Figure 7. — Central Boca Ciega Bay near Treasure Island Causeway in 1963 showing bayfill areas ( photograph 



courtesy of Airflite, St. Petersburg, Fla.)- 



was recorded near shore at Mullet Key on Janu- 

 ary 31, 1966 (Saloman and Taylor, 1968). 



Water temperature is usually the same in the 

 open bay and in baytill canals, except in winter 

 when periodic cold fronts create a temporary 

 thermocline in deep water. At such times, bottom 

 water may be 4 to 5° C. warmer than surface 

 water and serves as a refuge for polythermal fishes 

 (Kinne, 1963). If cold weather persists for more 

 than a few days, however, bottom water becomes 

 cold and sequestered fishes may die. During pro- 

 longed cold in February 1966, John PI. Finucane 

 (unpublished data)' observed mass mortality 



among snook, Centro-panvus undeci?n-al.is (Block), 

 in bayfill canals of Boca Ciega Bay. 



Average salinity in Boca Ciega Bay (32 p.p.t.) 

 approaches that of the nearshore Gulf and is at 

 least 10 p.p.t. higher than water in northern 

 reaches of Old Tampa Bay and Hillsborough Bay 

 (table 3). Even though the major 2:)ortion of an- 

 nual rainfall (127 cm.) comes in the summer and 

 fall, seasonal fiuctuations of salinity in the lagoon 

 are slight. Appreciable changes occur only in sur- 

 face water directly south of Lake Seminole Dam 



" Uiipublislit'd (hitu I quarterly report) on file, Bureau of 

 Coininercial Fisheries Itiologioal Laboratory, St. Petersburg 

 Beach. Fla. 33706. 



KFFECTS OF HYDKAILIC DREDGING AXD COASTAL DEVELOPMENT IN BOCA CIEGA BAY, FLA. 



221 



