Table 1. — Depth, bottom type, and number of live mollusks 

 collected at stations in dredged canals in Boca Ciega Bay, 

 Fla., 1963-64 



South Florida * and the U.S. National Museum. 

 Specimens from this study were deposited in the 

 invertebrate reference collection of the BCF 

 (Bureau of Commercial Fisheries) Biological 

 Laboratory, St. Petersburg Beach, Fla. 



MOLLUSK-SEDIMENT RELATIONS 



Comparison of mollusks and bottom types 



showed that species and individuals were much 



less numerous in soft sediments of canals than in 



sandy sediments in undredged areas of Boca Ciega 



Bay (tables 1 and 2). Canal sediments, which 



averaged 85 percent silt and clay, had 16 live Tablk f.-Depth, bottom type and ""'"^f «/f'''«.'"«""f; 

 = ' , ^. . •'.' 11 i J collected at stations m undredged areas of Boca Ciega Bay, 



mollusks m 14 samples. Living specimens collected pi^,^ 1963~64 



at the seven canal stations were the gastropods 



Nassarius inbex and Haminoea antillanim, and the 



pelecypods Brachidontes exustus, Anoinalocardia 



cuneimens, and Mercenaria campechiensis. These 



species and 151 others were collected live from the 



24 stations in undredged areas of the bay. Sedi- 

 ments from natural bottom, which averaged 91 



percent sand and shell, yielded 5,631 live mollusks 



in 93 samples. 



Pratt (1953) suggested that soft sediments and 



associated hydrological conditions may be limiting 



because (1) rapid deposition has a smothering 



effect, (2) high organic content of soft sediments 



depletes dissolved oxygen, and (3) weak currents 



in areas of deposition are insufficient for the re- 

 moval of toxic metabolic wastes. Comparisons of 



sediments and environmental factors (Taylor and 



Saloman, 1968) in dredged and undredged areas at 



sampling stations lead us to conclude that the soft 



sediment is the principal factor luniting the abun- LITERATURE CITED 



dance and diversity of benthic mollusks in bayfiU 



canals of Boca Ciega Bay. Such sediments are as Abbott, R. Tuckeb. >t . ^ n„ 



*i • 1 A • i tu f A .^A^^A 1 1; 1954. American seashells. D. Van Nostrand Co., 



tliick as 4 m. in waterways that were dredged 15 Princeton, N.J., 541 pp. 



years ago. 1963 geashells of North America. Golden Press, 



N.Y., 280 pp. 

 Clench, William J. (Editor). 



1941-69. Monographs of the marine mollusks of the 

 Western Atlantic. Johnsonia, vols. I-IV. Dep. 

 Mollusks, Mus. Comp. Zool., Harvard Univ., 

 Cambridge, Mass. 

 Draqovich, Alexander, and John A. Kelly, Jr. 



1964. Ecological observations of macro-inverte- 

 brates in Tampa Bay, Florida, 1961-1962. Bull. 

 Mar. Sci. Gulf Carib. 14: 74-102. 

 GooDELL, H. G., and D. S. Gorsline. 



1961. A sedimentologic study of Tampa Bay, 

 Florida. Rep. Int. Geol. Congr., 21 Sess., Pt. 23, 

 pp. 75-88. Int. Ass. Sediment., Copenhagen, 1961. 



ACKNOWLEDGMENTS 



The authors gratefully acknowledge confirma- 

 tions and corrections of identifications made by 

 Harry W. Wells, Department of Biology, Univer- 

 sity of Delaware, Newark, Del. ; Joseph Rosewater, 

 Division of Mollusks, U.S. National Museum, 

 Washington, D.C. ; and George Radwin, San Diego 

 Natural History Museum, San Diego, Calif. 



• HiUnian Collection, University of South Florida, Tampa, Fla. 33620. 



302 



U.S. FISH AND WILDLIFE SERVICE 



