CONCERNING HIGH WATER TEMPERATURES AND TROUT 



By G. C. Embody 

 Cornell University, Ithaca, New York. 



We often use the terms "warm" and "cold" water as an indica- 

 tion of the suitability of streams and lakes for various kinds of fish. 

 These of course are only relative in meaning, and the question nat- 

 urally arises as to what temperature we should take as the dividing 

 line between warm and cold waters. We speak of such forms as 

 the various trout, salmon, and whitefish as cold-water forms be- 

 cause they live and grow at a normal rate, and reproduce in waters 

 of comparatively low temperature. On the other hand, we con- 

 sider yellow perch, bass, sunfish, and bullheads warm-water forms 

 because their life activities take place best in warmer waters. The 

 latter forms will live and often reproduce in a temperature suitable 

 for trout, but it has been generally believed that they will not grow 

 at a normal rate in so-called cold waters. 



From a perusal of the literature on the subject of fish culture, 

 the impression came upon me that temperatures of 68° and 70° F., 

 were generally regarded as near the dividing line between cold and 

 warm water, these temperatures having been used possibly more 

 often than others, as the maxima for brook trout water. 



The following notes are offered, merely upon the supposition that 

 the above impression is correct. They are based upon many tem- 

 perature readings taken in streams of Tompkins County, New York, 

 and in the experimental fish hatchery of Cornell University. The 

 records include readings taken on the hottest summer days of the 

 last three or four years. In saying, hottest summer days, reference 

 is had to those days during which the air temperatures ranged from 

 90° to 101° F. 



Let us refer at first to an experiment carried on in one of the 

 ponds on the fish hatchery grounds. This pond was 50 by 150 feet 

 and had a maximum depth of 4 feet. It received water from a 

 creek in which temperatures as high as 83° F., had been taken in 

 previous years and was thus considered a warm water pond. In 

 June, 1920, 225 small fingerlings equally divided between brook, 

 brown, and steelhead trout were planted. There were also added 

 eight 3-year-old goldfish which spawned several times, and about 

 200 young bullheads at the swarming age. The water temperatures 

 ranged between 69° and 81.5° F., during July and August. There 



