VARIATION IN DEPTH AT WHICH FISH CAN LIVE 
3 
At Station B, August 3 at 10.35 a. m., four wire cages were placed at 40, 49, 
55, and 65 foot levels. Each contained some minnows, perch, and a young small- 
mouth black bass. The cages were examined at 1.45 p. m., and it was found that 
all of the fish in the two upper cages were living while those in the two lower cages 
were all dead. Late in the afternoon of the same day, with the aid of Doctor 
Welch, records of temperatures were made and water samples taken from the 49 
and 55 foot levels. The temperature at 49 feet was 62^°; at 55 feet, 51.6°; and at 
65 feet, 50°. The oxygen content at 49 feet was 5.28 c. c. per liter and at 55 feet 
2.6 c. c. At 49 feet pH was 7.6, and at 55 feet 7.1. These data indicated that 
the lowest limit at which fish could live was somewhere in the thermocline. 
Tests made August 6 at Station A, in connection with class work, indicated 
that fish could not live at as gi-eat a depth as at Station B, and also that the thermo- 
cline was not as far down. In the afternoon of the following day, with the aid of 
Doctor Welch, who made the chemical examination, the following data were secured: 
August 7, 1920, Station A 
Depth 
45 feet 47i feet 50 feet 52J to 70 feet 
65.8 to 70.4 64 58 51.6 to 46.5 
5.52 to 7.29 4.33 2.28 0.028 to 0 
^_ 7.8 to 8.1 7.7 7.3 7.0 to 6.9 
I 
At 4.25 p. m. fish were placed in baskets at 37i, 42^, 47^, and 53i-foot levels. 
At 8.30 p. m. the fish in the two upper baskets were in good condition; some of 
those at 47 i feet were all right and some were ailing; all at 53 i feet were dead. 
During the two following days (August 8 and 9) the tests were continued, with some 
shifting of depths of the cages, with the general result that it was shown that fish 
lived very well at 45 feet; at 47 A- feet some would live for a day or more but not 
in good condition; and at 50 feet, or below, all soon died. A young sucker and a 
young bullhead were left at the 45-foot level until August 17, when they were still 
in good condition and were released. 
During August, 1921, tests were made at Station A on five different dates and 
at Station B on three dates. Two of these latter tests were unsatisfactory because 
of the continued high wind and rough water which subjected the buoys to which 
the cages were attached to constant motion. This presumably accounted for the 
death of most of the fishes in the upper cages, which, under normal conditions, 
should have lived. In the tests made in 1921 the cages were placed at 2J-foot 
intervals. Where slight discrepancies occur between the depths of the cages and 
the levels at which temperature and chemical records were made, they are due to 
the fact that on checking up the distances on the rope to which the baskets were 
attached and by taking for a standard the rope used in taking water samples for 
analysis such discrepancies were found to exist. Different ropes of varying texture 
and previous treatment often differ in the amount of change in length which they 
undergo when subjected to tension under water. 
Temperature, °F 
Oxygen, c.c. per liter. 
nH 
