Effects of length-at-age data on growth and management benchmark F-0.1 estimates in the face of size-selective mortality
Authored by J Martinez-Garmendia
Date Published: 1997
DOI: 10.1016/s0165-7836(97)00057-x
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Abstract
The effects of fishery-dependent and fishery-independent length-at-age
sampling in the face of size-selective exploitation on growth parameter
and management benchmark F-0.1 estimation are explored. An
individual-based population numerical model was used to simulate growth, natural and fishing mortalities and two sampling schemes for a
short-lived and a long-lived population under various exploitation
conditions. For the proposed sampling schemes, biases introduced in von
Bertalanffy growth parameters and F-0.1 estimates indicated that
fishery-dependent sampling was a much poorer source of length-at-age
data than fishery-independent data from populations affected by
size-selective mortality. Based on the assumed gear selectivity
patterns, catches of simulated trawls obtained under high levels of
exploitation provided poorer length-at-age data than when the catches
were obtained under low levels of exploitation. The opposite happened
for the length-at-age data from catches of fisheries operating with the
simulated gillnet selectivities. Also, selection of larger individuals
from the population by the gears affected both fishery-dependent and
independent length-at-age samples more than when small mesh-sizes were
used. For most of the cases studied, biases of F-0.1 showed similar
trends to biases of the parameter K, but with smaller absolute
magnitudes. It should be noted that these results are constrained by the
assumptions of the scenarios investigated and, therefore, they could not
be generalized. However, the approach proposed here offers interesting
possibilities for further exploration. (C) 1997 Elsevier Science B.V.
Tags
Dynamics
Variability
Parameters