WGMIXFISH holds two meetings: The first meeting (WGMIXFISH-ADVICE) aims to produce mixed fishery projections according to tested methodology and
relating these to each stock’s single-species advice. The second meeting
(WGMIXFISH-METHODS) focuses on advances and additions to the methodology, e.g. new fleet behaviour
or management target ‘scenarios’,
incorporation of uncertainty, or application to new management areas.
WGMIXFISH
uses the Fcube approach (after Fleet and Fishery Forecast), a simple model of
mixed fisheries which can be used to assess the consistency between management
(TAC and/or effort) advice for species caught together, given the availability
and accessibility of data. Currently, forecasts are performed for the North Sea
region using weights of landings and discards and effort disaggregated by fleet
and fishery. A simple linear relationship is assumed between effort and fishing
mortality and status quo catchability assumed in the projections. Forecasts are
produced according to scenarios for what limits the effort in each fleet and
the forecasted catch of each species compared to the single species advice for
TAC. Results are
presented in a unique advice sheet, and those results relevant to each of the species
covered are added to the single species advice sheets.
The
Fcube model in its current form is appropriate for all regions where the
majority of species of commercial interest are assessed quantitatively. Even so,
expansion into new areas usually requires tailoring of the code to accommodate
new species or unique characteristics of the fisheries. There are also many
potential enhancements to the Fcube methodology, e.g. replacing the status quo
catchability assumption with a model component that accounts for changes in
fisher behaviour or technical measures, better addressing stocks lacking a full
quantitative assessment, and accounting for uncertainty in factors such as
stock-recruit relationship, etc. These issues are currently being addressed
within WGMIXFISH.
