Giant frilly-mouthed jellyfish on the rise along British coastlines
Giant barrel jellyfish, recognizable by their large size and frilled texture, have been increasingly spotted off British coasts this year.
Jellyfish species have increased by 230 percent compared to last year, according to the Marine Conservation Society’s annual wildlife observation report.
Anna Bunney, citizen science program manager at the Marine Conservation Society, said: Times: “Volunteer reports show how dynamic and constantly changing our coastal ecosystems really are. The increase in barrel jellyfish sightings is particularly interesting.”
“While we need more records and data to help us understand these fluctuations, they may be linked to higher sea temperatures and changing ocean currents. That’s why our public observations are so vital: they help build a clearer picture of what’s happening in our seas and allow scientists to monitor changes in real time.”
Barrel jellyfish became the second most common species on the list, up from fifth last year.
Moon jellyfish, known for their translucent, rounded appearance, ranked first as the most commonly seen jellyfish species in the sea for the second year in a row.
A total of 316 jellyfish have been observed off British coasts this year; this accounts for 24 percent of the 1,327 jellyfish seen.
There has also been an increase in moon jellyfish blooms; This means an increase in population growth; 21 per cent had over 100 blooms, up 68 per cent on last year and the highest rate since 2016/17.
Mauve stinging flowers, also known as purple-striped jellyfish, also saw the highest increase ever recorded; a 31 percent increase over last year.
In Portugal, war cases have decreased this year, with 83 percent fewer reports. It was the second least seen species this year, compared to the second most seen species in 2024.
The Marine Conservation Society predicts this may be due to fewer storms this year (six compared to 12 last year) and fewer manfights being blown onto beaches by high winds.
More than half of the sightings occurred in the UK, and rankings varied geographically. Moon jellyfish were ranked highest in England, while barrel jellyfish were ranked first in both Wales and Scotland. Mauve needles were found largely along the south-west coast of England and Wales.
The report documented six per cent fewer jellyfish sightings in the UK and Ireland between 1 October 2024 and 30 September 2025 than last year.
