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SHELLFISH CULTURE AND NATURE CONSERVATION

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

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SHELLFISH CULTURE AND NATURE CONSERVATION

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  1. SHELLFISH CULTURE AND NATURE CONSERVATION Aad Smaal Institute for Marine Resources and Ecosystem Studies Yerseke, NL

  2. IMARES: NEW INSTITUTE Former Fishery Institute merged with 2 other groups ENVIRONMENT FISHERY AQUACULTURE Shellfish Research, Yerseke - population dynamics - carrying capacity - culture innovation North Sea Delta

  3. 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

  4. OUTLINE • ROLE OF SHELLFISH IN THE SYSTEM • IMPACTS OF CULTURE • REGULATION • STAKEHOLDERS • CONSERVATION and EXPLOITATION

  5. ROLE OF SHELLFISH Food Habitat Feedbacks

  6. Oosterschelde case: storm surge barrier • Residence time > • Water transparency > • Nutrient loads < • Internal nutrient cycles more important • Adaptation of phytoplankton • Maintenance of primary production Analysis of the role of mussels in the ecosystem: benthic tunnels, mesocosms, models Prins & Smaal, 1994; Prins et al, 1998; Smaal et al, 2001

  7. Nutrient (N) regeneration through direct excretion + biodeposit mineralization up to 40 % of total N regeneration

  8. Bottom-up control at low mussel density and top-down control at high mussel density Through grazing increase in phyto plankton turnover ; optimal mussel growth at intermediate biomass

  9. FUNCTIONAL ROLE: • Grazing of phytoplankton • Production of biodeposits • Regeneration of nutrients • Promotion of algal growth • Stabilization of the ecosystem • feedbacks through filter feeding

  10. 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 problemsin Wadden Sea and Wash in ’90

  11. Mussel stock(index) Cockle stock Eider duck mortality 1991 Call for shellfishery policy

  12. Oystercatcher decrease after low shellfish stocks 1996 due to severe winter

  13. 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

  14. HARVEST IN NL FROM CULTURE AND FISHERY MUSSEL: 100 MLN KG COCKLE: 20 MLN KG OYSTER: 3 MLN KG

  15. 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 ?

  16. IMPACTS OF SHELLFISH CULTURE Feedbacks impact on Stocks Food Habitat direct: bottom culture – infauna (clams, cockles) - epifauna (mussels, oysters) indirect: suspended culture

  17. IMPACTS on STOCKS SHELLFISH FLOW natural spatfal natural spatfal WILD SUBLITORAL STOCK WILD LITORAL STOCK harvest Seed fishery CULTURE PLOTS RESULT: NET INCREASE OF BIOMASS

  18. 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

  19. 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 sand Cultureplots muddy sub (Von Westphalen, 2005) Impact of cockle fishery (van Gils et al, 2004)

  20. 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

  21. 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

  22. SUMMARY OF IMPACTS Stocks: AVERAGE INCREASE Habitats: bottom culture / seed fishery epifauna BIODIVERSITY HABITAT COMPLEXITY infauna SEDIMENT/BENTHOS suspended culture SEDIMENT/BENTHOS

  23. 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

  24. Profit continuous improvement People Planet • 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

  25. HATCHERY PRODUCT SEED COLLECTORS WILD SEED FISHERY INNOVATION: life cycle control

  26. MUSSEL SEED HATCHERY/ COLLECTORS NURSERY

  27. 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

  28. Editorial in PloS Biology of Nov 14, 2006 based on culture conservation restoration X ?

  29. 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 Static / spontaneous exclusion mitigation integration Dynamic / control

  30. NATURE CONSERVATION = CULTURAL ISSUE

  31. 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

  32. * Join us in the 10th ICSR07 In Zeeland *

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