Coastal Economies Can Feel The Sting Of Jellyfish

Photo  of  diver measuring a giant barrel jellyfish. Copyright Thomas BastianThe serious impact of jellyfish swarms on coastal economies was described by Dr Tom Doyle of the Coastal & Marine Resources Centre at University College, Cork at a recent Beaufort Marine Socio-Economic Workshop at the Marine Institute,

Once considered unimportant as a factor in coastal economies, jellyfish are now playing increasingly significant roles in coastal ecosystems and processes. This has happened due to regular occurrence of jellyfish blooms around the coast of Ireland with negative consequences for tourism, fishing,  and fish farming.  

“In 2005 people were simply afraid to get into the water around Dublin because of blooms of the dangerous ‘Lion’s Mane’ jellyfish,” said Dr Doyle. “And the emergence of ‘open water swimming’ as part of triathlons means that more and more swimmers can potentially come into contact with these animals.”  

But jellyfish are not only a threat to swimmers. Large swarms of jellyfish were responsible for the destruction of an entire fish farm’s stock of salmon, worth £1 million, in Glenarm, Northern Ireland in 2007.  

Photo of Aurelia jellyfish bloom copyright Michelle Cronin

Swarm of jellyfishFishermen too are noticing the problem as their nets become clogged with masses and masses of jellyfish on an increasingly regular basis. “Not only do the jellyfish clog the nets and make them less efficient, but the increased cost of labour in removing them, not to mention the danger of capsize as smaller boats attempt to pull in their bulging nets, or the painful stings encountered in removing them, are making jellyfish a serious threat to fishing during times when they occur,” said Dr Doyle. “I know of one example when the sheer weight of jellyfish in a pair-trawl off Dublin was large enough to physically stop the boats pulling it in their tracks.”  

Dr. Doyle suggests that increasing seawater temperatures related to climate change, increased eutrophication in coastal waters and overfishing may have contributed to their increase in recent years. “As we continue to remove enormous amounts of fish from the sea, we can open up ‘ecological space’ for jellyfish to fill, as the removal of such fish provides more food (zooplankton) for jellyfish” he said.  

Dr Doyle is currently involved in an EU project ECOJEL project, to track the migration of jellyfish in European waters and better understand their movements and overall ecology as well as the Marine Institute NDP-funded project GILPAT that is examining the effect of jellyfish on farmed salmon.  

Further information on these projects is available at  

The workshop, which was held at the Marine Institute headquarters at Oranmore, Co. Galway was organised by NUI Galway to discuss the results to date from work carried out by its newly formed Socio-Economic Marine Research Unit (SEMU) and research being carried out nationally in the area of marine socio-economic research.    

For further information, please contact:  

Dr. Tom Doyle – Coastal and Marine Resources Centre.

Phone: 021 4703119      Email:  Or  

Dr. John Joyce – Communications Manager, Marine Institute

Phone: 087 2250871    Email:  



The EcoJel Project is a four year project funded by the European Union Regional Development Fund (ERDF) under the Ireland Wales Programme 2007-2013 – Interreg 4A. EcoJel is a collaboration between Swansea University (Wales) and University College Cork (Ireland). EcoJel aims to assess the opportunities and detrimental impacts of jellyfish in the Irish Sea. The strategic objective of EcoJel is to identify and manage the jellyfish threats and opportunities in the Irish Sea. The specific aims are to:  

1) Identify the threats of jellyfish nuisance blooms to bathers and to raise the awareness of jellyfish so that impacts are minimised (Jellyfish Action and Awareness Campaign)

2) Establish the movements and origin of pest jellyfish through the development of innovative tracking technologies (JellyTag)

3) Identify the impacts of jellyfish on fisheries and aquaculture and develop models to explore outcomes of climate change (Jellyfish and Ecosystem Services)

4) Identify the economic potential of harvesting jellyfish in a sustainable manner and a potential eco-tourism industry for recreational divers (Jellyfish Potential)

5) To build on the successful INTERREG IIIA Irish Sea Leatherback Turtle Project and consolidate the collaboration between the University College Cork and Swansea University by establishing the Irish Sea as a ‘centre of excellence’ for jellyfish research (JellyCore)   

The GilPat Project consists of a consortium of the CMRC, the Marine Institute (lead partner), Vet-Aqua International, the Agri-Food and Biosciences Institute (Belfast), and the Irish Salmon Growers Association. GilPat will investigate gill pathologies in salmon farms and has the objective of identifying causative agents.

The CMRC’s role is to investigate the abundance and identity of jellyfish found at or near salmon farms over the course of the study. Jellyfish are known to cause gill pathologies so it is important to gather information of which species occurs and how abundant they are in order to develop early warning systems and technologies for mitigating there affect.  

This project (Grant-Aid Agreement No. PBA/AF/08/002(01)) is carried out under the Sea Change strategy with the support of the Marine Institute and the Marine Research Sub programme of the National Development Plan 2007–2013, co-financed under the European Regional Development Fund.