Scientists’ use passenger ferry to tackle jellyfish ‘threat’

FERRIES crossing the Irish Sea are being used to police the arrival of jellyfish lethal to fish stocks.

In recent weeks scientists have begun using the passenger ferries on the busy shipping route as the first form of defence against the jellyfish.

This work involves co-operation between a research team in Swansea and University College Cork’s Dr Thomas Doyle, who has previously studied jellyfish patterns.

Dr Doyle said the latest development was proposed in response to November 21’s devastating fish kill in Northern Ireland when an army of Pelagia noctiluca stinger fish swept through a salmon farm.

“Scientists have ignored jellyfish because they are 96% water and were thought they had very little impact on the ecology.

“But we have seen in the Mediterranean they can cause havoc every year. Thousands of people are stung, they clog up fish nets or they can do worse like the serious fish kill we saw in Antrim,” he said.

The jellyfish arrived in Glenarm Bay in a shoal covering 16 square kilometres on the night of November 21. They were small enough to slip through the mesh surrounding the farm and killed 150,000 salmon.

To protect against future attacks Swansea University marine biologist Jon Houghton was given emergency funding from Britain’s Natural Environment Research Council to estimate the population in the Irish Sea.

He subsequently teamed up with Dr Doyle. The UCC division is funded through the Irish Research Council Science Engineering and Technology.

Dr Doyle said the unorthodox method of counting jellyfish from the decks of passenger ferries is effective.

“That is the method that works best to look at jellyfish. You can tell an awful lot just by throwing your head over the side of the boat and recording what can be seen.

“It is cost-effective and because there are routes right up the coast on both sides of the Irish Sea you get a good spread of information,” he said.

Dr Doyle said the amount of jellyfish in these waters has traditionally been underestimated but their impacts have gained more importance with the potential for further ecological upsets.

“In October, just prior to the fish kill I went out looking for jellyfish in the north-east Atlantic. There was an enormous amount of them, something nobody has been looking at.”