180 
BULLETIN OP THE BUREAU OF FISHERIES 
Adult period, 75 millimeters. — Suckers of this period (3 to 15 inches in length) are 
shy fish, lurking among the stones on the bottom of the deeper holes along the creek, 
and probably in the deeper shoal waters of the lakes. While perch, bass, minnows, 
etc., frequently are seen leisurely feeding or resting in moderately shallow water, 
the white sucker is not seen unless the pool be approached cautiously, and only dur- 
ing the spawning season are large suckers found in shallow water in the daytime. 
They exhibit a shyness characteristic of trout, making off with great haste when 
disturbed. It is next to impossible to take them in a seine if the bottom is rough, 
for they escape through any gap, finding such places with great rapidity. Reighard 
(1915) reports seeing suckers feeding in the early morning. Suckers are taken on 
hook and line baited with earthworms, but mostly on cloudy days or when the water 
is turbid. Specimens removed from the traps in the morning regularly showed a 
well-filled intestine. From this and the extreme shyness of the fish it seems probable 
that its feeding is done in the darker hours. 
While gregarious in the adult stage, one finds individuals of all sizes between 
2 or 3 to 10 or 12 inches inhabiting the same pool or lagoon. In the lakes and larger 
streams, those of larger size — 8 to 15 inches in length — appear to feed and travel 
in bands of a score or more. These larger ones have been seen resting quite motion- 
less some 4 to 6 feet below the surface of the lake, and they refuse all bait. 
The food of the adult is not mixed with sand to any extent. Only 0.9 per cent 
of the food of 52 specimens was sand, as against 21 per cent in the case of fingerlings. 
At the beginning of this stage (3 inches) the sucker begins to hold the food particles 
in its mouth and to spit out the sand. This ejecting of the sand has been reported 
by Reighard (1915). The diatoms doubtless are ejected in this cleaning process, as 
they constituted but 3.6 per cent of the intestinal contents in 52 cases. The hold- 
ing of the food is possible because it now consists largely of insect larvae and nymphs. 
These facts are summarized in the following percentages, based on a study of 52 
specimens : 
Percentage 
Chironomidffi 30 
Diatoms and desmids 3. 6 
Rotifera - 0 
Arthropod fragments 5. 4 
Entomostraca 5 
Protozoa • 1 
Algae 2. 4 
Sand . 9 
Mollusk shells . 2 
Larger insect larvse and nymphs 4 : 31 
Debris (principally mucus) 22 
While the most distinguishing items of diet are the immature aquatic insects of 
large size (31 per cent), the total of these, together with the omnipresent midge 
larvae and fragments of insects, brings the total quantity of insects eaten by the 
adult fishes to 66.4 per cent. The adult sucker in this region must then be classed 
as an insectivorous species. Of the organic food but 6 per cent consists of plants, 
hence the fish is distinctly carnivorous in this as in the earlier stages. 
Most of the insect larvae and nymphs occur whole in the digestive tract, even 
larger ones, such as dragon-fly nymphs, being swallowed without fragmentation. 
4 Odonata, 9 per cent; mayflies, 9 per cent; and caddis flies, 13 per cent. 
