Maltese bays are being cluttered with “zillions” of jellyfish thanks to the “anomalously” calm and warm December that has advanced spawning this year.

Although the early timings for the egg laying could indicate a jellyfish-free summer, marine biologist Alan Deidun said it was too early for predictions given the variability of the marine environment.

But a “massive” mauve stinger bloom, consisting of the next generation of jellyfish, can be expected sometime in early spring – late March – as long as February and March are not exceptionally cold and stormy, he could safely say.

“How many of these juvenile jellyfish appearing in spring survive will then determine how many jellyfish we will actually observe in summer,” Deidun continued.

Over the past few weeks, reports of adult mauve stingers by numerous citizen scientists have flooded into the ‘Spot the Jellyfish’ campaign, coordinated by Deidun.

Their resurfacing took place a tad earlier than usual, as the egg laying generally occurs over the January-February period, he said.

“This means the next generation of jellyfish medusae hatching from the laid eggs will come of age over the next two to three months, as long as the water temperature does not plummet considerably as happened last year, arresting their development,” Deidun explained.

The mauve stinger is the most common jellyfish species in the Mediterranean and in the north-east Atlantic.

The calm conditions over the holiday season in what is normally the wettest month of the year also meant the jellyfish eggs and the emerging larvae would not be dispersed far away from the bays where they were released.

The mauve stinger is the most common jellyfish species in the Mediterranean and in the north-east Atlantic.

Up till the 1980s, blooms used to occur on average once every 12 years while, in recent years, these have become an annual occurrence, Deidun explained.

During autumn, with the arrival of the first storms, adults of the species descend to the deep sea, even reaching depths exceeding 1,000m, only to resurface in early winter to release eggs before dying en masse, he continued.

The exact timing of the resurfacing event varies each year and depends on a number of complex factors, most notably sea conditions, such as water temperature and the degree of storminess.