The effect of ‘sea slime’ emanating from fish farms on aspects of the marine environment has not yet been thoroughly assessed due to a lack of studies, according to a new environmental report.
An Environmental Impact Assessment (EIA) on doubling the tuna cages at the Azzopardi Fisheries farm off Sikka l-Bajda states that on shore, the oily slick “is not envisaged to have any large adverse effects on marine species and habitats”, as it quickly biodegrades, but the EIA goes on to warn of a “lack of studies that deal specifically with this aspect”.
The report notes that the slime is “not deemed to have any toxic effects on pelagic [open sea] species and habitats” but that it is “aesthetically unpleasing and a nuisance to bathers, divers and coastal recreational activities”.
Moreover, a modelling exercise done as part of the assessment found that, once released from tuna farms, the slime could have a wide trajectory around the islands, even crossing the Malta-Gozo channel to the west coast.
There is a lack of studies on marine species, habitats
Oily residue formed from fats released from semi-frozen tuna feed hit coastal areas again last week, prompting fears of a repeat of problems that plagued local beaches two years ago.
Authorities blamed tuna farm operators, some of whom were found to have again violated their permit conditions, and ordered feeding to stop until the shortcomings were addressed.
Operators said on Saturday that they had introduced booms around their pens to collect the oily residue, having already signed an agreement last week on a variety of mitigation measures aimed at preventing a recurrence.
The booms, meant to collect much of the residue at source, will work with skimmer-equipped boats assigned to each pen. Operators will also set up a call centre to receive complaints from members of the public and will pay for two boats to patrol the coast and pick up marine litter.
The EIA report on the Azzopardi Fisheries extension also suggests a number of mitigation measures to eliminate or reduce residue.
These include carefully monitoring the feeding process and stopping as soon as, or just before, the fish are satiated. It also recommends regular checks – by an independent monitor – of the seabed below the tuna pens, which can suffer negative effects due to uneaten feed settling there.
Azzopardi has said its application to double the number of cages from 12 to 24 was necessary to give the tuna enough space to grow to optimal size. The plans will not involve any increase in the number of tuna held.
The relocation of the pens from Comino and St Paul’s Bay to the site around five kilometres off Sikka l-Bajda came after the Planning Authority revoked the farms’ operating permits amid public outrage over the slime outbreak in 2016.