Work package 3.
Compile ecosystem and multispecies estimates of Fmsy.
For the set of stocks selected for the current project (Table 1) compile the existing Fmsy values that takes into account cannibalism (CAN) and density dependent recruitment (R), growth (G) and maturity (MAT). Assume current stocks sizes for interacting species. The new Ecosystem Fmsy values are only intended to be valid for about 5 years, because for longer time periods interacting stocks can probably not be regarded as reasonably constant in size. This means that after 5 year the current compilation will have to be renewed.
Models relevant for this work are: SMS, MSVPA, 4M, Noel Holmgreen’s Baltic model, Ecopath with Ecosim (EwE), Gadget, Atlantis, Andersen&Ursin’s North Sea model, etc.
Species interactions like a negative one between cod and shrimps, between cod and capelin, between NOSS herring age 1-3 and capelin, between predators and forage fish in general, between cod and lobsters, between cod and Norway lobster, will only be dealt with verbally or schematically, for instance as a general secondary benefit of managing predatory stocks at moderate size levels compared to at high size levels.
While Fmsy provides reference points for fisheries on a stock by stock basis that may optimize sustainable catch levels, it is clear that there can be tradeoffs between fisheries that may impact what is actually achievable (Walters et al. 2005). What will happen if Fmsy is applied for all populations in an area over time? Will the reduced abundance of forage fish impact the achievable catch levels for the predatory fishes that rely on the forage fish?
To evaluate this calls for the evaluation of tradeoffs, and a suite of alternative models will be applied to address the question, ranging from qualitative impacts evaluated from PROST, to quantitative impacts from alternative models such as listed in the table above.
Key persons: Villy, Daniel, Jeremy, Petur, Jan, Gunnar, Bjarte, Ray.