APPLYING SURVIVAL CURVES 45 



CALCULATING DAILY POTEIMTIAL ADULT LOSSES 



Potential adult loss can be calculated on a daily basis (N^i) 

 through the entrainment period. Numbers of larvae entrained each 

 day are multiplied by increasing survival rates calculated from the 

 ratio of adults to larvae occurring each day: 



NAi = NLiSLAi-NLi^ (8) 



where Nli = number of larvae entrained each day 

 ^LAi ~ survival rate from larva to adult 

 A = number of adults 

 Li = larval population size 



However, since NLi/Li is a constant (0.5617o) representing the 

 percentage of occupied waters, and presumably larvae, entrained 

 each day, Nai = 0.00561 x A = 2614 and Na = Nai x 

 40 = 104,560. 



LARVAL REDUCTIOIM METHOD 



Actual reduction of a larval population caused by entrainment is 

 less than total numbers entrained because the total numbers include 

 larvae that would have died from natural causes by the end of the 

 pelagic period; e.g., the number of walleye larvae entrained in 

 40 days is 2.26 x 10^, and larval reduction is 673,500. Larval 

 reduction is csilculated by multiplying the estimated number of 

 40-day-old larvae (3.0 x 10^) by the percent reduction, 22.45% (as 

 described in Eq. 2). 



Multiplying larval reduction by survival rate from 40-day-old 

 larva to adult (0.1553) gives an Na value of 104,595. The survival 

 rate used is the ratio of adults and 40-day-old larvae (Table 1). 



The simplest approach for calculating Na is to assume that the 

 percent reduction of adults is equivalent to the percent reduction of 

 larvae (22.45%). This calculation yields a potential adult loss of 

 104,617. 



DISCUSSION 



Interpretations of the equivalent-adults model of Horst (1975) 

 have generally resulted in minimal projections of potential adult loss. 

 The primary causes are using high fecundity values, representing the 



