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against seeding biomass. There is a suggestion, however, that at very high 

 seeding densities (e.g. as in 1927) mortahty might increase. When production 

 and surviving biomass are plotted against seeding biomass (weight of fry at 

 the start of the year) (Fig. 2) it is clear that both do not increase propor- 



1 2 3-4567 



Initial biomass of fry (metric tons) 



Fig. 2.— Yearling stock biomass and production plotted against seeding biomass of fry for sockeye 

 salmon in Cultus Lake (data from Picker & Foerster, 1948). The crosses are for the three 

 years after predator control. 



tionately but curve away towards a maximum at high seeding densities. 

 Plotting these data on double logarithmic scales (Fig. 3) shows that over the 

 range of densities that occurred the production is roughly proportional to 

 the o-8th power of the seeding biomass. It is doubtful if much significance 

 can be attached to this actual relationship, but it is interesting that the 

 production for the three years after predator control falls on a parallel line 

 showing a very similar relationship at about twice the production for a 

 given seeding biomass. Ricker & Foerster explain the higher yield of fry (or 

 biomass surviving at the end of the year) after predator control on the basis 

 of a much lower loss from predation and thus decrease in mortality rate. It 

 is clear, however, from plots of production and yield against seeding biomass 

 and seasonal plots of production in 193 1 and 1935 that the production itself 

 increased relative to seeding after predator control. This, however, can be 

 explained entirely by the survival of a much greater share of the early 



