Jellyfish numbers aren't soaring

The University of Western Australia Science Alert 7 Jan 13;

Despite widespread belief that the world's jellyfish population is exploding, a new international study suggests that there is no real evidence of a global increase in jellyfish over the past two centuries.

The results of the study, "Recurrent Jellyfish Blooms are a Consequence of Global Oscillations", appear in the latest issue of Proceedings of the National Academy of Science.

The research was led by Dr Rob Condon of the Dauphin Island Sea Lab in Alabama, US with experts from the Global Jellyfish Group, a consortium of 30 researchers including lead co-author Winthrop Professor Carlos Duarte of The University of Western Australia's Oceans Institute.

The key finding of the study shows global jellyfish populations undergo concurrent oscillations with successive decadal periods of rise and fall, including a rising phase in the 1990s and early 2000s that has contributed to the current perception of a global increase in jellyfish. The previous period of high jellyfish numbers during the 1970s went unnoticed.

"There are major consequences for getting the answer correct for tourism, fisheries and management decisions as they relate to climate change and changing ocean environments," Professor Duarte said.

"The important aspect about our work is that we have provided the long-term baseline backed with all data available to science, which will enable scientists to build on and eventually repeat these analyses in a decade or two from now to determine whether there has been a real increase in jellyfish.

"The more we know, the better we can manage oceanic ecosystems or respond accurately to future effects of climate change," Professor Duarte said.