Virtual Population Analysis and its approximation, Cohort Analysis are standard techniques for stock assessment when historical catch-at-age data are available. Jones proposed a length-cohort analysis in which length frequency data are used to construct a synthetic cohort when information about growth and mortality is available but age data are not. It is assumed that the length frequency distribution of a catch made up of many year classes at any time is representative of the catch from one cohort over the years in the fishery.