Figure 7. --Mean daily water temperature during the 1959 and 1960 experiments. 



means for the corresponding 6- week recovery 

 periods are 58.5, 56,1, and 53.4 in that order. 

 These limited data suggest, then, that marking 

 success, although independent of mean 

 temperature during starvation, is related to 

 mean temperature during recovery. 



When we consider another time dependent 

 factor, size of the fish at the onset of starva- 

 tion, we find that the smaller the fish at the 

 onset of starvation the greater the marking 

 success. No relationship is evident between 

 the size of the fish at this stage and the per- 

 centage weight loss during starvation (9, 24, 

 and 9 percent in that order) or between mark- 

 ing success and percentage weight loss. 



The 1960 data reveals that the marking 

 success of the three 2-week test lots is re- 

 lated to relative growth of the control fish 

 during the corresponding period (60-, 48-, 

 and 26-percent weight gains by the control 

 fish during the first, second, and third starva- 

 tion periods in that order). Marking success 

 is also related to the percentage weight 

 gained by the three test lots during their 

 6-week respective recovery period (184, 158, 

 and 36 percent for the three lots respectively). 



Summarizing the discussion on the question 

 of why certain 2-week lots marked better 



than others, it appears that marking success 

 is strongly influenced by one or more time 

 (seasonally) related factors such as falling 

 temperature or reduced hours of daylight, 

 hence reduced growth during the recovery 

 period. To obtain optimum results starvation 

 should take place early when the fish are 

 small and their growth rate fast thus allow- 

 ing the major portion of their recovery period 

 to fall in midsummer when growth is still 

 relatively rapid. 



CONCLUSIONS 



The experiments described in this paper 

 were the first in a series to determine 

 whether a starvation-marking technique could 

 be developed to mass-mark populations of 

 hatchery-reared salmon. The results of these 

 initial tests have yielded certain conclusions 

 on one hand and point out the need for further 

 experimentation on the other. The conclusions 

 are: 



1. Under the proper conditions of timing 

 and duration, a highly recognizable mark can 

 be imprinted on the scales of hatchery-reared 

 sockeye salmon. This can be accomplished 

 with little mortality due directly to starvation. 



10 



