Length-Frequency Analysis

Length-frequency analysis estimates growth and mortality from the size distribution of catch samples, the standard tool where aged data are absent. It tracks modal progression: peaks in a length-frequency histogram represent cohorts whose modes shift rightward over successive samples, tracing the von Bertalanffy growth function and yielding asymptotic length L_infinity and the growth coefficient K. ELEFAN, developed by Pauly and David in 1981 and now run in FiSAT and the R package TropFishR, automates the fit, after which a length-converted catch curve estimates total mortality Z. It is the backbone of data-poor and tropical multispecies stock assessment.