Biological Survey — Oswego Watershed 



19 



brook trout may sometimes endure slightly higher ones. In the 

 case of brown and rainbow trout the highest suitable stream 

 temperature is believed to be close to 80° Fahr. 



In assigning any one of these three species to a stream it is 

 important to know whether the water temperature will exceed 

 cither of these points during the summer months. Hot days 

 were too infrequent during the past summer to permit one to 

 secure through actual observation, maxima in more than a few 

 streams. It was thus necessary to estimate them by means of 

 a table. Table 1 was used throughout the greater part of the 

 territory covered with one exception to be noted. 



Table 1. — Relation of Air and Water Temperatures in Trout Streams 



Max. air temp. deg. Fahr 



Max. water temp., Brook trout. . . 

 ,„- , (Brown trout. . 



Max. water temp. ^ Rainbow trout 



80.0 

 65.0 



82.0 

 66.5 



84.0 

 68.0 



86.0 

 70.0 



88.0 

 71.5 



90.0 

 73.0 



92.0 

 74.0 



69.0 



70.5 



72.0 



73.5 



75.0 



76.5 



78.0 



94.0 

 75.0 



79.0 



Checking up on the accuracy of this table in as many warm 

 streams as were found to contain trout there was found but slight 

 error in regions below 1,000 feet elevation, but in the higher 

 forested area particularly about the headwaters of Fish creek 

 (Lewis county) with elevations from 1,600 to 1,900 feet, the error 

 was large, noticeably however, on the safe side. That is, the water 

 temperatures corresponding to certain air temperatures as taken 

 in these streams were several degrees higher than in Table 1, for 

 brook trout. 



Two outstanding examples of this were the upper East Branch 

 of Fish creek and its tributary, Alder creek. Both streams were 

 densely populated with brook trout and showed the temperature 

 relations in Table 2. 



Table 2 — Relation of Water Temperature to Air Temperature in Fish 

 and Alder Creeks, Lewis County, N. Y. 





FISH CREEK 







section 



Air 

 temperature 



Water 

 temperature 



Atmospheric 

 condition 



Hour 



Date 



Upper 



Lower 



80 

 81 



68 

 68 



Bright 



Bright 



10:30 a. m. . 

 4:30 p. m.. . 



Aug. 1 

 Aug. 1 



A.LDER CREEK 





80 

 80 



69 



Bright 



Bright 



12:05 p.m... 

 12:00 p. m. . 



July 28 

 July 28 



Middle 



71 





Comparing Tables 1 and 2, it is evident that in the latter, the 

 water temperatures are from three to six degrees too high for the 



