415 



Abstract — Data storage tags (DSTs) 

 were applied to Atlantic salmon (Salinn 

 salar L.) smolts during their seaward 

 migration in the spring of 2002 at a 

 fish counting fence on Campbellton 

 River, Newfoundland. Our objectives 

 were to discover whether or not salmon 

 smolts could carry DSTs and survive, 

 whether or not useful data on thermal 

 habitat could be obtained and inter- 

 preted, and whether or not salmon 

 smolts moved vertically in the water 

 column. Data were downloaded from 

 15 of the recovered tags and revealed 

 the hourly water temperatures expe- 

 rienced by the fish for periods of 3 to 

 71 days. The data on the DSTs were 

 analyzed for temperature patterns 

 in relation to migration behavior 

 and diurnal movement of the fish. 

 While in the sea, the DSTs recorded 

 night temperatures of 12.5°C, which 

 were higher than day temperatures 

 of 11.6'C; the record from moored 

 recorders, however, indicated that 

 sea temperatures actually declined 

 at night. It is hypothesized that posts- 

 molts avoid avian predators during 

 daylight hours by positioning them- 

 selves deeper in the water column and 

 that they were pursuing prey during 

 the deeper vertical descents or ascents 

 noted during the periods of more rapid 

 changes in temperature. 



Diurnal and nocturnal temperatures 



for Atlantic salmon postsmolts (Salmo salar L.) 



during their early marine life 



David G. Reddin' 



Peter Downton' 



Kevin D. Friedland^ 



' Science Branch, Department ol Fisheries and Oceans 

 80 East White Hills Road 

 P. O. Box 5667 



St. John's, Newfoundland Canada AlC 5X1 

 E-mail address (for D G Reddin) ReddinDe'dfo-mpo.gc ca) 



^ National Marine Fisheries Service 

 28 Tarzwell Drive 

 Narragansett, Rhode Island 02882 



Manuscript submitted 27 September 2004 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



28 September 2005 by the Scientific Editor 



Fish. Bull. 104:415-428 (2006). 



Our knowledge of the ecology of ma- 

 rine fish, and specifically salmon, at 

 sea has recently been enhanced by 

 information recovered from data stor- 

 age tags (DSTs) and tracking tags 

 (Sturlaugsson^; LaCroix and McCurdy, 

 1996; Wada and Ueno^; God0 and 

 Michalsen, 2000; Reddin et al., 2004). 

 Direct tracking, although valuable, 

 has a number of shortcomings, includ- 

 ing the usually short duration of 

 tracking because of the requirement 

 to follow the fish. This short-term 

 tracking often results in interrupted 

 data streams and the added concern 

 that the actual tagging may affect, 

 at least in the short term, the sub- 

 sequent behavior of the fish (LaCroix 

 and McCurdy, 1996; Walker et al., 

 2000). Studies of salmon at sea over 

 long periods require new tools and 

 several authors have noted that DSTs 

 are among the least expensive meth- 

 ods of answering some of the ques- 

 tions posed regarding the sea life of 

 salmon. Also, the near extirpation of 

 some stocks, particularly in the Inner 

 Bay of Fundy area of Canada and 

 Maine, U.S. A, requires an explana- 

 tion of the causative factors (Boehlert, 

 1997; Anon.*; Friedland et al., 2001; 

 Reddin et al., 2004). DSTs should be 

 able to provide better information on 

 the natural behavior of individual 

 fish, their specific habitats, and loca- 

 tion over the period of their residence 



in the sea because of the longer period 

 that information can be collected. 



On both sides of the North Atlan- 

 tic, attention has been recently fo- 

 cused on the downturn in Atlantic 

 salmon stocks and the potential cause 

 or causes (Nickson^; Mills"'; DFO*^; 



' Sturlaugsson, J. 1995. Migration study 

 on homing of Atlantic salmon iSalmo 

 salar L.I in coastal waters W-Iceland — 

 depth movements and sea temperatures 

 recorded at migration routes by data stor- 

 age tags. ICES CM. (council meeting) 

 1995/M: 17, 13 p. 



- Wada, K. and Y. Ueno. 1999. Homing 

 behavior of chum salmon determined by 

 an archival tag. NPAFC (North Pacific 

 Anadromous Fish Commission Doc. 425, 

 29 p. 



3 Anon. 1998. Report of the Study Group 

 on ocean salmon tagging experiments 

 with data logging tags. ICES CM. 

 (council meeting) 1998/G: 17, 34 p. 



 Nickson, Sir D. 1991. Chairman's 

 report, Atlantic Salmon Trust, progress 

 report, December 1991, 1 p. Atlantic 

 Salmon Trust, Moulin, Pitlochry, Perth- 

 shire, Scotland PH16 5JQ. 



■5 Mills, D. (ed.). 1996. Enhancement 

 of spring salmon. Proceedings of a one- 

 day conference held in the rooms of the 

 Linnean Society of London; 26 January 

 1996, 135 p. Atlantic Salmon Trust, 

 Moulin, Pitlochry, Perthshire PH16 5JQ 

 Scotland. 



^ DFO (Dept. of Fisheries and Oceans). 

 1998. Atlantic salmon abundance over- 

 view for 1997. DFO CSAS (Canadian 

 Stock Assessment Secretariat), Stock 

 Status Report D0-02(1998), 22 p. 



