Ae. Punt et al., ESTIMATING THE SIZE-TRANSITION MATRIX FOR TASMANIAN ROCK LOBSTER, JASUS-EDWARDSII, Marine and freshwater research, 48(8), 1997, pp. 981-992
Assessment of the southern rock lobster (Jasus edwardsii) resource in
Tasmania is based on a size-structured population dynamics model. One
of the most important inputs to this model is the set of matrices that
represent the season-specific probabilities of a lobster growing from
one size-class to another. These matrices are estimated from tag-reca
pture data within a maximum-likelihood estimation framework. Measures
of precision are determined from the asymptotic variance-covariance ma
trix. Various alternative models are contrasted for one site in the so
uth-east of Tasmania, and a best model is selected by the likelihood r
atio test. The growth model used is based on a generalization of the v
on Bertalanffy growth equation. Growth rates differ markedly among reg
ions around Tasmania, being slowest in the south and fastest in the no
rth. Growth of legal-size males is noticeably faster than that of lega
l-size females. it is shown that ignoring the effects of selectivity c
an lead to biased estimates of growth rate. An extension to the method
is presented and applied that estimates size-specific selectivity in
an attempt to eliminate this bias.