Work package 7.
GLM type analysis to “export” ecosystem Fmsy
General linear Models (GLM) models will be used to “export” ecosystem Fmsy from stocks where these available from multispecies and ecosystem models and density dependent growth and maturity (and cannibalism) studies, to stocks where such models and studies are not available. The link between the stocks is envisioned to be life history parameters and species groups.
The candidate life history parameters for such analysis are Lmax, age at 50% maturity, Von Bertalanffy K, Steepness in Stock-recruitment curves, relative increase in weight from age-at-“50% maturity” to age-at-“50% maturity” +1year. As we here are dealing with data rich stocks, such data are easily available or can easily be calculated.
A multiplicative model like, will be applied:
Log(Fmsy (s)) = a +“Species group”(s) + L(s)
Where s is a given stock, a the intercept, “Species group” is species group like for instance “cod” or “plaice”, and L is the life history parameter, for instance Lmax. Fmsy will be expressed in the “common currency” unit. Various model alternatives will be developed and tested using the traditional ways of selecting the most appropriate one. The parameters from the final model will be used to obtain ecosystem Fmsy for those stocks which do not have such values, i.e. for the “export”.
Key persons: Henrik, Bjarte, Gunnar