duurzame vis hoe gaat het met de visbestanden? 16 januari, jan jaap poos (imares)
TRANSCRIPT
Duurzame vis
Hoe gaat het met de visbestanden?
16 Januari, Jan Jaap Poos (IMARES)
2048
Text slide
3
Global loss of species from Marine Ecosystems
Worm et al 2006 in Science
Cumulative
Annual
“There will be a point in the future where we will run out ...”
Commentaren op “2048” schatting
Branch 2008 in Marine Policy
“[...] even if all fisheries collapsed at least once, 50–55% would be recovered in any given year.”
Hilborn and Branch 2013 in Nature
It is misleading to use catch data to assess the health of fish stocks
Hoe gaat het met de visbestanden?
Analysis of “2048” in scientific literature
Wat zijn dan de regels?
Hoe gaan we daar in Europa mee om?
Froese and Proelss 2010 in fish and Fisheries
“[...] if European Governments are serious about meeting their obligations to [...] the Johannesburg Plan of Implementation[...] they will have to reduce drastically fishing pressure and halt fishing completely on some of the European stocks.
CFPVisserijbeleid in Europa geformuleerd in Common Fisheries Policy. De regels voor beheer van visbestanden in Europa
Population models, MSY &
overfishing
Generiek populatiemodel
Population
Growth
Recruitment
Natural Mortality
Fishing+ -
0 5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
1.2
Generiek populatiemodel
Time
Bio
mass
Exponentiele groei
Dichtheidsafhankelijke groei en sterfte
Generiek populatiemodel
Carrying capacity K, Bmax
0 5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
1.2
Bio
mass
Time
2BK
rrB=
dt
dB
K
BrB
dt
dB1
B = population biomasst = timer = intrinsic population growth rateK = carrying capacity
Generiek populatiemodel
0 5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
1.2
Time
Bio
mass
Carrying capacity
Maximum population growth
Generiek populatiemodel
Carrying capacity K
0 5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
1.2
Bio
mass
Time
Max population growth
2BK
rrB=
dt
dB
We know population growth:
At what biomass do we find maximum growth?
Generiek populatiemodel
0 5 10 15 20 25 300
0.2
0.4
0.6
0.8
1
1.2
Time
Bio
mass
Carrying capacity
Maximum growth
Generiek populatiemodel
Biomass
Popu
lati
on
gro
wth
Max population growth
0 0.2 0.4 0.6 0.8 10
0.91.82.73.64.55.46.37.28.1
99.9
K
Van populatie groei naar surplus productie
Y
B = population biomasst = timer = intrinsic population growth rateK = carrying capacityY = Yield (also called catches)
growthmortality Yield
2BK
rrB=
dt
dB
Biomass
Popula
tion g
row
th
Max pop growth
0 0.2 0.4 0.6 0.8 10123456789
10
Schaeffer model
Populatie in evenwicht als Yield = groei
Y2BK
rrB=
dt
dB
Biomass
Popula
tion g
row
th
Max pop growth
0 0.2 0.4 0.6 0.8 10123456789
10YBK
rrB=
20
2BK
rrB=Y
= maximum surplus
=Maximum sustainable yield
Visserij druk
Y
B = population biomassY = Yield (also called catches)q = catchabilityE = fishing effort
2BK
rrB=
dt
dB
Biomass
Popula
tion g
row
th
0 0.2 0.4 0.6 0.8 10123456789
10
qEBBK
rrB=
dt
dB
2
0 0.2 0.4 0.6 0.8 10123456789
10
Yield
Fishing effort
Eindresultaat: de yield curve
0 0.2 0.4 0.6 0.8 10
0.51
1.52
2.53
3.54
4.55
5.56
6.57
7.58
8.59
9.510
Yield
Fishing effort (or fishing mortality)
Eindresultaat: de yield curve
0 0.2 0.4 0.6 0.8 10
0.51
1.52
2.53
3.54
4.55
5.56
6.57
7.58
8.59
9.510
Yield
Fishing effort (or fishing mortality)
FMSY
costsFisheries “want”
to go here
FMEY
“Yield curves” voor visgemeenschappen
25
Worm et al. 2009 in Science
biodiversity is maintained at low exploitation rate, maximum catch is maintained at intermediate exploitation rate, and high employment is often maintained at intermediate to high exploitation rate”
Where do we stand
26
So where do we stand?
