A representative for the Federation of Maltese Aquaculture Producers could not guarantee a slimeless summer, despite booms being installed and fish farm operators agreeing to self-regulatory measures.

Summers over the years have been plagued with sea slime appearing along the coasts of areas such as Marsascala and Sliema.

This year’s slime had caused concern since it coincided with the start of the tuna feeding season. In 2016, tuna farms around the island were identified as the source of the widespread incidence of a similar, oily slime.

Federation secretary John Refalo, when pressed at to whether new mitigation measures could guarantee that slime would not crop up on shores said: "Our guarantee is that we will keep doing what we are doing and include better systems to minimise and reduce the waste of our product."

"Incidents will happen no matter what you do," Mr Refalo added.

A man pushes slime in tuna cages towards a skimmer, a device that removes oil. Photo: Jonathan Borg

The re-emergence of slime prompted a swift response from the fish farm operator lobby this year.

A visit to the site shows workers, as early as half past six in the morning, using a squeegee to push the slime in fish pens towards what is known as a "skimmer" - a device that collects and removes oil from the surface of the water.

Booms were installed to collect oily residues and a skimmer-equipped boat to each pen was assigned. Half the one-metre high boom is underwater.

Fish farms are also refraining from feeding fish during stormy weather, for fear that the slime generated almost instantaneously after feeding makes its way beyond the cage because of rough winds or currents.

"We are building up our capacities to ensure that even if we do have an incident, we can intervene immediately," Mr Refalo said. However,he admitted the mitigation measures were a learning process and more could be done to minimise and reduce waste.

Operators had also set up a call centre to receive complaints from members of the public and would be paying for two boats to patrol the coast and pick up marine litter wherever they found it, the Federation of Maltese Aquaculture Producers had said.