Perspectives for flat oyster reef restoration

Dutch experiences with shellfish & eco-engineering

November 2012,

Christiaan van Sluis, Jeroen Jansen and Aad Smaal

Why restoration?

Provision of ecosystem services through:

• Filter feeder: filtration + nutrient regeneration

• Reintroduction reef habitat by ecosystem engineer (N2000)

• Fish & bird feed: oysters and associated species

• Potential for sustainable exploitation

Stimulation of flat oysters makes sense:

- natural, cultural & culinary heritage

Daniel Ridgway Knight:

The oyster gatherer

Regime shifts in changing ecosystems

Questions:

- Where there oysters before

- Why oysters disappeared?

Can we find and

reduce barriers

to reintroduction?

Scheffer et al. 2001

Ecosyste

m s

tate

Unknown environmental conditions

!

Why am I (I-mares) here?

Some NGO’s support restoration of flat oyster beds

Group of people willing to contribute

IMARES works on shellfish restoration and culture:

● Mussel bed monitoring and restoration

● Flat oyster aquaculture in the Dutch Delta

● Building with Nature - ecosystem engineering

1) MUSSELWAD –monitoring existing beds

Research: Why mussel beds disappear/remain over years?

Understanding bank development and survival through:

Hydrodynamics, erosion by waves, wind and tides

● By dissipating wave action, mussels on the edge

project mussels in the middle (Donker et al,

submitted).

● Mussel banks originate at low dynamic sites

How does predation determine survival?

2) Mussel bed restoration for birds

1) Seeding on existing and created littoral oyster banks

● Oysters occur in most mussel banks

● Oysters protect mussels against erosion

● Oysters form predation refuges for small mussels

● Also without mussels oysters are foraging ground

2) Seeding on former littoral mussel banks

Monitoring mussel bed condition

● bed density and mussel density

● Individual mussel condition, foraging birds, waves, current velocities

Flat oyster culture in the Dutch Delta

How to ensure survival and growth:

Expert knowledge of:

● Spat collection

● Larval assessment

● Disease monitoring with CVI

● Development of genetic identification

● Hatchery capacity & Purification breeding

IMARES participates in local shellfish culture group

Shellfish knowledge groups - Oysterculture

Activities

Share: Qualities, characteristics and skills

Construct alliances with others partners

Give trust (and hence receive it)

Results:

Increased rentability

Maximized “learning from each other”

with shared profits

Good functioning and innovating shellfish industry

Industry

Innovators

(Leads)

Science

(supports and

facilitates)

Innovation

Knowledge transfer

Government

(Facilitates)

Building with Nature – shellfish reefs

Loss of intertidal flats due to morphological misbalance

Question:

Can we stabilize intertidal flats with shellfish reefs?

- Morphology

- Biology

- Governance

Oyster reef creation in the Southwest Delta

Using shellfish reefs against erosion of intertidal flats

Experience

Height in the intertidal

Fouling

Recruitment

ECOBAS Bangladesh:

Eco-engineered coastal defence integrated with

sustainable aquatic food production

More lessons on turbidity, inundation time and hydrodynamic stress

Building with Nature: lessons learned

Biosphere

Minimum population size for sufficient recruitment: spawning stock biomass (adult females) needed (potentially aquaculture)

Competition: selection of brood stock: adaptive capacity, disease free self-sustaining, competitive (with Pacific oyster)

Fouling

Food availability

Bonamia

Support each life stage

Hydrosphere

Hydrodynamics, currents (flushing of larvae), waves, wind, tides

Temperature (Sensitive, but also adaptive to low temperature)

Nutrients and pollution

Salinity

pH

Turbidity

Contaminants (TBT & Cupper)

Lithosphere and Atmosphere

Presence of hard substrates for settling (Sedentary life)

Substrate within dispersal range

Sedimentation

Silt vs. organic matter

Governance

•Awareness: need for public & stakeholder involvement

•Funding opportunities

•Cost effectiveness: knowledge based approach

•Legislation, sometimes new activities not allowed

•see > 30 recommendations of Ashton & Brown in prep

Discussion

Breaking barriers:

Reason for disappearance.

- Diseases – is this a real obstacle?

- Disturbance – wind parks

- Regime shift (s)? – don’t know

Habitat suitability (4 Spheres)

Governance – policy support