410 
BULLETIN OF THE BUREAU OF FISHERIES 
the greatest width is 3.1 kilometers (2 miles). The area is 39.5 square kilometers 
(15.2 square miles) and the maximum depth is 126 meters (413 feet). The mean 
depth is 48.6 meters (159 feet). The surface of the lake is about 106 meters (350 
feet) above sea level, so that the deepest part of the basin is about 20 meters (65 feet) 
below sea level. 
The lake is surrounded by mountains which rise to a height of 760 meters (2,500 
feet) and the immediate shores consist of shale with an occasional small ledge or vein 
of quartz. The lake basin appears to be of recent glacial origin and the water is 
impounded by a large terminal moraine at the north end. In general, the beaches 
are composed of gravel and bowlders of various sizes. The shores are still in a 
youthful stage and the subaqueous terrace is poorly developed; as a result the bottom 
slopes away abruptly from the shores. The outlet, the Karluk River, flows out of 
the north end of the lake; it is a stream of considerable size and it is about 48 kilo- 
meters (30 miles) long (Gilbert and Rich, 1927). A rough estimate of the quantity 
of water discharged into Karluk Lake by the more important tributary streams was 
placed at 7 cubic meters per second in late August 1928. 
The narrow subaqueous terrace and the steep slope of the bottom make condi- 
tions unfavorable for the growth of the large aquatic plants along most of the shore; 
such growths are found in only three favorable localities. Filamentous algae are 
found in considerable abundance on submerged rocks and bowlders along the margin 
of the lake. The shores are well covered with groves of cottonwoods, alders, birches, 
willows, and shrubs. 
Thumb Lake is situated about the middle of the east side of Karluk Lake (fig. 1) ; 
it is about 1 kilometer (% mile) long and half a kilometer (% mile) wide. Its maxi- 
mum depth is 10 meters (33 feet). A short stream known as the Thumb River con- 
nects Thumb Lake with Karluk Lake. 
O ’Malley Lake is situated at the south en d of Karluk Lake ; it is about 3 kilometers 
(2 miles) long and % of a kilometer (% mile) wide. It has a maximum depth of 12 
meters (40 feet); and its outlet, the O’Malley River, flows into the south end of 
Karluk Lake. 
fc Gilbert and Rich (1927) published a hydrographic map of Karluk Lake which was 
based on surveys and soundings made in the summer of 1926. The data concerning 
the area and the volume of the lake, which are given in Table 1, are based upon 
measurements of the original map prepared by these authors. 
