382 
BULLETIN OF BUREAU OF FISHERIES 
be expected in most uncontaminated fresh-water streams and lakes; and with the 
observations of Powers (1921 and 1929); and of Juday, Fred, and Wilson (1924). 
Experimental tests have demonstrated that many species of fresh-water fishes 
have a great tolerance for variations in hydrogen-ion concentrations over a wide 
range. Creaser (1930) showed brook trout to have a voluntary toleration of liydro- 
gen-ion concentrations from pH 4.6 to pH 9.5. Brown and Jewell (1926) found catfish 
and perch living in apparently good condition in a bog lake, the water of which ranged 
from pH 4.4 to pH 6.4; and also in a glacial lake nearby, the water of which varied 
N. RIO GRANDE 
P. COLUMBIA RIVER SYSTEM 
44 STATIONS. 153 DETERMINATIONS 
3.9 ' 4.3 ' 4.7 ' 5.1 1 5.5 1 5.9 1 6.3 1 3.7 1 
4.2 4.8 5.0 5.4 5.8 6.2 6-6 7.0 
4.2 4.6 5.0 5.4 5.8 6.2 6.6 7.0 7.4 7.8 8.2 8.6 9.0 
Figure 14. — Continuation of comparisons of pH values, stippled graph A figure 11, being the standard. 
7.5 ' 7.9 ' 8.3 ' 8.7 
7.8 a 2 8.6 9.0 
from pH 8.2 to pH 8.7. These workers demonstrated that the fishes from the two 
lakes survived transfer from either lake to the other. Wiebe (1931a) reports goldfish 
survive rapid changes from pH 7.2 to pH 9.6; largemouth black bass, from pH 6.1 to 
pH 9.5; smallmouth black bass, from pH 6.6 to pH 9.3; and sunfish from pH 7.2 to 
pH 9.6. Powers (1930) in reviewing the problem summarizes the existing data by 
saying that aquatic organisms are able to withstand a wide range in pH. The writer 
has confirmed this statement with gammarids, daphnia, unionids, and planaria, as 
well as for goldfish, perch, and catfish, in connection with pollution tests. 
It might seem, therefore, from both the field data and laboratory findings that 
the pH values of stream water would be of little consequence in pollution studies and 
in determining standards of water suitability. Plowever, the pH of natural water is 
