Ds. Vaughan et Ml. Burton, ESTIMATION OF VON BERTALANFFY GROWTH-PARAMETERS IN THE PRESENCE OF SIZE-SELECTIVE MORTALITY - A SIMULATED EXAMPLE WITH RED GROUPER, Transactions of the American Fisheries Society, 123(1), 1994, pp. 1-8
Fish lengths back-calculated to all scale or otolith annuli are often
used for estimating parameters of the von Bertalanffy growth equation
in an attempt to increase sample size and presumably improve the fitte
d model. Lengths at early ages back-calculated from younger age-groups
sometimes are greater than lengths at the same age estimated from old
er age-groups, referred to as Lee's phenomenon. Lee's phenomenon can b
e simulated with use of size-selective mortality and moving averages t
o incorporate error dependency in lengths at age. To evaluate the appr
opriateness of using back-calculated lengths at formation of all annul
i in growth analyses when size-selective mortality is present, we used
simulated data based on von Bertalanffy growth parameters and total m
ortality for red grouper Epinephelus morio from the southeastern U.S.
Atlantic coast. Asymptotic length (L infinity) and the growth coeffici
ent (K) showed greater bias when estimated with back-calculated length
s at all annuli than when estimated only with back-calculated lengths
at the most recent annuli whenever Lee's phenomenon (or its reverse) w
as present. One should use only lengths back-calculated to the most re
cent annuli when estimating growth parameters representative of a popu
lation.