Note that the ages do not correspond directly with the ages of 50% maturity. The mean length at maturity for male and female porbeagle is roughly 200 cm and the split in the data is on this basis. The ages above correspond to these lengths. These equations were used in Gibson and Campana (2005), but were modified for the current model for CPUE by weight by adding weight at age to the right-hand sum and by increasing the number of q’s (one for each boat in each area and each season).
Following Harley (2002), the sex specific predicted length composition in the catch is a function of the population age composition, the selectivity curves and the distributions of length at age:
.
Here, the sex-specific length proportions at age () is given by:
where is the size of the length increment (5 cm in this analysis). Here we used the same growth analysis used in Campana et al. (2001) and Harley (2002), assuming a von Bertalanffy growth model to model the relationship between length and age, as well as a linear relationship between and la. Constants are provided in Table 8.
is a function of 
.
) is given by:
is the size of the length increment (5 cm in this analysis). Here we used the same growth analysis used in Campana et al. (2001) and Harley (2002), assuming a von Bertalanffy growth model to model the relationship 
and la. Constants are provided in Table 8.