WHITE SUCKER 
175 
one-third-inch mesh, but only where the bottom was smooth. A seine 100 feet 
long and of 1-inch mesh was used in Cayuga Lake and the lagoons of Fall Creek, 
where specimens 10 to 15 inches in length were taken. About 40 specimens were 
taken by hook and line, the bait always being earthworms. 
For food analysis the material from the smaller specimens was fixed in the field, 
while from the larger ones it was prepared immediately upon arriving at the labora- 
tory. Either 4 per cent formalin or 70 per cent alcohol was used as a preservative. 
For sectioning, either Gilson’s, Bouin’s, or Perenyi’s fixation fluid was employed 
with equally good results. 
The region about Ithaca affords unusual opportunities to observe aquatic 
organisms under varied conditions, combining, as it does, cold, spring-fed brooks, 
gravel and bowlder-bottomed streams, areas of clay, cataracts with deep pools, 
sluggish waterways through cat-tail marshes, and the lake with shallow or deep 
waters near the shore. 
The material examined was taken between June, 1922, and August, 1923. 
Some collections were made every week except during December and January, 
when the ice made collecting very difficult. All the larger streams of Tompkins 
County were covered in collecting the fry and fingerlings, while the traps were set 
and seines drawn at points nearer the Cornell Campus — Cascadilla Creek, Fall 
Creek, and the lagoons of the latter and Cayuga Lake. 
PERIODS INTO WHICH FEEDING HABITS MAY BE DIVIDED 
The life history of the white sucker shows five periods that can be distinguished on 
the basis of its feeding activities. This is peculiar to the sucker to the extent that 
its feeding is correlated with the change in its mouth from the terminal to the inferior 
position. Some fishes show three or four periods, due to increase in their size and 
the correlated need for more nourishing diet. For the sucker the following periods 
may be distinguished, both by the general behavior of the fish and by the actual 
analysis of the contents of the alimentary tract. 
First or yolk-food period . — In a sense this period begins with segmentation and 
ends when the yolk has been entirely consumed. The fry is approximately 8 milli- 
meters long at hatching, and the yolk is found to be its food up to a length of 12 
millimeters. This may be called the “yolk-sac stage,” though the sac actually is 
reduced, so as not to appear in surface views, before feeding through the mouth 
begins. 
Top-feeding period . — From the time the fish begins to feed (12 millimeters), up 
to the change in the position of its mouth at 16 to 17 millimeters, it feeds upon organ- 
isms at or very near the surface of the water. This constitutes a very clearly-defined 
period in its life history, and the fry at this stage play a very different role in the 
economy of the stream life than do the older fingerlings and adults. 
Critical period . — This term is used to designate the actual period during which 
the feeding habit changes. It extends from the time when the fish begins to go to 
the bottom occasionally to pick up food to the time when it ceases to feed anywhere 
but on the bottom. It is a brief period, only a few days in duration, when the fish 
is 16 to 18 millimeters long. 
