Few reports of jellyfish so far this summer
But bloom could still happen later in the summer, expert says
The low number of mauve stinger jellyfish spotted in Maltese waters so far this summer could be down to meteorological factors or an increase in alien species that eat them, according to marine biologist Alan Deidun.
The mauve stinger (Pelagia noctiluca) is a small jellyfish that is recognisable by its purplish bell and trailing tentacles and known for its painful sting.
In recent years, the jellyfish have typically spawned in Maltese waters in the first two months of the year, before blooming around April and May. However, it has been conspicuously absent so far this year, much to the joy of swimmers.
“We haven’t received many reports of mauve stingers this summer, said Deidun, who runs the Spot the Jellyfish citizen science campaign.
The marine biologist speculated that the drop could be down to two possible reasons: meteorological factors, such as sea currents and a lack of northwesterly winds that would bring blooms closer to shore, and an increase in alien species that feed on the creatures.
However, fishermen had not reported a drop in the numbers of native fish species that feed on mauve stingers, such as the imperial blackfish (ħuta tal-bram), the Atlantic pomfret (pixxiluna) and the black ruff (lampuka tat-Torok), suggesting that the jellyfish could be present at lower depths.
Deidun did not rule out that a bloom could still appear later in summer, especially one that originated in the northern Mediterranean.
There is a lot we don’t know about the lifecycle of jellyfish, so it’s hard to predict when they will appear and in what numbers. No one year is like the previous one- Marine biologist Alan Deidun
“There is a lot we don’t know about the lifecycle of jellyfish, so it’s hard to predict when they will appear and in what numbers. No one year is like the previous one. Nowadays we’re used to seeing blooms every year, but up until the 1980s this would only happen every 12 years or so,” he said.
Since then, jellyfish numbers in the Mediterranean have exploded due to rising sea temperatures, increased pollution and nutrients such as sewage, aquaculture waste and fertiliser runoff, overfishing that removed competing species, and an increase in artifical structures.
“They’re a resilient species that can withstand heavy environmental stress,” he said.
Another species that had failed to appear so far this year was the by-the-wind sailor (Velella velella), which normally blooms between April and June.
The Spot the Jellyfish campaign is the oldest such initiative in Europe, having started in 2010.