biomass from an ecosystem based fisheries management ... pope_mareframe_… · ssb cod ssb haddock...
TRANSCRIPT
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
0.30
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
200
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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