Analyses have been made of the diatom populations from several areas in 

 Chocolate and Galveston Bays, Texas. The results of these analyses were com- 

 pared with the results of concurrent biological surveys. A chi-square test 

 indicated the Catherwood Diatometer developed random, reproducible samples of 

 diatoms. The drastic change in the shape of the diatom curve in polluted 

 environments was correlated with a similar change in the species diversity. 

 The structure of the diatom flora was the same as that previously found in 

 Chesapeake Bay, Maryland, under similar ecological and chemical conditions. 



72. HOPKINS, S.H., "Use of the Clam Rangia auneata as an Indicator of Eco- 

 logical Effects of Salinity Changes is Brackish Coastal Waters," Report 

 to the Office of the Chief of Engineers, U.S. Army, Corps of Engineers, 

 Washington D.C., Jan. 1973. 



The clam Rangia auneata lives in the low salinity brackish zone of tidal 

 rivers and bays from Maryland to Texas (and Mexico) . In this zone, where the 

 clam may make up 99 percent of the benthic biomass, it is a key species in the 

 ecosystem, converting algae and plant debris to meat used by many fishes, crus- 

 taceans, wild fowls and man. It is also an important commercial species worth 

 tens of millions of dollars annually for shell and meat. 



Because the clam requires variable salinity between 2 and 10 parts per 

 thousand for successful reproduction, it can be used as an indicator of salin- 

 ity and of the ecological effects of salinity changes. Measurements of a large 

 sample of the population will show whether recruitment is occurring, and how 

 often. The Corps' Mermenteau project in Louisiana is used as an example to 

 show how this information can be applied in the management of a coastal engi- 

 neering project. 



73. HUGHES, D.A., "Orientations of Migrating Pink Shrimp," National Geographia 

 Society Research Reports: 1966 Projects^ P.H. Oehser, ed.. National 

 Geographic Society, Washington, D.C., 1966, pp. 127-129. 



This study determines the movements of postlarvae and juvenile pink shrimp 

 within inshore waters where there are distinct ebbtides and floodtides. Flfeld 

 sampling indicates that postlarvae entering the estuaries are caught almost 

 exclusively in floodtides and juveniles leaving the estuaries are caught pre- 

 dominantly in ebbtides. The mechanism causing this discrimination between tides 

 and the utilization of the tides by the shrimp were examined. Early experiments 

 on this project yielded negative results when ♦•he "preference" of postlarvae for 

 waters of different salinity and ionic constitution was tested in a Y-maze situa- 

 tion. 



The behavior of postlarvae and juveniles was observed in the laboratory 

 within currents of water, the "quality" of which was altered during the experi- 

 ments. Preliminary results showed that salinity changes affect the levels of 

 activity and the direction of swimming with respect to the current of both 

 postlarvae and juveniles. 



74. HUGHES, D.A., "On the Mechanisms Underlying Tide-Associated Movements of 

 Penaeus duoranon (Burkenroad) , " Food and Agriculture Organization of the 

 United Nations, Fisheries Report, Vol. 3, No. 57, 1967, pp. 867-874. 



Postlarval shrimp move inshore in floodtides while juveniles move in ebb- 

 tides. This appears to be caused by the postlarvae and juveniles response to 



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