Fnedland et al . Growth patterns in postsmolts of Salmo solar 



473 



a large oceanic region by their first summer 

 at sea (Holm et al., 1996; Shelton et al., 

 1997). These distribution patterns suggest 

 that postsmolts migrate to the northwest 

 and may be less likely to use inshore ner- 

 itic habitats. However, in the Northwest 

 Atlantic, the few recovery data available for 

 postsmolts suggest differing views of which 

 habitats represent the nursery area for 

 postsmolts. Salmon postsmolts have been 

 reported to use estuarine waters; therefore 

 it is possible that they possess specific be- 

 haviors to orient themselves to inshore ar- 

 eas during their first year at sea ( Robitaille 

 et al., 1986; Dutil and Coutu, 1988; Cunjak 

 et al., 1989). In contrast, postsmolts have 

 also been collected from research surveys 

 in the Labrador Sea and indirectly from bird 

 colonies, providing e\idence that the extent 

 of the postsmolt migration includes waters 

 north of Newfoundland ( Montevecchi et al., 

 1988; Reddin and Short, 1991). Recoveries of 

 postsmolts in estuarine areas support the 

 hypothesis that specific habitats serve as 

 nursery areas for postsmolts, whereas recov- 

 eries in the pelagic zone support the alterna- 

 tive, that juveniles have thei'mal preferences similar 

 to adults and do not use specific postsmolt nursery 

 areas. 



In this paper we re-examined material collected 

 by Dutil and Coutu (1988) with the aim of under- 

 standing the use of the Gulf of St. Lawrence by 

 salmon postsmolts. Specifically, we collected circuli 

 spacing data from salmon scales to address the fol- 

 lowing questions: 1) Are postsmolts retained in the 

 Gulf of St. Lawrence during the postsmolt growth 

 season or are they transient in the area?; and 2) Do 

 postsmolts recovered in the Gulf exhibit growth pat- 

 terns similar to postsmolts from other stocks? The 

 answers to these questions will hopefully allow us to 

 make some inference about the nature of the nurs- 

 ery for Atlantic salmon and salmonids in general. 



Figure 1 



Map of Northwest Atlantic area showing postsmolt habitat for stocks in 

 the Gulf of St. Lawrence and south (horizontal hatchingi and sampling 

 area for Gulf of St. Lawrence postsmolts (vertical hatching). 



Material and methods 



We collected scale circuli spacing data representa- 

 tive of postsmolt gi'owth for juvenile salmon captured 

 in the Gulf of St. Lawrence and for thi'ee index stocks 

 froin the southern portion of the range of salmon in 

 North America. Gulf of St. Lawrence postsmolt 

 salmon were collected in 1982-84 and were originally 

 reported in Dutil and Coutu ( 1988 ). These postsmolts 

 were captured in experimental gill nets along the 

 northwest shore of the Gulf during the months from 



August to October (Fig. 1). Data for comparative 

 purposes come from the returning adults of hatch- 

 ery origin fish from the Connecticut, Penobscot, and 

 Saint John rivers, all located south of the Gulf of St. 

 Lawrence (Fig. 1). Data for the Connecticut and 

 Penobscot rivers have been presented earlier (Fried- 

 land et al., 1996b); whereas, the Saint John data are 

 newly reported here. Sample sizes sorted by smolt 

 year of migration to sea and age of maturity are re- 

 ported in Table 1. The low number of ISW returns to 

 the Connecticut River did not provide sufficient 

 samples for inclusion in our study. 



