1. Assessing and reducing impacts of
aquaculture on marine biodiversity
and ecosystem functioning
Tasman Crowe
University College Dublin

2. Strategic overview of influences of
aquaculture on biodiversity and ecosystems
services in Ireland
• Myriam Callier, Tasman Crowe,
Dannielle Green, Judith Kochmann
Francis O’Beirn & Grainne O’Brien

3. Marine ecosystem services & sectors
Provision of
food Aquaculture
Supporting
industries
Provision of
other biol.
resources Fisheries
Climate
regulation Recreation &
Erosion tourism
control
Pollution • Vital to economy and society, particularly
control
of remote coastal communities.
Aesthetic &
cultural
value
MEA 2005; Govt. of Ireland 2008

4. Aquaculture in Ireland
• Global fisheries in decline, aquaculture
expanding: now provides >50% of seafood
• Aquaculture in Ireland dominated by oysters,
mussels and salmon
– focus on high value, organic/eco-certified products
• Valued at €105 million in 2007
• 2000 jobs, many in rural coastal communities
FAO 2009; Browne et al 2008

5. Aquaculture in Ireland
• Key challenge: finding balance between benefits
of aquaculture and maintaining conservation
status in coastal SACs and SPAs
• Requires good understanding of how
aquaculture interacts with the environment
• Evidence from overseas not always applicable
– Often lower intensity production
– Higher flow than, e.g. Scottish lochs

6. Influences on ecosystems
• Interactions with wild-fisheries resources
– capture of seed mussels
– fish capture for feed production
• Physical changes to the habitat
– addition of structures
• Organic and nutrient enrichment
• Invasive species
– escapes, vectors, facilitation
• Interactions with seals and birds
– positive and negative

7. Influences on ecosystems
• Interactions with wild-fisheries resources
– capture of seed mussels
– fish capture for feed production
• Physical changes to the habitat
– addition of structures
• Organic and nutrient enrichment
• Invasive species
– escapes, vectors, facilitation
• Interactions with seals and birds
– positive and negative

8. Work package 3
Assessing and reducing impacts of aquaculture
on marine biodiversity
4. Test potential impacts of introduced Pacific oysters
 Assess impacts of fish cages and test mitigation strategies
 Provide management recommendations
Tasman Crowe, Myriam Callier,
Dannielle Green, Judith Kochmann,
Francis O’Beirn, Grainne O’Brien

9. Work package 3
Assessing and reducing impacts of aquaculture
on marine biodiversity
4. Test potential impacts of introduced Pacific oysters
 Assess impacts of fish cages and test mitigation strategies
 Provide management recommendations
Tasman Crowe, Myriam Callier,
Dannielle Green, Judith Kochmann,
Francis O’Beirn, Grainne O’Brien

10. Pacific oysters
1950`s
1960`s
1920`s
• Widely introduced for
aquaculture
– in Ireland since 1970s
• Invasive in many
places

11. Potentially significant impacts

12. Pacific oysters in Ireland
Wild oysters now at some sites, therefore research to:
 document and predict spread
- Judith Kochmann (UCD GREP funded by IRCSET & IRCHSS)
 assess potential impacts on ecosystems
- Dannielle Green (SIMBIOSYS)

13. Spread of Pacific Oysters
• Worked with BIM, Marine Institute, Loughs
Agency and QUB
• Surveyed 69 intertidal sites with range of
characteristics
• Experimentally tested influence of macroalgae
and predators
• Genetically tested origins of wild
populations and whether self-sustaining

14. common
common
frequent
frequent
occasional
occasional
rare
rare
absent
absent

15. Spread of Pacific Oysters
• Establishment of wild populations limited at this stage
– a degree of control may still be possible
• Developed rigorous methodology for sampling and
identified factors associated with oyster establishment
• Found that crabs can eradicate post-recruits in some
areas and algae can slow growth, but effects variable
• Evidence for multiple recruitment events and decoupling
of establishing populations from local aquaculture
– need to manage establishing populations plus aquaculture
• Recommend triploid oysters to reduce reproduction
Kochmann et al in press Journal of Heredity
Kochmann et al in review Biological Invasions

