 operations take place within an area having a marsh management plan; and both allowed the 

 Department of Wildlife and Fisheries to exempt the mariculturist from any limitations on how the 

 organisms could be harvested. Act 305 authorized the issuance of up to 10 permits, good for 5 

 years, and not to encompass over 3,238 ha each; required all fishery organisms used in a project 

 to be purchased from a legal source; and contained a number of guidelines to be followed. Act 

 386 contained none of these restrictions. We discuss these acts further in the following paragraphs. 



The release of hatchery-reared fish into the wild poses a threat to the wild stocks. The hatchery 

 fish have very little genetic variability. Introduction of the genes of hatchery-reared fish into the 

 wild gene pool will eventually diminish the capacity of wild fish to survive adverse environmental 



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