in July of different years and held for only 1.5 hours. Of 71 occur- 
rences of temperatures between 61° and 66°, all occurred during June, 
July,or August; 5 in June, 36 in July, and 30 in August. Duration of 
these temperatures was short, averaging 3.7 hours. Longest duration 
of any temperature over 60° was only 6.5 hours. 
Table 8.--Maximum and minimum water temperatures recorded and duration* 
Stream > Max. = puration * Month * Min- : puration * Month 
ECM Pee : soe CMP ene : 
F° hours Ee hours 
Maybeso Creek 64.0 Unknown July 32 4 May 
Harris River 64.0 ! Aug. 36 27 Dec. 
Indian Creek 66.0 IS July 30 VE May 
Old Tom Creek 66.0 HES) July 32 144 Jan. & 
* Harris River based on short period. In 1954, temperatures of 32° F. 
occurred in January, February, and March. 
Minimum Fresh Water Tempe ratures_l6/ 
Hatching of salmon eggs is directly related to accumulated temperatures 
in the streambeds. A certain number of temperature unitsl// are re- 
quired for the eggs to hatch, and for the hatched fry to work up to the 
surface of the gravel. In a controlled experiment with steelhead trout, 
Shapovalov (17) found the eggs required 563.0 to 585.5 temperature units 
to maximum hatch and 1074.6 to 1206.1 temperature units to maximum 
emergence from gravel. Temperatures below certain limits cause low 
survival. Abnormally low stream temperatures which occur early in the 
incubation period of the pink salmon may damage the developing eggs, 
particularly between the sixth and tenth weeks (9). 
The lowest mean monthly water temperature recorded for any stream was 
33.4° F. A mean monthly value of 31.4° F. was recorded in 1951 on Indian 
Creek, but this average was based on ai. incomplete month. The lowest 
temperature recorded on any stream was 30° F. and occurred several times. 
The longest duration of this temperature was 11 hours. Temperatures of 
32° occurred several times and held for periods as long as six days. 
Temperatures of 33° were common and persisted for periods up to ll days. 
A layer of ice 6 to 12 inches thick may form during extended periods of 
cold weather, but the streams usually continue to flow under this ice 
layer. 
16/ Winter water temperature records are not complete. 1953 is the 
only complete year covering all months. 
17/ One temperature unit (t.u.) equals 1° F. above 32° for a period of 
24 hours (17). fe 
