4 



BULLETIN OF THE BUEEATJ OF FISHEEIES 



completely enumerated, free from admixture with the output of other rivers, and their 

 spawning escapements can be led through the gates of counting weirs and the num- 

 bers accurately ascertained. For this reason they have been selected for this experi- 

 ment. A counting weir was first installed in the Karluk River in 1921 and in the 

 Chignik River in 1922, and they have been maintained in each subsequent year. 

 The present report deals with the results thus far obtained in the Karluk River, 

 leaving for later consideration the parallel series of determinations in the Chignik 

 w Bj t g rsii 6 d 



KARLUK RIVER WATERSHED 



Karluk River and the lakes from which it takes its source are located in the 

 western part of Kodiak Island, approximately 154° west longitude and between 

 57° and 58° north latitude. The outlet of the river, which is approximately 30 

 miles long, is into Shelikof Strait, a short distance east of Karluk Head, one of the 

 most distinctive and conspicuous landmarks of the Alaska coast. 



The lakes are situated about 350 feet above sea level, as determined by an 

 aneroid barometer, and are three in number. The largest lake, Karluk Lake proper, 

 is 12 miles long by 2 miles in width at the widest place, and the area is approximately 

 14.6 square miles. It extends almost due north and south, with the outlet at the 

 northern end. There are two smaller lakes (Thumb Lake and O'Malley Lake J ) 

 above the main lake. The accompanying map (fig. 1) shows these lakes, the main 

 tributary streams, and the depth contours, as determined by a reconnaissance 

 survey made by sextant and plane table during the summer of 1926. The lake is 

 surrounded by mountains that rise abruptly to a height of about 2,500 feet above 

 the level of the lake, and most of the tributary streams drop down abruptly from 

 these mountains, tumbling over bowldery beds, which appear to be anything but 

 favorable spawning grounds. From a few hundred yards to a mile or so of the 

 lower courses of these streams is accessible to the spawning salmon, but their ascent 

 usually is stopped abruptly by insurmountable falls. 



Upper Thumb River (above Thumb Lake), Canyon Creek, and Falls Creek 

 are the largest streams of the system. They meander for some distance through 

 comparatively wide valleys and offer apparently by far the best spawning conditions. 

 The underlying rocks are almost entirely shales, with an occasional small ledge of 

 quartz. In the absence of any calcareous rocks, the water is extremely soft (a 

 sample analyzed through the kindness of Dr. E. A. Birge, of the University of Wis- 

 consin, indicated only about 4.5 cubic centimeters of fixed carbon dioxide per liter). 

 The basin is evidently of recent glacial origin, as is indicated by the numerous 

 cirques to be seen on the mountains, by the distinctly U-shaped contours of the 

 valleys, including the bottom of the lake, and by numerous fine examples of glacial 

 erosion to be seen on the exposed bedrock along the streams. Karluk Lake proper 

 evidently was made by the formation of a large terminal moraine at what is now 

 the foot of the lake. 



The "lake is of such recent origin that the shores have been very little modified 

 by the action of the streams that enter the lakes. In only a few places has the 

 shore line been built out by the deposit of silt and bowlders from the mountain sides, 



• Named in honor of the present Commissioner of Fisheries, who has done so much to further the study and scientific care 

 of the salmon fisheries of Alaska. 



