Stock assessment approach for the Napoleon fish, Cheilinus undulatus, in Indonesia
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A stock assessment approach for the Napoleon fish (humphead wrasse), Cheilinus undulatus, is presented as a tool for determining sustainable catch levels of the species. The model was developed primarily for application in Indonesia and in collaboration with the Research Center for Oceanography, Indonesian Institute of Sciences (LIPI). The model can be adapted for estimating sustainable catch levels in other countries, if suitable estimates of reef area and fish densities are available . The approach is composed of a population model and a method for estimating stock density based on underwater visual surveys, allows for the representation of "grow out" of net-caged animals, a significant part of the trade, includes the ability to account for uncertainty in most of the parameters of the model, and can compute a sustainable catch (and its associated uncertainty) corresponding to a user-specified level of fishing mortality. The resultant model is implemented using Micros oft EXCEL and Visual Basic, with a graphical user interface for easy use (the EXCEL spreadsheet is included in the <b><a href="https://www.fao.org/fishery/static/docrep/c1023/Napoleon.xls" class="external-link-new-window" title="Opens external link in new window" external="1">CD-Rom</a></b> provided with this Fisheries Circular). Sustainable fishing mortality rates for the species in Indonesia can be estimated based on commonly used biological reference points (e.g. FMSY; F20%). Results of sensitivity tests indicated that the relationship between stock and recruitment remains the major uncertainty affecting the estimation of sustainable fishing rates. Preliminary estimates of export quotas for Indonesia are provided taking into account the official statistics on the volume of domestic catches and estimated illegal and unreported exports. Estimated export quotas were highly sensitive to the estimated habitat area suitable for the species, which highlights the need for more accurate estimates of reef habitat areas in Indonesia. Quotas depend heavily on successful implementation and are one of several possible approaches to achieving sustainable exports of a CITES Appendix II listed species.