THE PYGMY WHITEFISH, PROSOPIUM COVLTERU IN 



WESTERN MONTANA 



G. F. Weisel,' D. a. Hanzel,2 and R. L. Newell^ 



ABSTRACT 



The pygmy whitefish, Prosopiuin coiilwri. is a glacial relict which has been considered 

 to be the most primitive of coregonines. It is relatively abundant in lakes of western 

 Montana and is undoubtedly an important source of food for Dolly Varden and lake 

 trout. Compared to other members of its subfamily, it is characterized by low meristic 

 counts. These counts differ somewhat in populations from Montana, Alaska, and Lake 

 Superior. 



Major food items consumed by the pygmy whitefish shift with availability but the 

 main reliance is on cladocera and chironomid larvae and pupae. The annual growth 

 in Flathead Lake, Mont., is greater than that in Lake Superior but below that in some 

 Alaskan lakes. No males were found older than age III and no females beyond age IV. 

 Many of the males mature at age I, a year earlier than most females. The spawning 

 season is in December and January when the fish move into tributary streams. The species 

 spawns in successive years. The fecundity of the Montana fish is similar to that of pygmy 

 whitefish from other areas. 



The pygmy whitefish successfully competes with other coregonines in reproduction by 

 spawning at a later date and earlier age, and by having smaller eggs which yield more 

 eggs per unit weight of fish. The small size and early age at maturity are considered 

 adaptations developed for survival in cold and nutrient-poor water during glaciation. 



The pygmy whitefish, Prosopium coulteri, is 

 considered a glacial relict that survived in 

 deep lakes after the retreat of the Wisconsin 

 glaciation. Until the past 20 years the species 

 was infrequently captured, or recognized when 

 it was. It usually inhabits depths of over 30 ft 

 and, because of its small size, escapes capture 

 by most fishing gear. The present distribution 

 is given as the Columbia, Fraser, Skeena, 

 Yukon, and MacKenzie River systems, and 

 both the Pacific Ocean and Bering Sea drain- 

 ages of southwest Alaska (Heard and Hartman, 

 1966). In 1955 the report of this little fish 

 from Lake Superior disclosed a remarkable 

 case of disjunct distribution (Eschmeyer and 

 Bailey, 1955). 



Only in recent years has it been recognized 



' Zoology Department, University of Montana, Mis- 

 soula, MT 59801. 



^ Montana Fish and Game Department, Kalispell, MT 

 59901. 



•* Department of Biology, Idaho State University, 

 Pocatello, ID 83201. 



how ubiquitous the pygmy whitefish is in 

 western Montana. It was first reported in 

 Montana by Schultz in 1941 from tributaries 

 of Lake McDonald in Glacier National Park. 

 The next report was from Bull Lake, a tribu- 

 tary to the Kootenai River (Weisel and Dillon, 

 1954). In the past 10 years it has been taken 

 with small-mesh gill nets from Flathead, Ash- 

 ley, Swan, Seeley, and the Little Bitteroot 

 Lakes — all tributary to the Clark Fork River 

 (Brown, 1971). Careful collecting will un- 

 doubtedly show the species to be present in 

 many other glacially formed lakes in western 

 Montana. 



Our studies show the pygmy whitefish to be 

 one of the most abundant fishes in Flathead 

 Lake. According to Hanzel's 1968-71 extensive 

 nettings, this species constituted 4.8% of the 

 total catch; it ranked in order only below lake 

 whitefish {Coregonus cli(peafo)-»iis), peamouth 

 {Mijlocheilus caunnns), kokanee {0)icorhy)ichus 

 iierka), northern squawfish {Ptychocheilns ore- 

 go)ieiisifi), Dolly Varden (Salveli)ius malma), 

 and yellow perch {Pcrca fl,avesce>if<). 



Manuscript accepted October 1972. 



FISHERY BULLETIN: VOL. 7L NO. 2. 1973. 



587 



