REPRODUCTION AND RECRUITMENT IN FRESHWATER FISH 291 



production, leading to a bigger population on hand to grow during the 

 latter part of the growing season. Production was about doubled by predator 

 control, but yield increased between three and four times. 



Further data on the effect of seeding (or stocking or spawning) density on 

 juvenile production and 'yi^l^' of recruits is provided by preliminary data 



0-3 

 Init-ial 



0-5 

 biorr 



1-0 3 5 10 



iss of fry (metric tons) 



Fig. 3. — The data of Fig. 2 plotted on logarithmic scales. 



I have obtained for trout {Salmo trutta) in a beck in the EngUsh Lake District. 

 Observations on spawning and survival through the first year had indicated 

 survival rates from egg to yearling trout of about o-o6 (M =2-8) with an 

 indication that much of the mortahty occurred soon after the fry began to 

 feed. Accordingly in 1959 flood control was installed, and part of the beck 

 divided by fry-proof screens into a number of similar sections. A different 

 20 



