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BULLETIN OF THE BUREAU OF FISHERIES 
Fingerling 'period . — This period extends from the critical period (17 or 18 milli- 
meters body length) to approximately 75 millimeters in length. The fish during this 
stage comes nearest to being what is suggested by the term “mud feeder.” Lim- 
ited by its size to small particles of food, and by the position of its mouth to the 
bottom as a source of nourishment, it takes a varied diet of the bottom-inhabiting 
organisms. 
Adult period . — Fish longer than 75 millimeters may be considered adults as 
regards their feeding. They are no longer “mud feeders,” in the sense used above, 
for while a fish may take mud and sand into its mouth only organisms are swallowed, 
and these consist principally of insect nymphs or larvae. The almost complete 
elimination of microorganisms and the high percentage of macroorganisms, nymphs, 
mollusks, etc., distinguish this stage from all the others. 
DETAILED ACCOUNT OF FEEDING HABITS AND FOOD 
YoTk-jood period . — The newly hatched fish has a well-filled, cylindrical yolk sac 
extending from the heart to the anus. The mouth is not yet open, and all nourish- 
ment is obtained from the yolk. The fish lies on the bottom but makes erratic 
motions that elevate it a few inches from time to time. Within two or three days the 
yolk sac has been reduced so that the fish apparently has no yolk left. This is so at 
9 millimeters; at 11 millimeters the mouth is open; and at 12 millimeters the first 
food is taken. 
Top-feeding period . — While fry of 12 to about 25 millimeters were collected from 
62 points scattered along 10 streams in Tompkins County, it was thought wise to 
make daily observations of these early stages on fish confined in a pond, also. 
Accordingly, a pond 4 by 6 feet was dug where there was a slow seepage, both in and 
out, through the soil. The pond averaged 16 inches deep, with sides and bottom made 
of earth. Early in the spring it was fertilized by the addition of 1 quart of well- 
rotted manure and 1 pint of dried milk albumen. No organisms were intentionally 
introduced, yet the young suckers found a rich fauna and flora there in May. 
To observe the earliest feeding, young fry were put into this little pond on May 
22. They were but 2 and 3 days old, having been reared to this point in the Meehan 
hatching jar indoors. 
During the first day many of them lay on the bottom, though a few main- 
tained themselves near the surface by swimming. Soon all were swimming at the 
surface, and on May 27, when 9 days old (12 millimeters in length), the yolk was 
all gone and yet no food except a single diatom was present in the individuals ex- 
amined. When 14 millimeters long or 11 days old (on May 29), samples showed 
food in the digestive tract. This earliest food, taken in the nursery pond, showed no 
important difference from that taken in the various streams of the region, and con- 
sisted of Protozoa (Euglena), Entomostraca (Cyclops adults and nauplii), chironomid 
larvae, Rotifera, and diatoms. The following list gives the percentages of each 
organism entering into the food of fry between 12 and 16 millimeters in length, both 
in the nursery pond and in four of the principal streams of the county: 
In the nursery pond (9 specimens): Chironomid larvae, 15; Entomostraca, 37; 
diatoms, 1.3; Protozoa (Euglena), 27; Rotifera, 18. 
