Two new jellyfish species reported for the Maltese islands

The seas around the Maltese Islands continue to stun and mesmerise marine biologists with new discoveries as two new jellyfish species have been recorded – the nomadic jellyfish (Rhopilema nomadica) – a painful stinger and an alien species – and the barrel jellyfish (Rhizostoma pulmo) – an innocuous and an indigenous species.

The barrel jellyfish report was submitted to the Spot the Jellyfish online reporting system by a member of the public last week, whilst the nomadic jellyfish was recorded on video by Calm Seas staff in 2004 at two different locations, but went undetected until the same video footage was recently reviewed by the Spot the Jellyfish team.

Both the nomadic and the barrel jellyfish are similar in appearance but they can be distinguished through a number of subtle differences, including a marginal blue ring around the bell, found only in the barrel jellyfish. Such reports bring the total number of new jellyfish species reported from Maltese coastal waters over the past year by the Spot the Jellyfish team to seven.

Both the barrel and the nomadic jellyfish are relatively large jellyfish species with a bell diameter hovering around 40-60cm but which can even reach the 90cm mark. The nomadic jellyfish species has an infamous reputation – in fact, since it entered the Mediterranean Sea via the Suez Canal in the late 1970s, it has appeared in biblical proportions in swarms along the coast of Israel and Lebanon ever since the late 1980’s.

Since then, like most other non-indigenous marine species entering the Mediterranean through the Suez Canal (the so-called Lessepsian migrants), it has spread west and in fact the nomadic jellyfish is also known from Turkey and Greece.

“Hence the confirmed reports of the jellyfish in Maltese waters mark the easternmost extent it has reached in the Mediterranean so far,” biologist Alan Deidun said. “The nomadic jellyfish has been implicated in some significant ecological and socio-economic impacts in the eastern Mediterranean, including the temporary shutting down of a coastal electrical powerstation in Israel in 2001 through the clogging of its colling water intake pipes.

“Fishermen in Israel, Lebanon and Turkey frequently discard whole netfuls of fish due to the preponderance of such a jellyfish amongst their catch, with other reports of this jellyfish even clogging and bursting fishing nets.”

Water temperature plays a crucial role in the reproduction of the nomadic jellyfish, with the medusa stage appearing once the water temperature exceeds 24 degrees Centigrade. For this reason, it was previously thought that the species would only limit itslef to the eastern Mediterranean, normally characterised by the warmest water temperatures, but the species now seems to have penetrated the Sicilian Channel.

Deidun stressed the fact that there was no cause for alarm, especially since the nomadic jellyfish species appears to be very rare in Maltese coastal waters, having been sited just two times since 2004. “Luckily, so far the nomadic jellyfish recorded in Maltese waters were individuals and not aggregations or swarms and the jellyfish is also easy to spot unlike other more cryptic ones. Bathers are urged to enjoy their bathing whilst keeping a vigil eye for such a species – if any other individual of this jellyfish is encountered, bathers are urged to contact the Spot the Jellyfish team on 23402843 or 79604109 or [email protected] to possibly arrange for the safe collection of such individuals from the bathing area.”