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THOROLF LINDSTROM AND NILS-ARVID NILSSON 



relatively wide tolerance of habitat type, a flexibility of feeding habits and 

 in general share many resources of their environment with several other 

 species offish'. 



The method employed by the present authors is to study the ecology of 

 some whitefish species when living sympatrically in different combinations 

 and different lakes. Svardson (1954, I957, 1958) has shown that there are 

 some indications that a whitefish species restricts its niche when living 

 sympatrically with other wliitefish species and that this suggests an effect of 

 competition. Material from such lake studies cannot be expected to be as 

 conclusive as laboratory experiments, when it is considered that the effect of 

 competition cannot be well delimited from the effect of differences in the 

 genetic equipment of populations belonging to the same species, nor from 

 environmental differences between lakes other than the differences in the 

 whitefish fauna. 



Fig. 2.— Map. Lake Vojmsjon is deep, Lakes Uddjar and Storavan are shallow. Altitudes 413, 

 419 and 419 m. Stations A, D and G are the spawning streams of C. peled. 



The genetic differences between populations of one whitefish species are 

 illustrated by Fig. i, the number of gillrakers within populations being a 

 stable character according to Svardson (i957, IPSS). Interspecific differences 

 are also illustrated in Fig. i. Both kinds of differences illustrate Svardson s 



