4 
BULLETIN OF THE BUBEAU OF FISHEBIES 
The chemical data in the following records were all obtained by Dr. Minna 
Jewell. The first of the tests in the summer of 1921 was at Station A on August 5, 
when the following data were secured: 
Depth 
37J feet 
40 reet 
42i feet 
45 feet 
47J feet 
50 feet 
Temperature, °F 
70.6 
68 
63 
59.5 
55.6 
53.6 
Oxygen, c. c. per liter 
4. 24 
2.35 
0.95 
0.09 
0 
0 
pH 
7. 8 
7. 5 
7.3 
7. 2 
7 
7 
Fish in cages placed at 38 and 40J feet remained in good condition until the 
end of the test, several hours later. All of the fish of each of two different sets, 
including perch, minnows, and mud minnows, died within two hours when put ia 
cages placed at 43 and 45 i feet. One week later the thermocline was somewhat 
deeper, as shown by the following data: 
August 12, 1921, Station A 
Depth 
40 feet 
42J feet 
45 feet 
47i feet 
50 feet 
52J feet 
Temperature, °F... j 
68.5 
68 
65.4 
58.3 
54.9 
52.6 
O.xygen, c. c. per liter 
5. 47 
5 
1. 7 
0.96 
0 
0 
pH- 
8.4 
8 
7. 3 
7 
6.9 
At 3.08 p. m. about 15 perch (yoimg of the year) were put in each of the cages 
and placed at 42, 44|, 47, and 49| feet. At 4.23 p. m. all of those in the two 
lower cages Were dead and aU of those in the two upper cages were in good condition 
except one that had died in the uppermost cage. Those left in the two upper cages 
were in good condition when examined again at 7 p. m. At 7.45 a. m. of the follow- 
ing day 9 fish were in good condition at 42 feet and 8 at 44^ feet. At 1.45 p. m. 
only 4 were living at 42 feet and 1 at 44 J feet. A test made August 16 and 17 
gave data similar to others and need not be described. 
Another depression of the thermocline is shown by the following data: 
August 19, 1921, Station A 
Depth 
45 feet 
47'J feet 
50 feet 
52i feet 
66. 2 
3.6 
8. 1 
63 
1. 84 
7.4 
54. 9 
.59 
7.0 
53.8 
.42 
6.9 
pH 
The above records were made at 6.30 a. m., and at 8.15 a. m. fish were placed 
in three cages at the following depths: In a cage at 45 feet were four perch, a log 
perch, and a young smallmouth black bass. These had already been in the cage 
at that depth for two days and still seemed in good condition. A cage containing 
