416 



Fishery Bulletin 104(3) 



O'Neil et al."; Anon.^). Many authors have noted that 

 information on the sea life of Atlantic salmon (Salmo 

 salar L.) may aid in our understanding of the recent 

 increased mortalities that occur at sea compared to 

 those experienced in the 1970s (Mills, 1989; Reddin 

 and Friedland, 1993; Dempson et al.^; Jacobsen, 2000; 

 Reddin et al., 2000). In the southern end of the range 

 of Atlantic salmon in North America, declines have 

 been so severe that some stocks are now threatened 

 with extinction and others are currently considered to 

 be extirpated (Marshall et a\}°). The recent listing of 

 seven salmon stocks in the State of Maine under the 

 U.S. Endangered Species Act and in rivers in the upper 

 Bay of Fundy further underscores the urgency to under- 

 stand more completely the entire salmon's life history, 

 including the period spent in the ocean. Although the 

 cause (or causes) is unknown, the continued declines in 

 abundance appear directly related to increased mortal- 

 ity at sea, perhaps from predation (DFO, 1998; Cairns 

 and Reddin"; O'Neil et al.'). 



New techniques have recently been applied to the 

 study of salmon in the sea on both sides of the North 

 American continent for Pacific and Atlantic salmon, and 

 recommendations have been made on their future use 

 (Boehlert, 1997; Anon'^). Although large scale experi- 

 ments with complex tags are attractive, the high cost 

 per tag and likelihood of low returns, in part due to 

 reduced commercial fishing for Atlantic salmon, have 

 indicated that a smaller scale experiment with inexpen- 

 sive simple tags may be the best place to start (Anon. 3). 

 Reddin et al. (2004) demonstrated that these tags when 

 applied to Atlantic salmon adults could provide insight 

 into some aspects of salmon life history. 



Overall, the objectives of the present study were 1) to 

 determine if DSTs could be applied to Atlantic salmon 

 smolts and if data could be successfully recovered, 2) to 



learn more about the thermal habitat of Atlantic salmon 

 during its early marine life, and 3) to test the hypoth- 

 esis of the commonly held assumption that salmon are 

 mainly surface or near to surface dwellers. This ar- 

 ticle describes the results of the migration of Atlantic 

 salmon smolts from Campbellton River, Newfoundland, 

 in relation to sea water temperatures recorded by DSTs 

 in 2002. 



Materials and methods 



Experimental site 



Atlantic salmon smolts, defined by Allan and Ritter 

 (1977) as juvenile salmon that are making the transi- 

 tion from freshwater to the marine environment, were 

 obtained in 2002 for tagging from an enumeration fence 

 on Campbellton River, Newfoundland (Fig. 1) where in 

 past years, high numbers were available in early spring 

 (Downton and Reddin'-). Also, because Campbellton 

 River has a counting fence that is suitable for obtain- 

 ing counts of adult salmon as they re-enter freshwater, 

 there was a strong possibility of recapturing a return- 

 ing tagged salmon so that its tag could be recovered 

 (Fig. 1). Smolt and adult salmon have been counted 

 at Campbellton River annually over the last 11 years 

 (O'Connell et al.''). In total, there were about 32,600 

 salmon smolts counted through the counting fence at 

 Campbellton River in 2002, and of these, 311 (-1% of 

 total smolts) were tagged and released with data stor- 

 age tags (DSTs). Owing to the size and weight of the 

 tags, only smolts over 20 cm fork length were selected 

 for application of tags. Average length of tagged smolts 

 was 25 cm compared to an average length of 18 cm for 

 untagged smolts. Larger smolts were also purposely 

 selected to increase probability of survival. 



' O'Neil, S., J. Ritter, and K. Robichaud-LeBlanc. 2000. Pro- 

 ceedings of a workshop on research strategies into the causes 

 of declining Atlantic salmon returns to North American 

 rivers. CSAS (Canadian Stock Assessment Secretariat), 

 Proceedings Series 2000/18, 80 p. Department of Fisher- 

 ies and Oceans, Government of Canada, 200 Kent Street, 

 Stn. 12032, Ottawa, Ontario, Canada KIA 0E6. 



8 Anon. 2003. Report of the Working Group on North Atlan- 

 tic Salmon. ICES Headquarters, Copenhagen, 31 Mareh-10 

 April 2003. ICES CM. (council meeting) 2003/ACFM: 19, 

 310 p. 



3 Dempson, J. B., D. G. Reddin, M. F. O'Connell, J. Helbig, 

 C. E. Bourgeois, C. C. Mullins, T. R. Porter, G. Lilly, J. 

 E.Carscadden, G. B. Stenson, and D. Kulka. 1998. Spatial 

 and temporal variation in Atlantic salmon abundance in the 

 Newfoundland-Labrador region with emphasis on factors 

 that may have contributed to low returns in 1997. DFO, 

 CSAS, Res. Doc. 98/114, 161 p. 



1" Marshall, T. L., G. J. Chaput, P. G. Amiro. D. K. Cairns. R. 

 A. Jones, S. F. O'Neil, and J. A. Ritter. 1999. Assessments 

 of Atlantic salmon stocks of the Maritimes Region, 1998. 

 DFO, CSAS Res. Doc. 99/25, 80 p. 



11 Cairns, D. K., and D. G. Reddin. 2000. The potential 

 impact of seal and seabird predation on North American 

 Atlantic salmon. DFO, CSAS Res. Doc. 2000/012, 36 p. 



Tags 



The data storage tags (DSTs), sometimes referred to as 

 archival tags, used in this study were iB-4 tags (Maxim/ 

 Dallas Semiconductor Corporation, Sunnyvale, CA) and 

 were repackaged for use on fish by Alpha Mach Devices 

 Inc. (Mont St-Hilaire, Quebec, Canada). The iB4 tags 

 are small microprocessor-based data loggers embedded 

 in green urethane on which is shown (at bottom right 

 corner of tag) a return address, an identifying number, 

 and the offer of a reward for return of the tag. The iB4 

 DST records temperature over a range of -5° to 26°C 



1- Downton. P. R.. and D. G. Reddin. 2004. Status of Atlan- 

 tic salmon (Salmo salar L.) in Campbellton River, Notre 

 Dame Bay (SFA 4), Newfoundland in 2003. DFO, CSAS 

 Res. Doc. 2004/043, 49 p. 



13 O'Connell, M. F., J. B. Dempson, C. C. Mullins, D. G. 

 Reddin, C. E. Bourgeois, T. R. Porter, N. M. Cochrane, 

 and D. Caines. 2003. Status of Atlantic salmon (Sa/nio 

 salar L.) stocks of insular Newfoundland (SFAs 3-14A), 

 2002. CSAS Res. Doc. 2003/002, 63 p. 