16. Impacts of Pacific Oysters
• Experimental tests of potential impacts on biodiversity
and ecosystem functioning in a range of habitats and at
a range of densities

17. Impacts of Pacific Oysters
• Showed negative effects on protected habitat (Sabellaria
reefs) and changes to biodiversity (including apparent
facilitation of other introduced species)
– control of spread should be a high priority
• Dead oyster shells also
influential
• Effects varied with habitat
and density
Green et al. in revision
Marine Ecology Progress Series

18. Impacts of Pacific Oysters
• Oysters can alter nutrient cycling and
decomposition rates and potentially affect
primary productivity.
• Could affect ecosystem services, e.g. by
reducing carrying capacity for aquaculture.
OM loading N2 or N2O
Filtering
Phytoplankton
Biodeposits
Oxic Mineralisation Nitrification
sediment CO2 NH4+  NO-2  NO-3
Organic Matter
Anoxic CH4 Denitrification
sediment NO-3  NO-2  N2
Buried N and C

19. Work package 3
Assessing and reducing impacts of aquaculture
on marine biodiversity
4. Test potential impacts of introduced Pacific oysters
 Assess impacts of fish cages and test mitigation strategies
Dr Myriam Callier
 Provide management recommendations
Tasman Crowe, Myriam Callier,
Dannielle Green, Judith Kochmann,
Francis O’Beirn, Grainne O’Brien

20. Influence of salmon cages
• Tested extent of influence on benthic
communities using sampling and stable isotopes
• Assessed possible mitigation approach

21. Influence of salmon cages
• Low diversity under cages and high abundance
of opportunistic species
• Effects on communities extended 25-200 m
downstream, but <25 m perpendicular to flow
• Uptake of fish farm waste by benthic organisms
demonstrated + some evidence of dietary
switches
Callier et al. in revision Marine Ecology Progress Series

22. Influence of salmon cages
• Increased biomass of suspension feeders could
decrease levels of particulate and dissolved
material
• Potential mitigation strategy?
• Substrates for suspension feeders could be
deployed in sensitive environments, where a
small reduction in nutrients could be critical
Callier et al. in revision
Marine Ecology Progress Series

23. Approaches to reducing impacts
• Statutory programmes
• ECOPACT: Environmental Management
System for aquaculture
• CLAMS: Co-ordinated Local Aquaculture
Management Systems
• Mitigation measures include:
– Ongoing improvements in feeding efficiency
– Fallowing, rotation of cages,
reduction of culture densities
– Bioremediation, polyculture
– etc.

24. Future research needs
• influence on pelagic communities
• influence on ecosystem functioning & services
• spatial extent of influence and duration of
impacts - larger scales in space and time
• cumulative effects of separate farms
• synergistic effects with other stressors
• resistance and resilience of ecosystems
• carrying capacity of bays
• compatibility of aquaculture with conservation
objectives of SACs

25. Acknowledgements
HELP and ADVICE
• Ciarán McGonigle, Loughs Agency
• Grainne O’Brien & regional officers, BIM
• Catherine McManus & staff, Marine Harvest Ireland
• Heike Büttger, BioConsult, Germany
• Claire Guy & Dai Roberts, Queen’s University Belfast
FIELD and LAB WORK
• Jennifer Coughlan, Javier Atalah, Julien Chopelet, Kelly Dunagan, Paul Brooks, Jayne
Fitch, Erin Gleeson, Bas Boots, Angela Gallagher, Jesko Zimmermann
Rónan Mag Aoidh, Ciarán McGonigle & colleagues, Claire Guy, Francis O’Beirn
FUNDING AGENCIES and SIMBIOSYS coordination and management www.ucd.ie/marbee
• Environmental Protection Agency, NDP, SSTI, IRCSET & IRCHSS (via UCD Graduate
Research Education Programme in Sustainable Development), DEHLG
• Jane Stout, Jens Dauber and Dave Bourke, TCD