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

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

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

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

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 Seed fishery harvest RESULT: NET INCREASE OF BIOMASS IMPACTS on STOCKS

Case study : Wadden Sea bottom culture Model calculation wild beds vs culture plots: Musselseed plots/wild - Growth1.7 x higher - Density0.6 - Mortality0.8 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 Cultur eplots 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 Profit PlanetPeople

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

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 conservationrestoration 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

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