biomass from an ecosystem based fisheries management ... pope_mareframe_… · ssb cod ssb haddock...

Biomass From an Ecosystem Based FisheriesManagement Perspective.

By John PopeNRC (EUROPE) LIMITED

Biomass is rather likemoney in a Bank

Basics

In the long run Biomass declines as fishing increases.

Catch at first increases and then declinesas the amount of fishing increases.

Note on tradeoffs

We need Spawning stock to spawn the nextgeneration

Picture of fish eggs From Cover of Fish Reproductive Biology, Wiley-Blackwell

Biomass Reference points(From ICES introduction to advice)

Bpa

Spawning Stock Biomass

Blim BMSY

But Big Fish Eat Little Fish.Moreover, Little Fish may eat the young of Big Fish

Contrasting Models with and without Predation

Multispecies concerns

SandeelSprat

GreyGurnard

To Help we have made aninteractive multispecies model ofthe North Sea suitable forstakeholders use.

We will beholding adecision makersworkshop usingthis in Brusselsin June.We hope someof you may beable to attend.

Main Points

It is very important to avoid spawning stocks becoming too lowSo avoid Blim.But big fish eat small fish.So Predation Mortality increases at high predator biomassHence MSY Biomass estimates may be unrealistically highFor the long term we need to start managing the whole ecosystem

rather than single stocks.For Ecosystem Based Fishery Management MSY is probably not a

sensible societal objective.

My Acknowledgements are due to DG RESEARCH for funding and toICES, MAREFRAME and to the North Sea andPelagic Advisory Councils for help, advice andencouragement.

The Remaining Slides are for discussion points

Results for North Sea Cod from ICES Website

Decline in Recruitment of the Newfoundland Cod

Demersal CFP Compliant criteria

0.00

0.10

0.20

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0.40

0.50

0.60

Fcod F haddock F saithe F whiting F plaice F sole

Fishing Mortality Rate

BAU MMEY Solution MAX GVA Maximum value

Conservation MEY Pel MEY Dem SS Fmsy

0

50

100

150

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SSB cod SSB haddock SSB saithe SSB whiting SSB plaice*0.1 SSB sole

SSB (NB Plaice scaled to improve contrast)

BAU MMEY Solution MAX GVA Maximum value

Conservation MEY Pel MEY Dem Blim

SS MSY Btrigger SS Bmsy*

Note These are all compared to the existing single species reference points. Itis possible that some future CFP might use Multispecies reference points.

NORTH SEA GREEN MODEL

Spawning Stock Biomass (SSB)and Total biomass