blue crabs and oysters is another 

 potential reason for the high nega- 

 tive correlation, since blue crabs 

 are known to prey on oysters (Menzel 

 et al. 1966). The results of Meeter 

 and associates appear counter to the 

 observation of Menzel and associates 

 that oyster mortalities at given lo- 

 cations in Apalachicola Bay rise as 

 salinity rises following dry weather 

 conditions. Boynton (1975) proposed 

 that salinity fluctuations rather 

 than some optimum salinity provide 

 the most favorable conditions for 

 oysters. The study by Menzel et al. 

 (1966) indicates that there are oys- 

 ter enemies at both ends of the sa- 

 linity spectrum, blue crabs being one 

 example of an oyster predator that is 

 favored by low salinities. Fluctua- 

 ting salinity should inhibit preda- 

 tion/parasitism on oysters from both 

 directions . 



Apalachicola Bay is an example 

 of an estuary receiving runoff from 

 a dammed river. Cattle ranching and 

 forest management activities, such as 

 clearcutting, ditching, diking, and 

 road construction also have affected 

 freshwater inputs. Studies have been 

 made of the long-term and short-term 

 dynamics of chemical and biological 

 factors in the bay and the effects of 

 watershed alterations. Using spec- 

 tral analysis, Meeter et al. (1979) 

 determined that damming the upriver 

 systems has thus far not substan- 

 tially altered long-term river flow 

 patterns but has affected short-term 

 flow patterns, particularly during 

 periods of low flow. Storage behind 

 the dam is small relative to the flow 

 of the river, and therefore the dam 

 has had little impact on the pattern 

 of flow (Boynton 1975) . 



Lowered water quality has re- 

 sulted from the cattle and forestry 

 operations. Effects of the forestry 

 operations in Tate's Hell Swamp are 



particularly well documented (Living- 

 ston and Duncan 1979). Each aspect 

 of the operations tended to increase 

 the rate of response of local runoff 

 to rainfall, which increased the am- 

 plitude and decreased the duration of 

 runoff events, causing more abrupt 

 than normal changes in salinity and 

 nutrients in the vicinity of the 

 swamp drainage. Sudden increases in 

 water color and decreases in both 

 dissolved oxygen and pH in upper por- 

 tions of the bay were associated with 

 periods of high runoff from the al- 

 tered swamp. These periods coincid- 

 ed with periods when the upper bay 

 ordinarily is heavily utilized as a 

 nursery ground by fish and inverte- 

 brates. Reduced water quality from 

 runoff from clearcut areas signifi- 

 cantly reduced the number and bio- 

 mass of white shrimp, the dominant 

 invertebrate, in upper portions of 

 the bay. Dissolved oxygen and pH 

 levels increased in clearcut areas 

 of the swamp after regrowth of a 

 covering vegetation, suggesting that 

 swamp vegetation has an ameliorating 

 effect on these water-quality factors 

 (Livingston and Duncan 1979). 



MISSISSIPPI RIVER 



Referred to as "the fertile 

 crescent" (Gunter 1963) , the coast- 

 al area dominated by the effluent of 

 the Mississsippi River is one of the 

 most productive fishery systems in 

 the world. The three-state coastal 

 area of Louisiana, Mississippi, and 

 Alabama, with less than 4 percent of 

 the Nation's coastline, produced al- 

 most 35 percent of U.S. marine coast- 

 al landings in 1978 (National Marine 

 Fisheries Service 1979). Most of 

 the estuarine area associated with 

 the Mississippi River lies in the 

 State of Louisiana, where extensive 

 studies relating fishery production 



411 



