FISHERY BULLETIN: VOL. 87. NO. 3, 1989 



Table 1 . — Simulated population of anchovy larvae based on a series of ichthyoplankton 

 surveys conducted in 1984. Tabulated values are the parameters (m and k) of negative 

 binomial distributions' fit to the population stratified by month, region, and temperature. 



'Negative binomial distribution where 

 (x-^ /(- 1 



P(X=x): 



m/m+ k)]'*[k/m+ /<)]* for x = 0,1,2,3,,,.. 



x'.ik- 1)! 

 ^Poisson distribution was used where P(X = x) = (m'e "j/x! for x = 0,1,2,3,. 



A two-step Gompertz growth curve (Fig. 6) was 

 used to determine the corresponding larval 

 length. The length at age was generated based 

 on a normal distribution with mean equal to the 

 length computed from the Gompertz growth 

 curve and a standard deviation equal to 0.2 times 

 the length. (The standard deviation is normally 

 proportional to the mean length at age.) The 

 coefficient of variation of 0.2 was arbitrarily 



chosen because no direct estimate of the stan- 

 dard deviation was available. These simulated 

 larvae, with assigned ages and lengths, com- 

 posed the catches. 



Sampling Biases 



The simulated catches were reduced to ac- 

 count for the effects of extrusion and avoidance. 



404 



