350 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
TIME OF FEEDING OF THE OYSTEK. 
The question of the time of feeding of the oyster will be an interesting one in the 
management of culture ponds. Here the ingress of water can be definitely regulated 
by tides day or night, to suit the feeding habits of the oyster. That the rising tide is 
the dining time of the oyster has usually been conceded; how far feeding activity is 
governed by daylight or darkness is, however, a question of interest. The results of 
the following examinations are noteworthy. 
In a favorable locality* three gatherings of twenty oysters each were made, all 
from the same station, at 7 : 20 a. m., 1 and 5 : 30 p. m. Care was taken to select oysters 
in every way similar in size and character, freedom from oyster-crabs, bryozoans, or 
sponges. The stomach contents were taken within half an hour after the time of col- 
lection. The total quantity of food in process of digestion at these times of day could 
then be crudely compared. To determine comparatively the richness or quality of 
food contents of each set of specimens, a simple color test was devised. The total 
food-bulks were placed in separate Hessler glasses (15 cubic centimeters, slender), 
and to the two darker fluids distilled water was carefully added until the three speci- 
mens, viewed from above, were of the same color. The volumes in each tube, now of 
about the same nutritive value, were readily measured and compared. The following 
are the results : t 
Time of 
day. 
Color. 
Amount in 
cubic cen- 
timeters of 
contents 
of 20 
stomachs. 
Food contents 
of 20 stomachs 
rendered of the 
same nutritive 
value and their 
bulks com- 
pared (cubic 
centimeters). 
Time. 
l 
Tide. 
Depth. 
Water 
temper- 
ature. 
Water, 
sp. gr. 
Remarks. 
Morning.. 
Pale watery . . 
.5 ■ 
7.20 
£ flood . . 
Feet. 
20 
60 
1. 0225 
W eat.her, foggy ; 
Noon 
Rich greenish- 
2.5 
12.5 
1. 00 
1 el)b ...j 
12 
60 
1. 0239 
bottom, packed 
shells. 
Wea ther, bright ; 
Night 
hrovrn. 
Light ocherous 
1 5 
5 0 
5.30 
Low.... 
g 
60 
1. 0225 
bottom, sponges, 
bryozoans. 
Weather, clear; 
bottom, red sea- 
weeds. 
It is noteworthy that during the night the oysters had been practically foodless; 
that, although the tide had well risen in the morning as late as 7 :20, the oysters had 
fed but little; that the bulk of ingested food was taken during the strongest daylight, 
morning and afternoon. This suggestion, as to the feeding habits of the oyster, is not a 
surprising one when we remember that it is during the strongest sunlight that diatoms, 
as plants keenly sensitive to the sun, are most active and are known to migrate in 
floating clouds from bottom to surface. 
* Myrtle Bush Creek, near Port Koyal, February 10, 1891 ; a fine bed of “ dropped-off ” raccoons, 
t The accompanying conditions of water are given in the table of analyses, p. 359, Nos. 108-110. 
