Swarms of jellyfish are increasingly being reported from seas around the world. These swarms, or blooms, can cause changes in food webs and have detrimental effects on fishing, tourism, industry and local economies.
Jellyfish blooms, or “smacks”, have recently been reported off the coasts of Devon and Cornwall and are a regular occurrence in several Mediterranean countries. Many blooms are formed by non-stinging jellyfish and are quite safe but the UK Foreign Office has warned travellers to heed local advice about jellyfish. The cause of these blooms can vary from place to place but a significant factor is the warming of ocean waters, which is enabling warm water species to invade new areas. When this is coupled with the construction of artificial reefs or flood defences, hard substrates which are preferred sites for the larval stages of jellyfish, it can create ideal conditions for jellyfish populations to surge.
Part of a EU funded research project, VECTORS, coordinated by the PML, is working to understand and manage the impact of jellyfish blooms on the tourist industry. In a survey of beach-goers in Catalonia, Spain, it was found that people were prepared to extend their journey times by a third to travel to a beach with less risk of jellyfish outbreaks. When this data is combined with the respondents’ travel costs it gives a total cost of approximately 300 million Euro per year.
Mel Austen, VECTORS Coordinator said: “VECTORS is investigating changes in our European seas with a focus on invasive species and fisheries with the aim of informing future policy and management of our seas and providing advice and information to the public.”
To help people identify which beaches are at greatest risk from jellyfish outbreaks VECTORS scientists have also produced an iPhone and android app which gives daily updated information on jellyfish at beaches in the Barcelona area. The app includes details on how to identify jellyfish, how to treat jellyfish stings and it also enables users to report new sightings and ask questions of jellyfish experts.
Fisheries can also be seriously affected by jellyfish. Trawling and purse-seine fishing can be disrupted by net clogging and the inability to sort catches, whereas overfishing of an area can reduce the number of competitors leaving more food for jellyfish. A recent report from the UN Food and Agriculture Organization concluded that this was creating a “vicious circle” as the jellyfish are also feeding on the eggs and larval stages of fish, further reducing the fish population.
Industry can also be affected by blooms of jellyfish and there have been several cases of coastal power stations being closed to prevent cooling water systems being clogged by the animals.
However, it’s not all bad news about jellyfish. The animals are a rich source of antioxidants and the Chinese have been eating them for millennia. A VECTORS study has found that an extract from the fried egg jellyfish (Cotylorhiza tuberculata) has significant anti-cancer properties.
Stefano Piraino, a scientist working on the VECTORS project said: “There is documented evidence that non-stinging jellyfish in the Mediterranean can be eaten. They are full of antioxidants and molecules which can be used in the pharmaceutical and cosmetic industries. We should learn to love jellyfish and view them as a resource and not a pest”.