An interactive multispecies model of the North Sea suitable for stakeholders use.

John Pope

Multispecies Models For Concerns

Co-creation =

Requirements

Its Structure should:-• Take Account of Species Interactions and Technical

Interactions• Handle the main range of TAC species.• Allow fishing to be changed in realistic waysIts Outputs should include the important trade offs:-• Species Yield• Fleet Economics• Social implications• Ecosystem EffectsMost of all it MUST BE:-• Transportable, Easy to understand and Responsive.

To Be used by Stakeholders Model Needs to be Transportable, Easy to understand and Responsive.

SO! Model Based On EXCEL Using Matrix Algebra

e.gMulti-species

SchaeferSimple Interactive Overview

The Fleet Problem:- e.g. Roundfish

Problem is lots of fleets predominantly catch roundfish but in different proportions and with different catch of other Species.

It is even worse for Flatfish Fisheries!

Solution is Changing the amount of Fishing by species (vertical sliders) - here cod fishing reduced to 80% of

BUT Obeying Fleet CatchConstraints (Horizontal Sliders modify)

However, it constrains what is possible (red line) given fleet behaviour.

But, you have a say on the constraints!

Simple Interactive Overview

Hence - Model lets you change

Fishing Mortality as you like (blue line)

Results I

Bottom Disturbance Charismatic by catch0.87 1

Results II

Where to next

Check validity of Schaefer approximation. Approach• Fit to wider range of output of SMS and of other Models.

Get it to handle Mesh Change. Possible approach • Use Pope 1989 method of estimating Jacobian Matrix of

surface from partial F’s and M2’s

Transitional Behaviour. Possible approach• Use steady state parameters as first approximation then

use Multispecies Schaefer differential equation to fit time series with modest changes.

Farewell and Adieu!

• But try out the green model and suggest improvements and discuss it and the other models (see below) with me.

• My Thanks to MAREFRAME, NSAC, PELAC and WGSAM Colleagues for help and to the EU’s 7 Framework programme who funded this project.

How to tackle the Amber Model?

Broad Requirements as Green Model but with area and size. • Need to include possibility for area closure• Need to include some species as multiple stocks (e.g.

Nephrops)

Possible Approach.• Attempt an area and sized based model based upon SMS

or similar overall model results. These would then be partitioned by fleet rectangle data and by survey data.

• Yes I know this sounds Heroic!

How to tackle the red model?

• Use previous two models to see when and where regulations cause problems.

• Collaborate closely with SAF21 Project (Social Science Aspects of Fisheries for the 21st Century ).

• Prayer