Reddin et al Diurnal and nocturnal temperatures for Salmo solar 



419 



Thermal ecology 



A comparison of temperatures for night and day for the 

 two tag recoveries with detailed data indicated differ- 

 ences between daily night and day temperatures for 

 weeks 24 to 29 (11 June-22 July) (Fig. 5). The tagged 

 salmon appeared to be at lower temperatures during 

 the day than at night. Although there were only slight 

 differences between day and night for the cumulative 



temperatures in some weeks (i.e., week 24 [11-17 June]), 

 for others the differences were quite large (i.e., week 27). 

 These differences were reflected in the overall mean of 

 12.5°C at night compared to the overall mean of 11.6°C 

 during the day — values which are significantly different 

 from each other it =-6.32, P<0.0001) and which possibly 

 reflect temperatures at different depths. Although there 

 was some variation among fish, this pattern was gener- 



