On length-weight relationships. Part II: Computing mean weights from length statistics

Abstract

Assuming a known length-weight relationship, the formula for calculating the mean weight from grouped length statistics is recapitulated. Then a simple analytical method for calculating mean weight from basic length statistics is developed which applies when lengths are approximately log-normally distributed or when normally distributed with a coefficient of variation (sd/mean) less than ca. 1/3. The method can be applied to other length distributions as well provided that the coefficient of variation is small.