288 Roosevelt Wild Life Bulletin 



F., but began to die at 84.2 degrees (mortality 20 per cent). None 

 died the following day, July 4, at 82.4 degrees ; but on July 5 at a 

 temperature of 83.2 degrees F., the mortality was 100 per cent." 

 Concerning the experiments Embody says : " It must be understood 

 that the foregoing rates do not prove that all strains of brook trout 

 will stand a temperature of 80 degrees F., and above. Undoubtedly, 

 there is much variation in this respect just as we find great varia- 

 tion in the rate of growth, in the behavior of trout to current and 

 light, and variation in power of resistance to disease germs. 



" Nor may we assume that brook trout will thrive in any pond or 

 stream whose temperatures do not exceed these uppermost limits. 

 Waters vary greatly in oxygen and carbon dioxide content, and these 

 gases may be present in insufficient amounts in one case or too great 

 amounts in the other to permit trout to live even in the low tempera- 

 tures of the average trout hatchery. 



" So far as temperature alone is concerned, however, it is the 

 writer's opinion that we have been a little too conservative and that 

 we shall have to revise to some extent our notions as to the mean- 

 ing of the terms, warm water and cold water." 



In the discussion of Embody 's paper at the meeting of the Ameri- 

 can Fisheries Society, the comments which were more or less adverse 

 to the higher temperature limit, largely pertained to hatchery 

 experiences. But Mr. G. C. Leach, head of the Division of Fish 

 Culture of the Federal Bureau of Fisheries, suggested that the 

 volume of water is one of the determining factors as concerns the 

 temperature-withstanding ability of trout. 



Again Embody ('22, pp. 7-8) says that the views which he quotes 

 concerning the temperature safety limits, were made prior to 1880, 

 when the trout brooks possibly were colder than they are today, 

 and continues : " There is a possibility that through natural selection 

 our speckled brook trout is gradually adapting itself to warmer 

 waters. According to present day evidence either this must be true 

 or certain statements of Ainsworth and Green were not based upon 

 complete observation. For upon an examination of the temperature 

 data from certain trout brooks in this county, we find a number 

 of instances where speckled trout apparently thrive and take the 

 hook in waters whose highest temperature ranges from 74 degrees 

 to 79 degrees F. The highest temperature in which speckled trout 

 were found was 81 degrees F. This was in the upper Van Pelt 

 Brook where three specimens were clearly observed apparently not 

 inconvenienced by the high temperature. 



" In other parts of this stream, brook trout were observed in 

 temperatures of 76°, 78° and 79° F. In the Dusenbury stream they 

 were seen in temperatures of 79° and 80° F. 



" It must be kept in mind that the temperatures referred to were 

 taken on the hottest days of the summer of 1918 when the maximum 

 air temperature in the open ranged from 95° to 100° F. Thus they 

 probably represent the extreme conditions occurring in these 

 streams. In order to find out the fluctuations in water temperatures, 

 a series of readings were taken in a warm, unshaded part of the 



