Fishes of the JVestern North Atlantic 481 



males it suggests the possibility that males may live longer in the western Atlantic than 

 in the eastern Atlantic. 



Fourteen years is the greatest age reported for an Atlantic Salmon. A fish from 

 the Moisie River, Quebec, that had spawned in four consecutive seasons is reported 

 to have attained that age {28). Another Moisie River Salmon weighing 38.5 pounds, 

 which had also spawned four times, is reported to have been 1 3 years of age (xo j). 

 Menzies has also referred to a 13-year-old Scottish Atlantic Salmon (joo). All of these 

 very old fish were females. 



Tolerance to Temperature. It is evident, from their northerly range, that Atlantic 

 Salmon prefer cool waters, and from their observed behavior in streams, that water 

 temperature is certainly one of the most influential of environmental factors, as is illus- 

 trated in the two branches of the Margaree River (p. 475). Egg development, incu- 

 bation time, and the rate of growth of fry are definitely linked to temperature condi- 

 tions (p. 466). 



The lethal temperature for any given individual varies with its thermal history. 

 Experimental fingerlings that had been living at 2 5°C began to die when exposed 

 for any length of time to a temperature of 2 8.5°C; and planted fingerlings died when 

 the stream temperature reached 30.5° C (9<§). Parr tolerate temperatures as high as 

 28— 29.5° C (8 2-8 5° F), at least temporarily, but they die under experimental condi- 

 tions at temperatures of 32.9 and 33.8° C (90.2 and 9i.8°F). The older fish die when 

 the water temperature rises as high as 28-29.5° C, which happens in some of the 

 smaller streams of New Brunswick and in some of the rivers of outer Nova Scotia during 

 periods of very low water resulting from deficient rainfall and protracted hot weather 

 (65: 485; 67:476). 



The success or failure of commercial fishing and of angling is closely associated 

 with the temperature of the water, and it is common knowledge among anglers that 

 Atlantic Salmon do not rise freely to the fly if the water is warmer than about 70° F. 



Food. Studies of specimens from many parts of their range indicate that the same 

 items — May fly nymphs, caddis larvae, and particularly chironomid larvae — usually pre- 

 dominate in the food of parr; all live in the bottom. However, as the fish grow, surface 

 food assumes greater importance. Allen has given a comprehensive review ot the feeding 

 habits of young Atlantic Salmon (j: 47—76). 



Studies in eastern Canada have shown that chironomid larvae consitute the chief 

 food of parr that are beginning to feed (jjp: 499-506); later, especially during mid- 

 summer. May fly nymphs become important. Toward the end of the summer growing 

 season, caddis larvae are taken in increasing numbers. Some Plecoptera (stone flies) 

 as well as simulids and tipulids have been found in small or limited quantities in the 

 stomachs of parr examined in early summer and in the fall. 



The feeding by parr in the River Dee was found to be indiscriminate. A single 

 meal might include representatives of a dozen or more species taken at random from 

 under stones (insect larvae), in open water (Cladocera and small beetles), or from sur- 

 face driftage (aerial and terrestrial arthropods); the large number of dipteran flies 