27
Worm et al. 2009 in Science
Global analysis of 166 stocks
For 63% of the examined stocks biomass has dropped below the traditional single-species management target of MSY, that is, B < BMSY. About half of those stocks (28% of total) have exploitation rates that would allow for rebuilding to BMSY
Hoe gaat het in Europa?
28
Fernandes and Cook 2013 in Current Biology
Analyse visbestanden NO AtlanticA) Pelagische vis (haring, makreel, sprot, ...)B) bodemvis (schelvis, koolvis, wijting, ...) C) platvis (schol, tong, heilbot, ...);D) kabeljauwbestanden.
Wat is het effect van verlaging visserijdruk?
29
Fernandes and Cook 2013 in Current Biology
Afname visserijdruk, toename biomassas
Situatie is anders in de Middellandse zee
Vasilakopoulos et al. 2014 in Current Biology
[...] the CFP has not succeeded in improving the state of European Mediterranean commercial fish stocks over the past two decades
“data limitations, low levels of compliance, and poor enforcement”
Visserijdruk Biomassa
Economy
Wat kan er mis gaan: beheerscyclus
onderzoek:Dynamiek van• visbestanden• Ecosystemen
visserij:• vangsten• Inspanning• Aanpassen aan
beheer
beheer:• reguleren• implementeren
advies
Gegevens
regels
Plaice: landings
0
50
100
150
200
1977 1982 1987 1992 1997
Th
ou
sa
nd
to
nn
es
official estimated
Plaice
0
50
100
150
200
1977 1982 1987 1992 1997
Th
ou
sa
nd
to
nn
es
recommended agreed
visserij:
beheer:
onderzoek: incorrect
assessment Plaice Sub-area IV (North Sea)
0
50
100
150
200
250
300
350
400
450
500
1980 1985 1990 1995 2000 2005
SSB ('000 tonnes)
Wat kan er mis gaan: beheerscyclus
De CFP (en certificering)
33
De Common Fisheries Policy
34
Environmentally sustainability while achieving economic, social and employment benefits
Apply the precautionary approach The maximum sustainable yield exploitation rate shall be achieved by 2015 where possible and at the latest by 2020 for all stocks
implement the ecosystem-based approach to minimize negative impacts of fishing on the marine ecosystem
Laatste hervorming CFP in 2013
35Uit Smith 2013 in Current Biology
Certificering
36
MSC
RFS
Viswijzer
Friends of the Sea
Waddengoud
Marine Stewardship Council
37
MSC Fisheries standard
MSC chain of custody standard
Third party certification
Reviewing standards
Principle 1: sustainable fish stocksFishing activity must be at a level which ensures it can continue indefinitely
Principle 2: Minimising environmental impact
Fishing operations must be managed to maintain the structure, productivity, function and diversity of the ecosystem
Principle 3: Effective management The fishery must comply with relevant laws and have a management system that is responsive to changing circumstances
Marine Stewardship Council
MSC Fisheries standard
MSC chain of custody standard
Third party certification
Reviewing standards
Also the MSC label is hotly debated:
Jacquet et al. 2010 in nature
“The MSC is growing rapidly; the organization is also rapidly failing on its promise.”
“In our view, the certification system creates a potential financial conflict of interest, because certifiers that leniently interpret existing criteria might expect to receive more work and profit from ongoing annual audits.”
Kaiser and Hill 2010 in Nature
“We believe that the MSC process has refocused the behaviour and attitudes of fishermen in these areas, and has delivered conservation benefits more effectively than formal non-participatory legislation would have.”
Thank you