558 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



of much confusion in classification and nomen- 

 clature, largely because of wide variations in 

 morphological characters from one locality or one 

 type of environment to another. The stickleback 

 in Karluk and Bare Lakes is of the partially 

 naked (few lateral plates) form, which is char- 

 acteristic of populations that reside permanently 

 in fresh water. Counts of lateral plates and fin 

 rays show the populations of the two lakes to 

 be discrete. 



Estimates of numbers of fish in the stickleback 

 populations are difficult to make. Sticklebacks 

 appear to be more numerous in Karluk and Bare 

 Lakes than any other species. There is evidence 

 of considerable fluctuation in numbers from year 

 to year. 



The sticklebacks are often to be found in large 

 numbers along the shoals and have been observed 

 on the surface in the center of the lake and in 

 small numbers in deep water. Apparently there 

 is little or no movement to and from the ocean, 

 but spawning runs ascend the two main tribu- 

 taries of Karluk Lake to Thumb and O'Malley 

 Lakes. 



The species is at least moderately hardy and 

 resistant to adverse conditions. It carries several 

 species of parasites in these waters, notably the 

 pleroceroid of a cestode (Schistocephahis) which 

 has a plankton crustacean (Cladocera) as its 

 initial host and a bird as the final host. 



The sexually mature fish have both male and 

 female gonads. The male has paired ovaries and 

 the female a mass of testicular tissue. A large 

 female from Karluk Lake had several eyed eggs 

 in the ovary. 



Spawning takes place in early summer. In 

 some years a part of the spawning occurs as late 

 as August. In these waters the male does not 

 use plant material to any great extent in con- 

 structing the nest (as has often been reported in 

 the literature), but makes a nest of sand cemented 

 together with a secretion from within his body 

 and more or less buried in sand and gravel in 

 shoal water. Sticklebacks may spawn also in 

 weed beds, with little or no nest construction. 



The lifespan is about two and one-fourth years. 

 A standard length of 60 to 65 mm. is attained in 

 Bare Lake and up to 80 mm. in Karluk Lake. 

 Spawning may occur only once during life or 



at most twice. At least part of the fish die 

 within a few weeks after spawning. 



The principal foods for the stickleback in both 

 lakes are midge fly (Chironomid) larvae, and 

 plankton Crustacea (Copepods, Cladocera, Ostra- 

 coda). Minor items include other insects, water 

 mites, rotifers, small clams, snails, leeches, and 

 stickleback eggs. Stomachs examined at various 

 times during the summer did not contain eggs 

 or fry of fish other than sticklebacks. The period 

 covered by these examinations included the 

 spawning time of the red salmon, but not the 

 time of emergence of red salmon fry. 



The stickleback is a component of the food of 

 the arctic charr, which is a predator also on young 

 red salmon. Birds, rainbow trout, and possibly 

 large juvenile coho salmon eat sticklebacks. 

 Small sticklebacks may be used to a small extent 

 as food by the larger juvenile red salmon. 



The principal means by which the stickleback 

 in Karluk and Bare Lakes may influence red 

 salmon production include competition with 

 young salmon for food and by reducing predator 

 pressure on red salmon by furnishing food to the 

 charr. Quantitative information is insufficient to 

 assess accurately the benefit or harm to salmon 

 production caused by the stickleback population. 



LITERATURE CITED 



Baxter, Hae. 



1956. Effectiveness of gill nets and sport fish tackle 

 in sampling fish populations. Quart. Progress Re- 

 port, Federal Aid in Fish Restoration ; U. S. Fish 

 and Wildlife Service and Alaska Game Commis- 

 sion, June 30, 1956. 149 pp., mimeographed. 

 Bertin, Le6n. 



1925. Recherches bionomiques, biom^triques et sys- 

 tematiques sur les epinoches. Ann. Inst. Oc^anogr. 

 Monaco, vol. 2, pp. 1-208. 

 Bigelow, Henry B., and William C. Schroeder. 



1953. Fishes of the Gulf of Maine. U. S. Fish and 

 Wildlife Service, vol. 74, Fishery Bulletin 53, pp. 

 1-577. 

 Carl, G. Clifford. 



1953. Limnobiology of Cowiehan Lake, British Co- 

 lumbia. Jour. Fish. Res. Bd. Canada, vol. 9, pp. 

 417-449. 

 Cope, Oliver B., Claude M. Gjullin, and Alf Storm. 

 1949. Effects of some insecticides on trout and sal- 

 mon in Alaska, with reference to blackfly control. 

 Trans. Amer. Fish. Soc, vol. 77, pp. 160-177. 

 Cox, Philip. 



1922. Results of the Hudson Bay expedition, 1920. 

 II. The Gasterosteidae of Hudson Bay. Contrib. 

 to Can. Biol., 1921, No. 10, pp. 149-153. 



