SIMPLE MODEL FOR ASSESSING POTENTIAL LOSS 

 1000.0 



53 



100.0 — 



10.0 — 



60 90 



t, days 



150 



Fig. 1 Values of U, the factor by which adult loss is underesti- 

 mated, for specific daily natural mortality rates (n), occurring over 

 varying periods of entrainment (t). 



planktonic eggs and larvae often exceed 5%/day. Particularly high 

 mortality rates are evident early in the planktonic life stage or when 

 the planktonic life stage is of short duration. 



Figure 1 shov^^s a series of curves computed by varying the 

 duration of exploitation of planktonic life stages by the power 

 station. These curves indicate the factor U, by which the equivalent- 

 adults model will underestimate potential adult loss at specific 

 natural mortality rates. In calculating this factor we assume constant 

 vulnerability to entrainment and immediate removal (through decay, 

 predation, or loss of buoyancy) of eggs or larvae that die naturally: 



U 



,Mt/2 



(3) 



where M is the instantaneous natural mortality rate and t is the 

 duration of entrainment in days. 



In Eq. 3, U represents a factor that, when multiplied by the 

 number of eggs or larvae entrained, is equivalent to the number of 

 eggs or larvae originally produced and which would have been 



