Work package 4.

Surplus production model estimates of Fmsy

The so-called summary tables from the ordinary assessments of the stocks, will be used in ordinary surplus productions models (SPMs). These tables contain time series of catch, SSB, and F. F can be used as a measure of fishing effort and SSB as an index of stock size. The software package ASPIC can easily handle these kind of data.

SPMs are not working well if the is no dynamic range in the time series data. Furthermore, in cases where there are large dynamic ranges in data SPM does perform well neither, if these variations is due to environmental variations and not varying fishing pressure. F has to be the main driving force for the variation in the stock.

One task is therefore to define criteria for selecting stocks where SPMs are supposed to work well.

The other task is of course to perform the SPMs and extract the Fmsy estimates. Selecting the shape of the production curve (whether Bmsy/B0 is 0.5 as in Schaefer or 0.33 as in Pella-Tomlinson, or 0.4 in Thorson et al. (2012, Can. J. Fish. Aquat. Sci. Vol. 69, 2012), or variable by species) is a point to be worked on in the project.

Finally, performing the actual analysis on around 30 stocks, expected to be suitable for SPMs, is not a trivial work load.

Key Persons: Henrik, Ray, Jan, Gunnar