Nl. Andrew et Y. Chen, OPTIMAL SAMPLING FOR ESTIMATING THE SIZE STRUCTURE AND MEAN SIZE OF ABALONE CAUGHT IN A NEW-SOUTH-WALES FISHERY, Fishery bulletin, 95(3), 1997, pp. 403-413
The fishery for blacklip abalone, Haliotis rubra, is one of the most v
aluable in New South Wales, Australia. An important part of the stock
assessment process for this fishery is to quantify temporal changes in
mean size and size structure of abalone in the landed catch. Variatio
n in abalone growth over small spatial scales in this fishery and diff
erences in harvest strategy among different divers result in large var
iations in sizes of abalone landed. Monte Carlo simulations were used
to investigate the influence of these sources of variation on estimate
s of mean size and size structure. Different sampling scenarios were c
onsidered-from random sampling of all diver-days to a more realistic s
cheme where abalone were subsampled both within and among diver-days.
For a given total number of abalone measured, error in estimated mean
size and size structure declined asymptotically with increasing number
s of diver-days. By measuring at least 1,500 abalone from 100 diver-da
ys, reliable estimates of size structure and mean size of abalone in t
he catch for the whole fishery were produced. This conclusion was robu
st with respect to the number of diver-days in the fishery. Estimated
sampling intensity and probabilities of detecting differences based on
simulated variances for the whole fishery are provided.