THREESPINE STICKLEBACK OF KODIAK ISLAND 



557 



sculpin Cottus aleuticus may eat stickleback eggs 

 and small sticklebacks. 



Sticklebacks are eaten by several kinds of birds 

 including probably mergansers (Munro and 

 Clemens, 1937), gulls, loons, and kingfishers. 

 The quantitative relationships are not known. 

 Of some significance to the overall ecology of the 

 lake may be the fact that the stickleback carries 

 one or more species of internal parasites which 

 are transmitted to other fish or to birds. 



The stickleback has been used to some extent 

 in northwestern Europe in the production of 

 fish oil and meal, and in Russia and possibly in 

 northwestern Alaska for human food. It has 

 been reported that sticklebacks on Kodiak Island 

 sometimes are used for dog food, and are con- 

 sumed by humans on occasion. For these uses 

 the fish are stored in frozen blocks. 



Relation to Red Salmon 



Aside from such intangible things as dual oc- 

 cupation of and competition for space, the rela- 

 tion between the stickleback and the production 

 of young red salmon involves four possible major 

 factors: the predation of the stickleback on the 

 salmon, food competition between the stickleback 

 and the young salmon, the use of stickleback fry 

 or eggs as food for the salmon, and the role of 

 the stickleback in the diet of chair and other 

 predators on the salmon. 



Predatory habits of the stickleback have been 

 mentioned by various authors. Kincaid (1919) 

 makes the (unsupported) statement: "The dam- 

 age done by the stickleback is out of proportion 

 to his size, as he is able to kill the fry of larger 

 fish, notably the salmon, for which reason the 

 stickleback is known locally as the Salmon 

 Killer." We have no evidence of sticklebacks in 

 Karluk and Bare Lakes feeding on red salmon 

 eggs or fry. We have not examined any stickle- 

 back stomachs taken in the spring while the 

 salmon fry were very small. Rounsefell (1958), 

 states that : "there seems to be little evidence 

 that they [sticklebacks] are actual predators (on 

 young salmon).'' Rounsefell cites "White (1930) 

 who performed experiments on the consumption 

 of brook trout (Salvelinus fontiiwlis) fry by 

 large trout of the same species and by adult 

 threespine sticklebacks. The results of White's 

 experiments showed the stickleback to be an al- 



most negligible factor in the loss of trout fry. 

 Rounsefell comments, "Salmon fry are much 

 larger than the fry of the brook trout, so that 

 there would seem to be even less chance of any 

 destruction." 



The feeding habits of the young red salmon 

 in Karluk Lake are not fully known. It is prob- 

 able that the fry eat insects and plankton ani- 

 mals, but the larger juveniles may eat a few 

 small fish. Therefore, although there may be 

 some points of difference, the food habits of the 

 small red salmon and the sticklebacks are simi- 

 lar in large measure. Both fishes eat insect larvae 

 (mainly chironomids) and plankton crustaceans. 

 The diet is suited to the fare. Whether and to 

 what extent the consumption of part of the avail- 

 able food supply by the stickleback has an ad- 

 verse effect on red salmon production is not a 

 matter easy to assess. 



As we have suggested above, small sticklebacks 

 may be an item in the food supply of the salmon 

 fingerlings, especially the larger smolts. How- 

 ever, data for making a quantitative estimate of 

 the effect on salmon production are lacking. 



Certain predators, in particular the arctic charr, 

 have been shown to utilize sticklebacks for food. 

 This use of sticklebacks may in some measure 

 relieve predation on the young red salmon and 

 possibly be a favorable factor in the production 

 of salmon smolts. However, relationships be- 

 tween predators and prey are complex and not 

 understood fully. A reduction in numbers of 

 sticklebacks present in Karluk Lake might mean 

 that more salmon would be eaten by the charrs. 

 Or it might mean only that the charr population 

 would decline, because the total food supply had 

 decreased, and thus the number of salmon smolts 

 eaten by chars might remain substantially the 

 same. 



SUMMARY 



The threespine stickleback. Gasterosteus acu- 

 leatvs. is found in large numbers in Karluk Lake 

 and Bare Lake in southwestern Kodiak Island, 

 Alaska. Its presence may have a relation to the 

 production of red salmon (Oncorkynchus nerka) 

 in these waters. 



This species of stickleback has a wide distri- 

 bution in the subarctic and temperate zones of 

 the northern hemisphere. It has had a history 



