Modelling transport and stranding of jellyfish Pelagia noctiluca in the Ligurian Sea

Abstract

Jellyfish bloom origins are generally sought in some biological response to the environment, leaving aside the role of transport patterns in redistributing existing populations. Here we use high resolution (1.25 km) ocean modelling to examine the role of transport in the onshore arrival and abundance of the pelagic stinging jellyfish Pelagia noctiluca on the Ligurian Sea coast. Jellyfish are modelled as Lagrangian particles with a 0-300m diel vertical migration typical of P. noctiluca. Over a year, onshore arrivals are not restricted to the summer period. Arrivals are concentrated at capes, but abundance can reach maxima in bays and in the lee of capes. Two factors impact jellyfish arrivals at the coast: the position of the Northern Current and the wind. A comparison of summer 2006 and available onshore jellyfish observations suggests a correct capture of the main stranding events by the model. These results have implications for understanding long term fluctuation