| Body length variability bas been studied in fish schools and eohorts of two tropical pelagie species. The data, and simulations associated with them allow the variations in standard deviation of cohorts to be followed, and hypotheses on spawning duration or population structure ean thus be tested. As the fish grow, the variability increases more rapidly in young eohorts than in schools with the same mean length. For older fish, the inverse phenomenon is observed: while the standard deviation of individual lengths deereases in a cohort as it gets older, this parameter continued to inerease in sehools as the mean length increases. This shows that schools of young fish eannot be eonsidered as representative of the cohort length frequency distribution, whereas... |
