THREESPINE STICKLEBACK OF KODIAK ISLAND 



553 



Figure 13. — Dissection of female stickleback with eyed eggs in ovary. 



[of 1049] as August 3. Morton 3 found stickle- 

 back eggs in the stomachs of charrs taken in Kar- 

 luk Lake in June, July, and August, but not in 

 those taken in April, May, and September. 



A collection of sticklebacks, made along the 

 shore of Karluk Lake on July 15, 1956, had a 

 few spawned-out females, but most of the females 

 were ripe with eggs. Observations on July 25 

 showed many females still to be carrying eggs. 

 But a collection made on August 6 had no fish 

 with ripe eggs, all the large females having 

 spawned. 



In Bare Lake we have taken ripe females as 

 early as May 23 [1954] and as late as July 29 

 [1952]. Specimens less than 20 mm. standard 

 length were captured on June 7, 1954. Judging 

 from the size of the young-of-the-year in June 

 and July (fig. 6), many of the sticklebacks in 

 Bare Lake presumably spawn in May. 



A collection from Bare Lake on July 23, 1956, 

 had a few fish still gravid with eggs, but most of 

 the mature fish were spent. On August 1 all the 

 larger fish in a collection were spawned out. A 

 nest with eyed eggs in it was found on August 4, 

 and on August 15 a young stickleback was taken. 



These scanty data indicate that perhaps the 

 stickleback spawns earlier in Bare Lake than in 

 Karluk Lake. Such should not be the case if 

 light (length of day) were the sole factor con- 



3 Food studies of the Dolly Varden {Salvelinue malma) and 

 arctic charr (Salvelinus alpinus) at Karluk, Alaska, from 1939 

 through 1941. By William Markham Morton. (In preparation.) 



trolling spawning date. Bare Lake, being small 

 and shallow, warms faster in the early summer 

 and maintains a higher surface water tempera- 

 ture through the summer than does Karluk Lake 

 (fig. 4). It is suggested that water temperature 

 may influence the time of spawning. 



Spawning takes place in Bare Lake in shoal 

 water around the shores of the lake. In Karluk 

 Lake, too, many sticklebacks utilize the lake shore 

 for spawning. Congregations of possibly hun- 

 dreds of thousands of sticklebacks have been 

 noted by C. E. Walker at the lower ends of 

 Lower Thumb and O'Malley Rivers, the two 

 principal tributaries of Karluk Lake, from early 

 May until June 1950. "Walker states (private 

 communication) that the fish ascended these 

 streams to Thumb and O'Malley Lakes, where 

 they spawned. 



The literature contains many references to the 

 nest-building habits of the stickleback. In some 

 waters the male constructs an elaborate nest of 

 small sticks, twigs, or pieces of vegetation held 

 together by a sticky substance presumably se- 

 creted by the kidney (Wunder 1930; and others). 

 However, Vrat (1949) reports that the stickle- 

 backs which he studied in California did not use 

 leaves or twigs in their nests. These nests took 

 the form of a hole in the sand, excavated by the 

 male and shaped by strokes of his head. 



The nests in Karluk and Bare Lakes are well 

 hidden and camouflaged. The very few that we 

 have been able to discover did not contain sticks 

 or plant material but appeared to be made mostly 



