Some insights into the estimability of non-linear dependence of CPUE on abundance in orange roughy fisheries, based upon a simple age-aggregated production model

Butterworth, Doug S; Brandão, Anabela

Some insights into the estimability of non-linear dependence of CPUE on abundance in orange roughy fisheries, based upon a simple age-aggregated production model

Working Paper

2005

Publisher

University of Cape Town

Department

Marine Resource Assessment and Management Group

Faculty

Faculty of Science

Abstract

A simple Schaefer-like production model is used in simulations to assess the potential benefits or otherwise of attempting to estimate the extent of nonlinearity in a CPUE-abundance relationship (reflected by the parameter β). The resource situation considered is similar to that analysed by Hicks (2005), though this paper evaluates only estimation based upon CPUE data alone. Simulations are conducted for three pre-exploitation values of orange roughy abundance, which correspond to a resource which at present is either still declining, is approximately stable, or is increasing slightly. CPUE data are generated for five different values of the β parameter, and estimators which either fix this value, or try to estimate it from the fit of the population model to the CPUE data, are considered. An initial impression of the results obtained for estimates of the initial biomass, current depletion and current replacement yield for the simulated resource is that, in terms of root -meansquare errors, estimating β can achieve smallish gains in some circumstances, but leads to much larger losses in others.

Reference:

Collections

Working Papers

Full item page