254 



SALMON OF THE KARLUK RIVER, ALASKA 



spawning grounds during the last of June and the peak of the spawning occurs during 

 the third week of July. These fish populate all the spawning streams entering the 

 lake and, to a slight extent, certain parts of the lake shores where seepage through the 

 gravel promotes conditions suitable for spawning. By the end of July or the first week 

 of August the fish have completed spawning, and there is a definite scarcity of live 

 fish on the spawning grounds. During late August, fish again appear in numbers on 

 10 



17 24 31 7 14 21 28 5 12 19 26 2 9 16 23 30 6 13 20 27 4 II 



MAY JUNE JULY AUG. SEPT. OCT. 



Fiocke 2.— Percentage of total run appearing each week during season. 



the spawning grounds. An appreciable percentage of the fall run spawns along the 

 beaches, and some of the fish spawn in the Karluk River for a distance of a mile or two 

 below the lake, an area never populated by fish of the spring run. The majority of the 

 fish in the fall run do spawn, however, in the tributary streams of the lake. 



Although the two runs of fish spawn, to a great extent, on the same spawning 

 grounds, the time interval precludes a thorough interbreeding of the two populations. 

 The only interbreeding possible is between the late spawners of the spring run and 

 the early spawners of the fall run. Whether or not the separation between the two 

 groups has been sufficient to produce any anatomical differences that might be detected 

 biometrically has not been determined conclusively. Even though the differences 

 could not be detected biometrically, such an absence of differences would not repudiate 

 the theory of two populations of red salmon inhabiting one watershed and spawning 

 in the same gravel. Environmental conditions undoubtedly do account, in a large 



