shellfish culture and nature conservation
DESCRIPTION
SHELLFISH CULTURE AND NATURE CONSERVATION. Aad Smaal Institute for Marine Resources and Ecosystem Studies Yerseke, NL. IMARES: NEW INSTITUTE Former Fishery Institute merged with 2 other groups ENVIRONMENT FISHERY AQUACULTURE Shellfish Research, Yerseke - PowerPoint PPT PresentationTRANSCRIPT
Centre for
Shellfish Research
SHELLFISH CULTURE AND
NATURE CONSERVATION
Aad Smaal
Institute for Marine Resources and Ecosystem Studies
Yerseke, NL
Centre for
Shellfish Research
Delta
North Sea
IMARES: NEW INSTITUTE
Former Fishery Institute merged
with 2 other groups
ENVIRONMENT
FISHERY
AQUACULTURE
Shellfish Research, Yerseke
- population dynamics
- carrying capacity
- culture innovation
Centre for
Shellfish Research
PROBLEMS IN CULTURE AND CONSERVATION
• Shellfish culture / fisheries always has an impact on the
ecosystem
• Shellfish culture occurs often in areas that are now
protected for nature conservation
• What are the impacts, positive / negative, acceptable ?
• Source of conflicts between stakeholders
• Role of science / politics / governments
Centre for
Shellfish Research
OUTLINE
• ROLE OF SHELLFISH IN THE SYSTEM
• IMPACTS OF CULTURE
• REGULATION
• STAKEHOLDERS
• CONSERVATION and EXPLOITATION
Centre for
Shellfish Research
Food
Habitat Feedbacks
ROLE OF SHELLFISH
Oosterschelde case: storm surge barrier
Analysis of the role of mussels in the ecosystem:
benthic tunnels, mesocosms, models
• Residence time >• Water transparency >• Nutrient loads <
• Internal nutrient cycles more important• Adaptation of phytoplankton• Maintenance of primary production
Prins & Smaal, 1994; Prins et al, 1998; Smaal et al, 2001
Nutrient (N) regeneration through direct excretion + biodeposit mineralization up to 40 % of total N regeneration
Through grazing increase in phyto plankton turnover ; optimal mussel growth at intermediate biomass
Bottom-up control at low mussel density and top-down control at high mussel density
Centre for
Shellfish Research
FUNCTIONAL ROLE:
• Grazing of phytoplankton
• Production of biodeposits
• Regeneration of nutrients
• Promotion of algal growth
• Stabilization of the ecosystem
feedbacks through filter feeding
Centre for
Shellfish Research
FOOD FOR BIRDS:
• shellfish beds are essential as food source for waders and diving ducks
• shellfish stocks may show large variability in time
• birds may switch prey
• collapse of both mussel and cockle stocks caused problems in Wadden Sea and Wash in ’90
0
50
100
150
200
250
mln kg fresh
1971 1974 1977 1980 1983 1986 1989 1992 1995 1998
0
1
2
3
4
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000
bestand droog
Mussel stock(index)
Eider duck mortality
1991
Cockle
stock
Call for shellfishery policy
0
100
200
300
400
500
mln kg fresh
1990 1992 1994 1996 1998 2000 2002
BSF dynamics
mussel
macoma
cockle
0
50000
100000
150000
200000
250000
300000
350000
75767778798081828384858687888990919293949596979899000102
Oystercatcher decrease after
low shellfish stocks 1996 due
to severe winter
Centre for
Shellfish Research
CONCLUSION FOOD
FOR BIRDS
• Shellfish is major resource
• Minimum stock required for longterm maintenance of
bird populations
• high shellfish dynamics sometimes don’t match bird needs
• call for protective measures
0
20
40
60
80
100
120
140
160
180
51 55 59 63 67 71 75 79 83 87 91 95 99
mln kg fresh
Import
Wad
Delta
0
20000
40000
60000
80000
100000
77 80 83 86 89 92 95 98
MILJOEN KG VERS
vd
ws
os
wad
HARVEST IN NL FROM
CULTURE AND FISHERY
MUSSEL: 100 MLN KG
COCKLE: 20 MLN KG
OYSTER: 3 MLN KG
00.5
11.5
22.5
3
mln kg
52 57 62 67 72 77 82 87 92 97
oyster production
Crassostrea
Ostrea
ROLE AS HABITAT
Biocoenose (Mobius, 1880)
Epibenthic shellfish beds form structures
nr of species > 150 (Sayer, 2002)
Biodiversity higher in sublitoral (Buchsbaum & Sayer, 2003)
Impact of culture ?
