LO ET. AL.: ESTIMATES OF LARVAL MORTALITY 



Start an Iteration 



HI 



Sample allocat ion 

 II ->month -xeqloii: 

 n( 1 , } ) = pos . tows I n 

 month 1 and region j 

 (Table 2, appendix) 



Determine start i iig 

 survey time 



Start a month 

 and region 



7: Determine 

 time between tows 

 UB ing Gamma d 1st 

 (Table 3) 



Compute nu 

 zero tows 



Generate temp by norm 

 d 1st . and compute t ime 

 of tow for pos , tow 



Por eacli zero tow, 

 generate temperature 

 and compute t ime ot 



of tow 



Generate total 



Catch by NBD 

 (see 3 below) 



Assign age ( t ) to 

 each larva by 

 Pareto survival ship 

 function with para. 

 (1 N((l. 0.2 ID 



1MB ,p(lnput) 



Assign live 



length (L) to each larva 

 L = C[t) + N(0,f (t ) x0.2| 

 where £(t) Is Gompertz 

 growth curve 



IGR (Q^ .a ] (input) 



Shrinkage 



of live length 



Extrusion 

 and avoidance 

 by binomial 

 (50, P) 



Standard haul 



factor (SHF) 



N ( 4.96,0-S67 | 



Model catctl by tow. 

 obtain parameter 

 estimates oE UliD-.x ,k^ by 



region and temperature 



(Table 1) 



Figure 1. — Flow chart of the simulation. 



Allocation of Sampling Effort 



Simulated population encountered by plankton 

 tows was computed according to their distribu- 

 tion in 1984 by month and region (Table 1). The 

 portion of simulated tows that contained an- 

 chovy larvae was similarly determined (Table 2; 

 App.). In this way, the sample size (number of 

 tows) could be varied and yet still retain the 

 spatial and temporal distribution of sampling ef- 

 fort that was used in 1984. The time of the sim- 

 ulated tows was assigned by randomly selecting 

 a value from a Gamma distribution fitted to the 



actual time between tows in each region (Table 

 3; App.). 



Larval Mortality Rate 



Because it was found that anchovy larvae suf- 

 fer higher mortality during the first-feeding pe- 

 riod than during later stages, a Pareto function 

 describes the survival of anchovy larvae younger 

 than 20 days adequately (Hewitt and Brewer 

 1983; Lo 1985, 1986). In* the present study, we 

 used the Pareto function to assign age to the 

 larvae in the population (Table 1; Fig. 5; App.). 



401 



