Fishes of the Western Nortli Atla7itic 



469 



Table II. Percentage Composition of Smolt Population Based on Years Spent as 



Parr in Fresh Water 



North America 



Penobscot R., Maine {Sf) 



Pollett R., Petitcodiac R. system, 



N.B.(4J:3) 



Margaree R., N. S. {12) 



Miramichi R. system, N.B. (^j: i). 



Miramichi R., N.B. (jp) 



Grand Cascapedia R., Que. {2(^ . . . 



Moisie R., Que. {io4)* 



Six west coast rivers of Newfound- 

 land (jj) 



East coast rivers of Newfoundland, 



including Labrador (20) 



Greenland (5j) 



Europe 



Avon R., Hampshire, Eng. (JOO) . . . 



Shannon R., Eire {136, I3i)\ 



Scotland (JOo) 



Rivers of southern Scotland {lod) ■ ■ 



Tweed R., Scotland (joo) 



Norway - Kristiansund distr. (J5)tt 

 Trondhem district (J5)tt • • • • 

 East Finmarken (J5) 1909 .... 

 Repperfjord R.** 



* Average 1923 and 1924 collections, 

 tt Average 190S and 1909. 



have barely attained the required lo-cm size at the right time will, if slow growing, 

 make small smolts, perhaps only 12 cm long. But Elson has clearly pointed out that 

 this hypothesis "definitely does not specify that young Atlantic salmon become smolts 

 as soon as they reach a length of i o cm, but rather that they transform after reaching 

 this length in the smolt-running season immediately following." 



Smolt lengths have been reported to be as follows, south to north : rivers tributary 

 to the Gulf of Maine, ^-6 inches (18); average for the rivers of Canada, 5-7 inches; 

 the Little Codroy River, Newfoundland, 5-9 inches; George River, Ungava Bay, 

 8.5 inches (115). 



Only a small percentage of the numerous alevins that are hatched survives 

 the freshwater stage as parr to become smolts and go to sea, nor is this astonishing 

 when all the dangers that threaten their continued existence are taken into account: 

 predators, competitors, disease, food shortage, abnormal water temperatures, and others. 

 For discussion of survival at different stages, see Length of Life (p. 479). 



Downstream movements of smolts result from a change in their behavior asso- 

 ciated with the physiological changes involved in smoltification. According to Hunts- 

 man, when they assume the smolt condition they tend to leave the bottom, come nearer 



