FISHERY BULLETIN: VOL. 73, NO. 1 



Table 1. — Daytime measurements of temperature and salinity recorded during the hot season of 1973 from three creeks in the 



vicinity of the Northside Generating Station, Jacksonville, Fla. 



'Only one recording. 

 ^Not recorded. 



was 39.7°C taken at the outfall of Unit 2. The data 

 shown in Table 1 suggest that the thermal regime 

 present in Nichols Creek was somewhat inter- 

 mediate between that of the other two creeks. 

 However this is not entirely the case. During the 

 initial phase of each rising tide, tidal action causes 

 the injection of heated effluent from the power 

 plant up the entire length of Nichols Creek. On 19 

 September, we recorded this injection as it 

 reached and later passed Station 1 in this creek 

 (see Figure 2). The highest temperature recorded 

 at Station 1 during this day was 36.2°C. The pas- 

 sage time of this injection of hot water was approx- 

 imately 2 h with temperatures greater than 34°C 

 lasting approximately 1 h. Only a slight drop in 

 temperature was apparent when the hot water 

 reached Station 3 situated approximately 0.6 mile 

 away (see Figure 2). Hence, whereas the 

 minimum and average temperatures in Nichols 

 Creek are more similar to those of Browns Creek 

 than to those in San Carlos Creek, the maximum 

 temperatures in Nichols Creek are more similar to 

 those in San Carlos Creek. Consequently, at the 

 onset of each rising tide (twice daily), organisms 

 living in Nichols Creek are subjected to a period of 

 1- or 2-h duration during which the water temper- 

 ature is markedly above ambient and almost as 

 high as that in San Carlos Creek. 



Table 2 provides a list of the species of fishes 

 collected from the three creeks during the hot sea- 

 son of 1973. A total of 48 species belonging to 23 

 families were collected. Aside from the Cy- 

 prinodontidae and certain of the Gerreidae and 



o 



" 33.0 



a 



TIME OF DAY 



Figure 2. — Recordings of water temperature taken in Nichols 

 Creek on the initial stage of rising tide, 19 September 1973. 

 Appearance of thermal effluent from the power plant is indicated 

 by the sudden increases in temperature at Stations 1 and 3. 



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