FISHERY BULLETIN: VOL. 85, NO. 1 



also common. In low-energy areas, estuarine sys- 

 tems with large amounts of suspended sediments 

 and high turbidities frequently have fine sediments 

 (Guilcher 1967; Folger 1972). Submerged vegeta- 

 tion, shown to offer many crustaceans protection 

 from predators (Nelson 1979; Stoner 1979; Coen et 

 al. 1981; Heck and Thoman 1981), is associated with 

 estuarine areas of low turbidity (Zieman 1982; 

 Thayer et al. 1984), and these beds of submerged 

 vegetation also reduce turbidity (Short and Short 

 1984) and alter sediment characteristics (Thayer et 

 al. 1984). Determining the protective value of any 

 suite of environmental characteristics, therefore, 

 may be quite complex. 



Turbidity and sediment characteristics, however, 

 appear to be important factors governing predation 

 rates on juvenile brown shrimp, and anthropogenic 

 modifications of estuarine systems that influence 

 these characteristics may affect shrimp survival. 

 Turbidity levels and patterns of sediment deposition 

 in estuaries are mainly influenced by riverine inputs, 

 tidal properties, and wave action (Postma 1967; 

 Davis 1983), although biological processes are also 

 important (Haven and Morales-Alamo 1972; Biggs 

 and Howell 1984). Modifications of estuarine sys- 

 tems through dredging, channelization, and altera- 

 tion of freshwater inflows, therefore, can impact 

 predator-prey relationships, and such effects should 

 be addressed in evaluating these activities. 



ACKNOWLEDGMENTS 



We thank the Director E. Klima and staff of the 

 National Marine Fisheries Service, Southeast Fish- 

 eries Center Laboratory in Galveston for support- 

 ing this research. In particular, C. Albrecht and M. 

 de Diego are acknowledged for their experimental 

 work on Atlantic croaker and red drum. K. N. 

 Baxter provided needed field personnel and equip- 

 ment; G. Zamora, Jr., D. Boss, and D. Emiliani aided 

 in the collection of experimental organisms; and C. 

 Caillouet, T. Williams, and W. Browning provided 

 much of the experimental equipment. H. Wynn of 

 Texas Industrial Minerals Company donated the 

 kaolinite. K. Gilligan, W. Kittrell, and the staff of 

 the Texas Parks and Wildlife Department and F. 

 Schlicht and W. Baker of Houston Lighting and 

 Power Co. aided in the collection of red drum. J. 

 Matis and D. Colby offered statistical advice, and 



C. Coleman conducted the particle size analyses. 

 Suggestions for improving the manuscript were pro- 

 vided by Z. Zein-Eldin, E. Klima, S. Ray, D. Aldrich, 

 G. Matthews, and N. Rabalais. B. Richardson and 



D. Patlan helped prepare the final draft. 



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