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Fishery Bulletin 104(3) 



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Figure 4 



Comparison of day and night temperatures recorded hourly by data storage tags on 

 Atlantic salmon iSalmo salar) postsmolts for selected periods of time. Night is shown 

 in grey and day is shown in white. Solid lines are the DST temperatures; the dashed 

 line represents freshwater temperature and dotted line represents sea temperature 

 at 8 m. The periods A to F are shown on Figure 3 for each tag. 



consequence for an individual fish, as well as be an 

 important factor controlling year-class strength and 

 abundance at the population level (McCormick and 

 Saunders, 1987, McCormick et al., 1998). The trans- 

 formation process from freshwater to salt water made 

 by smolts is accompanied by changes in metabolic rate 

 (Hoar, 1988) and increases in energy demands, which 

 explain the need for the fish to immediately begin feed- 

 ing. Levings (1994) concluded that of all the variables 

 influencing survival of postsmolt salmon, temperature 



is particularly important. If they are to survive, indi- 

 viduals must quickly adapt to their new physical envi- 

 ronment and be able to flee predators and seek prey. In 

 spite of its presumed importance, the ecology of salmon 

 smolts as they enter the marine environment is largely 

 unknown. This article provides the first recorded results 

 of temperatures experienced by salmon smolts as they 

 enter the sea and provides insight into how postsmolts 

 adapt to life at sea based on ambient temperature ranges 

 and temperature choices made by the postsmolts. The 



