Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.

Vertical migration patterns of the jellyfish Pelagia noctiluca

VECTORS undertook a historical background review of the proliferations and the climatic, oceanographic and biological forcing for blooms of the most abundant stinging jellyfish in the Mediterranean Sea, the mauve stinger Pelagia noctiluca1. Over recent decades, man’s expanding influence on the oceans has begun to cause change in some regions, including in the Mediterranean Sea.


New proliferations of jellyfish may be occurring in the Mediterranean Sea, possibly in response to the cumulative effects of anthropogenic impacts.

Many of these “proliferation events” are due to P. noctiluca, an oceanic scyphozoan that has become very abundant along the coasts. Pelagia noctiluca is usually considered to be the most important jellyfish species in the Mediterranean Sea due to its widespread distribution, abundance, and ecological role and also because of its negative interaction with humans. Climatic conditions that favour enhanced reproduction by P. noctiluca and probably also determine optimal conditions for the formation of blooms are characterized by mild winters, low rainfall, high temperature, and high-atmospheric pressure.


Jellyfish occur in greatest concentrations along the northern Catalan coast and on beaches located close to marine canyons.

Data on beach strandings along the Spanish Catalan coast revealed that jellyfish occur in greatest concentrations along the northern Catalan coast and on beaches located close to marine canyons. The arrival of P. noctiluca at the coast depends firstly on the offshore production of jellyfish. Oceanographic structures like fronts, which enhance and maintain high levels of biological production and provide ideal conditions for feeding, growth, and reproduction of the jellyfish are present in the NW Mediterranean. The weakening of the front results in large numbers of P. noctiluca being driven into the coast by southeast winds. In the NW Mediterranean Sea, P. noctiluca exerts top-down control over a variety of prey including fish eggs and possibly the invasive ctenophore Mnemiopsis leidyi. Pelagia noctiluca is also responsible for the majority of the stings incurred by bathers along the Mediterranean coasts, with remarkable socio-economic impact on human activities in coastal areas.


Lead Author:

Stefano Piraino
Date of research: January 2015

Related articles:

Molecular recognition of moon jellyfish

Citizen science on jellyfish blooms

Genetic connectivity of Pelagia noctiluca populations

Growth model for jellyfish Pelagia noctiluca 

Invading seaweeds and resident assemblages

Jellyfish ecophysiology, ecology, biology and bioenergetics

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This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 266445
© Vectors 2015. Coordinated by Plymouth Marine Laboratory.