330 



THOROLF LINDSTROM AND NILS-ARVID NILSSON 



The fry and young of C. peled are for some time isolated from other 

 whitefish young and occupy the spawning stream and the lake downstream 

 near the inlet. This conclusion is based on observations of the distribution of 

 the spawning parents, since satisfactory identification of the young (by 

 counting the giUrakers) is not possible until late July. The habitat segregation 

 between C. peled and C. lavaretus is broken down during late summer and 



30- 



O 



Date 



23/7 



Year 1954 



Station E 



Species C.peled 



Fig. 3. — Food of young Coregonus peled and C. lavaretus in Lakes Uddjar and Storavan. Number 

 of stomachs with plankton (white cokimns) or insects (black columns) forming more than 

 half the stomach content. The intraspecific variation indicated by the figure is probably 

 in part attributable to a diurnal feeding cycle, the young feeding on plankton in the afternoon 

 and insects in the night. 



autumn as the C. peled young move out in the lakes downstream from the 

 spawning places. Also essential for understanding the first-year biology are 

 the striking similarities in the feeding habits of young C. peled and C. lavaretus 

 during late summer and autumn (Figs. 3 and 4), and the fact that the growth 

 curves of the two species do not diverge until after the first year, although 

 C. peled fry hatch earher and are longer at hatching (Fig. 5). 



These facts are interpreted as follows. There is an urge to grow at a certain 

 rate and to reach a minimum length at the end of the first year. Ricker & 



