LABORATORY PROCEDURES 



Plankton samples were placed in enameled 

 photographic trays. Seaweeds and jelly fishes 

 were removed from the samples manually, and 

 the remaining volume was determined in the 

 laboratory by the displacement method de- 

 scribed by Thrailkill (1957). Plankton counts 

 were made from aliquots whenever the wet 

 plankton volume of the sample exceeded 0.5 ml. 

 After the sample had been diluted to a known 

 volume, usually 500 ml, four 5-ml. aliquots 

 were withdrawn with a calibrated pipette. 

 They were then transferred into a quadripar- 

 titioned petri dish for examination and count- 

 ing under a binocular dissecting microscope. 

 Samples having a wet volume of 0.5 ml. or less 

 were transferred directly to petri di.shes for 

 counting. All samples were examined routinely 

 for unusual organisms that might have been 

 excluded from the aliquots. The mean number 

 of organisms per cubic meter of water was 

 calculated for each taxonomic group. 



Body lengths of chaetognaths and fish larvae 

 were measured-chaetognaths from the anterior 

 extermity of the head to the tip of the caudal 

 segment, excluding the caudal fin (Owre, 

 1960), and fish larvae from the snout to the 

 base of the hypural plate (standard length). 



ENVIRONMENTAL FACTORS 

 HYDROLOGY 



The minimum and maximum water tempera- 

 tures observed were 12.8° and 32.0° C. The 

 smallest range in temperature at individual 

 stations occurred in Boca Ciega Bay (15.3° 

 C), and the greatest (18.4° C.) in Old Tampa 

 Bay (table 3). Seasonally, the range in mean 

 temperatures between stations located on a 

 traverse from offshore to Hillsborough Bay 

 (.stations 1, 2, 3, 4, 9, 10, 13. 14) was greatest 

 in the spring (3.9° C.) and lowest in the win- 

 ter (1.0° C). These ranges in the fall and 

 summer were 1.7° and 1.2° C. respectively. 



Salinity was determined by Mohr-Knudsen 

 method (Knudsen, 1901). Lowest salinities 

 were usually in the upper area of Hillsborough 

 Bay and highest 18.5 km. (10 nautical miles) 

 offshore (table 3). The seasonal differences in 

 mean salinities between these two areas (sta- 

 tions 1 and 14) were 8.62 p.p.t. (fall), 6.75 

 p.p.t. (winter), 8.03 p.p.t. (spring), and 13.58 

 p.p.t. (summer). The range in salinity at in- 

 dividual stations decreased progressively from 

 upper Hillsborough Bay seaward. The smallest 

 range was 18.5 km. offshore and the greatest in 

 upper Hillsborough Bay, where temporal 

 changes in salinity generally followed the dis- 



Table S.—Mean surface water temperature and saliniti/ for Tampa Bay and the adjacent Gulf of Mexico. September 1961 through 



August 1962 



212 



U.S. FISH AND WILIFE SERVICE 



