In 1976–1988 young-of-the-year fish was caught biweekly
to monthly at 5 sites in the open water zone of
Lake Tjeukemeer using a 5 m beam trawl (cod end
5.5mmknot-to-knot) and measured to the nearest 0.5 cm
(fork length). Maximum length at the end of the year was
estimated by averaging the largest three observations
(each based on 50–100 specimens, if available) in the
period September–December of each year. Data on
timing of the onset of larval growth were obtained in
larval survey with hoopnets (Mooij, 1989, 1996).