480 



Fishery Bulletin 97(3), 1999 



the region (Dutil and Coutu, 1988). The northern Gulf 

 can cool to temperatures below 2°C by late Novem- 

 ber and to lethal temperatures later in winter, from 

 the surface to a depth of 100 m. Thus, the Gulf must 

 be viewed as a seasonally transient habitat for 

 postsmolts in most, if not all, years. 



Our comparisons of growth patterns could be en- 

 hanced with the inclusion of growth information from 

 stocks originating in the Gulf of St. Lawrence itself 

 We assumed that the range of growth patterns pro- 

 vided by the three comparison stocks is representa- 

 tive of stocks outside the Gulf region. However, the 

 samples failed to account for growth signals from wild 

 stocks and included only populations from the south- 

 ern portion of the range. However, the strength of the 

 sample is that it did include three stocks of varying 

 growth and survival characteristics, thus supporting 

 the contention that it likely represents a range of growth 

 responses similar to those occurring in wild stocks. 



A future challenge for research would be to char- 

 acterize the thermal properties and production char- 

 acteristics of the area potentially comprising the 

 postsmolt nursery to evaluate its spatial and tempo- 

 ral extent and annual variability. From these descrip- 

 tive analyses, it may be possible to design migration 

 simulations and field experiments that could begin 

 to describe the mechanisms that form the postsmolt 

 nursery and, in turn, it may be possible to develop 

 an understanding of the factors affecting postsmolt 

 survival and recruitment in salmonid populations. 



Acknowledgments 



We thank L. Marshall, Department of Fisheries and 

 Oceans, Halifax, for providing scale material from 

 the Mactaquac Hatchery and summary return rate 

 data, and J. Kocik and J. Boreman for reviewing early 

 drafts of the manuscript. 



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