2. Are the outbreaks of Pelagia noctiluca (Forsskål, 1775) more frequent in the Mediterranean basin? Mohamed Nejib Daly Yahia, Mirna Batistic, Davor Lucic, Maria Luz Fernández

In pelagic ecosystems, medusae are considered key predators, affecting zooplankton abundance and fish recruitment by preying on their larvae or competing for food (Purcell, 1997, 2003; Lynam et al., 2005). Thus, these gelatinous carnivores may be considered top predators as well as fish competitors (Purcell and Arai, 2001; Purcell, 2003). Several studies have demonstrated a significant increase in jellyfish abundance in different areas of the northern hemisphere, probably related to climate change and foodweb modifications (Brodeur et al., 1999; Mills, 2001; Lynam et al., 2004). Pelagia noctiluca is a holoplanktonic and oceanic, non‐selective, top predator that exercises top – down control in marine foodwebs and whose importance in the Mediterranean Sea became evident in the early 1980s during the so‐called “Pelagia years” (CIESM, 2001).

[1]  A. Brierley,et al.  Evidence for impacts by jellyfish on North Sea herring recruitment , 2005 .

[2]  S. Souissi,et al.  North Atlantic climate and northwestern Mediterranean plankton variability , 2005 .

[3]  S. Souissi,et al.  Phenological changes in the Northwestern Mediterranean copepods Centropages typicus and Temora stylifera linked to climate forcing , 2005, Oecologia.

[4]  Andrew S. Brierley,et al.  Interannual variability in abundance of North Sea jellyfish and links to the North Atlantic Oscillation , 2004 .

[5]  J. Purcell.  Predation on zooplankton by large jellyfish, Aurelia labiata, Cyanea capillata and Aequorea aequorea, in Prince William Sound, Alaska , 2003 .

[6]  P. C. Reid,et al.  Ocean climate anomalies and the ecology of the North Sea , 2002 .

[7]  P. C. Reid,et al.  Reorganization of North Atlantic Marine Copepod Biodiversity and Climate , 2002, Science.

[8]  Claudia E. Mills,et al.  Jellyfish blooms: are populations increasing globally in response to changing ocean conditions? , 2001, Hydrobiologia.

[9]  J. Purcell,et al.  Interactions of pelagic cnidarians and ctenophores with fish: a review , 2001, Hydrobiologia.

[10]  Steven R. Hare,et al.  Empirical evidence for North Pacific regime shifts in 1977 and 1989 , 2000 .

[11]  Claudia E. Mills,et al.  Evidence for a substantial increase in gelatinous zooplankton in the Bering Sea, with possible links to climate change , 1999 .

[12]  K. Nittis,et al.  Climatic changes in the Aegean Sea influence the eastern Mediterranean thermohaline circulation (1986–1997) , 1999 .

[13]  P. Morand,et al.  Long-term fluctuations of Pelagia noctiluca (Cnidaria, Scyphomedusa) in the western Mediterranean Sea. Prediction by climatic variables , 1989 .

[14]  J. Molinero.  Large contribution of the north Atlantic Ocean climate on the variability of plankton communities in the northwestern Mediterranean , 2008 .

[15]  C. Möllmann,et al.  Synchronous ecological regime shifts in the central Baltic and the North Sea in the late 1980s , 2005 .

[16]  J. Purcell.  Pelagic cnidarians and ctenophores as predators: Selective predation, feeding rates, and effects on prey populations , 1997 .