324 BULLETIN OF THE BUREAU OF FISHERIES. 
Perch Perch 
Hours submerged. Perch. | survive Hours submerged. Perch surviv- 
used. 5 used. Hi 
ing. ing. 
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It will be observed that some perch lived for over two hours, but that none sur- 
vived for three. This suggested that perch might be able to enter the lower waters 
of the lake with impunity to take advantage of the abundant food supply there, coming 
up above the thermocline at intervals to breathe. 
This possibility made it necesary to observe the behavior of perch in water from 
below the thermocline. On September 4 water was pumped up from 13.5 m. (oxygen, 
0.06 c. c. per liter; carbon dioxide, 5 c. ¢c.) into a large aquarium on the deck of a boat. 
Samples taken from the water in the aquarium showed that it contained about 0.3 c. c. 
of oxygen and 5 c. c. of carbon dioxide per liter. Nine fish, caught in a gill net half 
an hour before at a depth of 11.6 m., were placed in the aquarium and their behavior 
observed for two hours. They were compared at intervals with perch caught at the 
same time and place, which were kept in a large cage at the surface of the lake. One 
of the fish in the stagnant water turned on its side and became immobile (except for 
respiratory movements) after four minutes. After half an hour several were lying on 
their sides, but after an hour and forty minutes one individual was still right side up 
and, though inactive, appeared to be in normal condition. 
On the following day two perch, caught an hour before at 11.7 m., were again 
placed in water pumped from 13.5 m. into a glass aquarium, and their behavior was 
observed for an hour. Both of these individuals turned belly up within a few seconds; 
one floated at the top of the cage, but the other at times was at the bottom and at 
times at the top. At intervals both righted themselves, moved the fins, and wiggled 
about actively. After being in the stagnant water for an hour both were taken out 
and placed in the lake just below the surface. Half an hour later both had recovered, 
were right side up, and apparently in good condition. Two hours later both were 
released and swam away. During the time the perch were in the stagnant water the 
rapidity of their respiratory movements was observed, and the results, showing the 
number of respiratory movements per minute, are given as follows: 
Time. No. 1. | No. 2. Time. No. 1. | No. 2. 
32 28 
25 28 
21 33 
20 3r 
One individual stopped making respiratory movements for over two minutes in 
the midst of the experiment. In general, the rate of respiration decreased, but when 
the fish were placed in the lake again the rate rapidly increased. The rate of those 
