66 
Fishery Bulletin 1 14(1) 
(l/(l+(Stg$ Time /T50_2) A s2)) #additional stages would be added by 
# summing additional logistic equations here. A 
#fourth stage would require 2 more parameters: 
#T50_3 and s_3 
var=(l/( l+(Stg$ Time /T50_l) A sl))*(l-(l/(l+(Stg$ Time /T50_l) A sl)))+ #calculates 
(l/(l+(Stg$ Time /T50_2) A s2))*(l-( l/< l+(Stg$ Time /T50_2) A s2))) #the variance 
# additional stages require the variance for each 
transition to be added here. 
-sum(dnorm(Stg$Stage,ave,var A .5,log=TRUE)) #calculates the negative log likelihood 
) 
param=list(T50_l=10, T50_2=25,sl=-10,s2=-20) ttinitial parameter estimates. If the model is 
#expanded to more stages, then the 
^necessary parameters and estimates need 
#to be added to this list. 
mStage=mle( Stage, start=param) #fits the data to the model through the 
#use of maximum likelihood 
summary(mStage) #gives a summary of the fit, including estimates of the 
# parameter ; their standard errors, and the -2 log 
# likelihood of the fit. 
