Software for estimating potential yield under certainty

Background

To achieve sustainable and precautionary fisheries management, as promoted by FAO guidelines, managers need reliable estimates of the potential yield of their fisheries. Yield estimates will, however, be affected by uncertainties in the biological parameter estimates used, which need to be quantified. Furthermore, many fish stocks show considerable interannual variability in recruitment, which implies alternative targets to maximum sustainable yield are required for precautionary management.

Methods for quantifying uncertainty, and determining alternative management targets are available, but usually require statistical expertise, and usually have high data requirements. There is therefore a need for a robust, easy-to-use method for estimating potential yield (or, alternatively, yield or yield-per-recruit reference points) that would be accessible for fisheries managers in developing countries.

Approach

The project developed a user-friendly, Windows-based software package for fisheries managers to use in selecting and setting appropriate yield and effort targets. Users are able to specify levels of uncertainty in each of their biological input parameters, and the level of inter-annual variability in recruitment. Results are presented in terms of frequency distributions, rather than single values, showing the level of uncertainty. Forward projections allow the user to evaluate different management options.

The software has an extensive online help system, and includes a detailed tutorial, which gives an example analysis of data from an Indian Ocean snapper fishery.

Findings

The Yield software successfully developed in this project will enable fisheries scientists in developing countries to provide reliable advice for fishery management that properly accounts for uncertainties due to variable recruitment and lack of knowledge of some key biological parameters. From the outputs of the software, this advice can be presented in terms of target (potential target values to aim for in setting appropriate levels of fishing mortality) and limit (values of fishing mortality that should not be exceeded) reference points. Such reference points are required by FAO guidelines and a number of international agreements. The improved scientific advice will considerably enhance the likelihood of sustainable management of vital fisheries resources. A number of training courses have also been delivered and copies of the training materials may be downloaded from Project R8468 Publications Page.