Reddin et al : Diurnal and nocturnal temperatures for Salmo solar 



417 



54"N 



52°N 



50°N 



48'N 



46°N 



58 W 



56 W 



54-W 



52 W 



Figure 1 



Map of Newfoundland. Labrador, and Quebec showing the release loca- 

 tion at Campbellton River for Atlantic salmon {Salmo salar) smolts with 

 data storage tags attached. 



with a precision of ±1°C and an accuracy of 0.15°C. The 

 iB4 data storage tag will store up to 2048 readings but 

 the number of data recorded by each tag depends on the 

 length of time that the tag was at large and the sampling 

 rate of the tag. Our iB4 tags were set to start on the day 

 of tagging and record a temperature every hour — a sam- 

 pling rate that would allow for 85 days of temperature 

 recordings. Tags were calibrated by the manufacturer 

 and checked for accuracy on return. A tag weighs 5.5 g 

 in air and less than 2.6 g in water, is approximately 24 

 mm by 17 mm by 8 mm, and has a hole at either end for 

 attachment to a fish. Tag programming, data acquisition, 

 and data downloading were achieved by the user with a 

 connecting clamp interfaced to the serial adapter on any 

 standard IBM compatible computer. No correction for 

 drift in the time function was made because of the short 

 period over which the experiment took place (Walker et 

 al., 2000; Reddin et al., 2004). Tags were attached to 

 salmon smolts by using a double-wire (0.32 mm stainless 

 steelj bridal that was passed through the dorsal muscu- 

 lature and that was anchored to the fish by m.eans of a 

 backing plate on the opposite side of the fish. A reward 

 of $10 Canadian was offered for the return of the tag. 

 The smolts were anaesthetized with clove oil, tagged, 

 and placed in holding tanks in the river and given an 

 approximate 10-hour recovery period before release in 

 the evening on the downstream side of the counting 



fence. All smolts survived the tagging process. From 311 

 salmon tagged and released, 15 DSTs were recovered 

 with data intact. All tagged fish were recovered during 

 the year of tagging. 



Data analysis 



Temperature data recorded by the recovered DSTs were 

 analyzed and compared to oceanographic and freshwa- 

 ter temperature data collected during the summer of 

 2002. The freshwater data was recorded by a Hugrun 

 temperature recorder (Hugrun, Sidumuli 13, Reykjavik 

 108, Iceland) placed in the trap at the Campbellton 

 River counting fence, and the sea temperatures came 

 from Hugrun recorders placed just outside the estuary 

 of Campbellton River at 8 m depth and from another 

 at Comfort Cove at 10 m, both reported by Colbourne^'* 

 (Fig. 1). Periods of daylight and darkness were esti- 

 mated from the U.S. Navy Observatory^'^ online photo- 

 period calculator. Latitudinal and longitudinal positions 



^* Colbourne, E. 2003. Physical oceanographic conditions 

 on the Newfoundland and Labrador Shelves during 2002. 

 DFO, CSAS Res. Doc. 200.3/020, .57 p. 



'^ U. S. Naval Observatory, Astronomical Observations 

 Department. 2004. Website: http://aa.usno.navy.mil/ 

 data/docs/RS_OneDay.html [accessed on 7 March 2006.] 



