ON THE COMPETITION BETWEEN WHITEFISH SPECIES 331 



Foerster (1948) have pointed out that a rapid growth can imply that the time 

 decreases during which the young are vulnerable to predation (c£ also Larkin 

 & Smith, 1954 and Foerster, 1954)- The interpretation is also consistent with 

 the observations that the first-year growth is fairly stable and does not react 

 in the same way as adult growth (Piile, 1941 and Le Cren, 1958). 



1000- 



100 



^jBosmina ^ HeLerocope 



^ Polyphemus | DipLera, pupae and imagines 



^ Holopedium Q Hemiptera 



IJ Cyclops R OLher insects 



^1 



^X 

 XX 



.in 



DaLe 23/7 1954 



station E 



19/7 1954 23/7 1954 24/7 1954 



C E B 



/ 

 / 

 /_ 



'^ 



/x 

 /x 

 /x 



/x 



100 



/ 



'A 



■: 

 ■ : 



12/8 1959 

 E 



Species C.peled C.lavaretus 



C. pe I ed 



16-17/8 1959 

 F 



C . lavaretus 



0-5 



Fig. 4.— Food of young Coregonus peled znd C. lavaretus in Lakes Uddjar and Storavan. Mean num- 

 ber of the different food items per stomach. The material indicates pelagic feeding habits. 

 In the left part of the diagram only plankton is represented though insects also existed in 

 the food — cf Fig. 3. In the samples from loth October 1954 (represented in Fig. 3) the 

 food consisted only of Bosmina. Note: the log. scales for plankton and insects differ. 