Centre for
Shellfish Research
IMPACTS OF SHELLFISH CULTURE
Feedbacks
impact on Stocks
Food
Habitat direct:
bottom culture – infauna (clams, cockles)
- epifauna (mussels, oysters)
indirect: suspended culture
WILD LITORAL STOCK
WILD SUBLITORAL STOCK
CULTURE PLOTS
SHELLFISH FLOW
natural spatfal natural spatfal
Seed fishery
harvest
RESULT: NET INCREASE OF BIOMASS
IMPACTS on STOCKS
IMPACTS on STOCKS
Case study : Wadden Sea bottom culture
Model calculation wild beds vs culture plots:
Musselseed plots/wild - Growth 1.7 x higher
- Density 0.6 - Mortality 0.8
Net result: stock – harvest 1.15: 15 % more biomass
Note: Carrying capacity problems due to overstocking
IMPACTS on HABITAT
Bottom culture:
• Culture of mussels and oysters
on bottom plots,
frequent fishery activities
effects on biodiversity depend on
local conditions
• Culture / fishery of infauna :
sediment change ?
mortality of bycatch ?
less spatfal ?
many studies
controversial issue
ban on cockle fishery Waddensea 2003
Wild
bed
Cultureplots
muddy sub
(Von Westphalen, 2005)
sand
(van Gils et al, 2004)
Impact of cockle fishery
Seed fishery on wild beds
Mussels : focus on unstable beds
Littoral : experimental seed fishery
to test impact on stability:
no net effect of fishery on seed mussel density
Sublittoral : research topic
Major issue in actual discussion in NL
IMPACTS on HABITAT
Suspended culture:
• Sediment deposition
depomod application
mostly for fish farming
useful for shellfish
(no external input, only concentrating material)
• Benthic community
various studies: (Grant et al, 2005; DEPOMOD)
- local scale effects
- depend on hydrodynamics, site etc
- can both enhance or reduce species nr
Centre for
Shellfish Research
SUMMARY OF IMPACTS
Stocks: AVERAGE INCREASE
Habitats: bottom culture / seed fishery
epifauna BIODIVERSITY
HABITAT COMPLEXITY
infauna SEDIMENT/BENTHOS
suspended culture SEDIMENT/BENTHOS
POLICY & REGULATION
NATIONAL: policy document 2004
“Space for harvest”
- sustainable use
- innovation by industry, less impacts
- closed areas
EU: Bird and Habitat Directive (implementation NL 2004)
- For nature conservation areas
- in many cases shellfish culture areas
- permit required for each seed fishery period (2x p yr)
- industry has to perform an appropriate assessment
of possible impacts on management objectives
- permits can be stopped by court after objections
STAKEHOLDERS
INDUSTRY RESPONSE
• triple P approach : Profit, Planet, People
= continuous improvement
= planning + evaluation + research
= draws up fishing plans,
= uses black boxes onboard fishing vessels
= register activities in an electronic logbook
• Develop an innovation agenda
• Stakeholder involvement
• Setting up research: innovation
continuous improvement
ProfitProfit
PlanetPlanetPeoplePeople
INNOVATION: life cycle control
PRODUCT
HATCHERY
SEED
COLLECTORS WILD SEED
FISHERY
IMOZA - Doove Balg
IMOZA - Verversgat
IMOZA - Vlieter
IMOZA - Stompe
IMOZA - Malzwin
IMOZA - Bollen
Wietex - Texelstroom
Wietex - Oergat
Wietex - MalzwinPD - Malzwin
West 6 - Malzwin
Zaadinvang locaties
Kustlijn
Laagwaterlijn
Naam: Produs 1c
Auteur: J.M.D.D. Baars
Archief: q:/projects/kleine_opdr/pk05 Datum:juli 2005
Centrum voor Schelpdier Onderzoek
NederlandsInstituut voor
Visserijonderzoek
MUSSEL SEED HATCHERY/
COLLECTORS NURSERY
STAKEHOLDERS
NGO RESPONSE
• objected against seed fishery permits
• case in court in spring and autumn
• court decision: fishery could go on
BACKGROUND
Nature conservation areas should not be exploited
Editorial in PloS Biology of Nov 14, 2006 based on
culture
conservation restoration
X
?
NATURE CONSERVATION STRATEGIES
• Protection against adverse impacts
• Conservation of non-impacted areas
• Prevention of new impacts
• Habitat restoration
• Habitat creation
• Multi-functional use
• Sustainable use
exclusion
mitigation
integration
Dynamic / control
Static / spontaneous
NATURE CONSERVATION = CULTURAL ISSUE
PARADOX OF EXTENSIVE EXPLOITATION
• extensive exploitation is part of nature and contributes to
ecosystem processes (food, feedback, habitat)
• exploitation depends on natural dynamics and farmers
want to become less dependent
• nature conservationists want to restrict exploitation
• 2 forces in the direction of intensification
• more intensive culture in existing areas calls for more
criticism
• loss of extensive culture
• future need for shellfish restoration
Centre for
Shellfish Research
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