174 
BULLETIN OF THE BUREAU OF FISHERIES 
The following illustrations will make clear the fact that suckers vary in their 
food according to place, age, and season. 
In respect to the influence of locality, which possibly is associated with varia- 
tions in the distribution of food organisms, we may cite such instances as the fol- 
lowing. Of two suckers of the same length and collected on the same date but 
from two different streams, one contained 100 per cent Entomostraca and the other 
but 5 per cent. The direct influence of the size of the fish is seen in a case where, 
at the same time and in the same creek, a 1-inch specimen was found to contain 
90 per cent chironomids while a 4-inch fish had taken 80 per cent caddis-fly larvae. 
The effect of season is illustrated by the fact that in summer one may find 
suckers that are full of algae, while in winter this item seems quite absent from their 
diet. Moreover, it has become increasingly apparent and equally puzzling that even 
small fry exhibit what we can assign at present only to individual taste. In the 
same small nursery pond (3 by 5 feet) the following diet was selected by fry that 
measured 17 to 19 millimeters in length. On June 9 one specimen contained 80 
per cent sand, another 80 per cent chironomids; on June 12 one specimen contained 
80 per cent Rotifera; and on June 16, one individual contained 80 per cent Difflugia, 
and another 70 per cent Entomostraca. It is obvious that limited observations here 
would lead to widely divergent conclusions. Even among 4-inch suckers taken the 
same day and in the same lagoon one showed 90 per cent Odonata nymphs while 
another showed 60 per cent chironomids and no Odonata. 
While the factors here considered evidently alter the feeding habits of this 
species, there are probably others that likewise enter in. Of these may be suggested 
floods with their resulting debris, burying the bottom fauna; parasites that attack 
the sucker, filling its alimentary tract; and local differences in temperature of the 
stream or lake. Seasonal changes in the time of the appearance of its food organ- 
isms also would play a large part. 
The diverging conclusions hitherto reached regarding the food of the sucker 
can be understood, therefore, and it is obvious that an extended survey of its feeding 
habits alone would afford a basis for generalizations on this point. 
It is the aim of this paper to record the results of such a survey, which, while 
limited geographically in the wider sense, is probably more extensive in respect to 
numbers examined, age, and season than any previously recorded. 
FOOD 
It was necessary to use several methods in collecting the material utilized. 
For fry up to about 20 millimeters in length a dip net of very fine mesh, such as 
one made of cheesecloth, was necessary to prevent the escape of the tiny fish. From 
this size to fingerlings of 2 to 3 inches the fish were taken by means of a stout-handled 
dip net of coarser mesh — viz, eight meshes to the inch. 
For fishes over 3 inches in length other methods had to be used. The wire- 
cage trap proved the best of these. These were made of both fine and coarse mesh — ■ 
viz, one-third-inch square mesh and 1-inch round mesh. They had one or two funnel- 
shaped entrances, the passage narrowing down to about 4 inches in diameter. Such 
traps were baited with bread and placed in deep spots in the stream known to be 
frequented by suckers. A few were secured by a minnow seine 8 feet long and of 
