Raphael Vassallo Officials from the Ministry of Resources and Rural Affairs were this week dispatched to il-Kalanka, limits of Delimara, to investigate a slew of thick, white scummy pollution drifting into the bay from the direction of a nearby fish farm.
“Yes, the Fisheries Control Division started to investigate immediately as soon as notified and samples were taken,” a Ministry spokesman confirmed this week. “We are now awaiting laboratory results of the samples.”
The mysterious white scum, carried into the bay by the prevailing winds, has been a regular presence in il-Kalanka and surrounding coastal areas for the past few years.
Various theories have been brought forward to account for its recent appearance, including waste from the nearby power station, as well as discharge from merchant vessels which are permitted to bunker outside Marsaxlokk, and clean out their tanks before entering port.
However, regular frequenters of the bay – once a pristine and immensely popular bathing spot – are convinced that the substance originates from the nearby bluefin tuna farm, less than one kilometre to the northwest: a view shared by many in the diving community.
Shawn Arrigo, an experienced diver and underwater photographer, suspects this to be excess fat and oil from bait used to feed fish in fish farms, as similar pollution has been noted underwater in all areas where there is a concentration of fish farms in the vicinity.
Stills from Arrigo’s underwater footage, reproduced here, show the dramatic effect of this oily pollution on the underlying meadows of Poseidonia: a protected species of seaweed essential to the Mediterranean marine ecosystem.
As the photos show, the film of oily fat coats the Poseidonia, producing a cobweb-like effect which ultimately stifles and kills the plant.
As for the floating white scum, this is believed to emanate from tuna ranches in particular: not just in il-Kalanka, but in other areas where such facilities exist, including St Paul’s Bay and the Qawra coast.
Industry expert Robert Mielgo Bregazzi, of Advanced Tuna Ranching Technologies, explains that such milky-white scum is an inevitable by-product of the tuna ranching industry itself.
“Bluefin tuna naturally produces its own fat, which it releases into the sea as it swims,” Bregazzi said, adding that this natural fat would normally be absorbed by the sea without leaving any discernable trace. But when tuna are concentrated in large numbers and confined within a small space, the excess fat tends to coagulate and float in the form of a thick film of white scum.
Bregazzi explains that this also mixes with the fatty residue of the enormous quantity of bait – mainly mackerel and squid – required to fatten the tuna before it is slaughtered and sold on the international market, mostly to Japan.
As with other fish farms, excess food sinks to the bottom, spreading pollution over a substantial area across the seabed.
“To increase the weight of one kilo of bluefin tuna by 12% during a four- to six-month fattening season, 4 to 4.5 kilos of bait would be needed,” Bregazzi told MaltaToday, “So if you input 10,000 tonnes of live tuna into cages, you will need to feed them 40,000 to 45,000 tonnes of bait during a four- to six-month fattening season for each specimen to increase its weight by 12% prior to being slaughtered.”
The precise tonnage of live tuna currently held in Malta’s pens remains a jealously guarded secret, as the MRRA has to date refused to divulge the information despite numerous requests by this newspaper.
However, the total capacity of Malta’s tuna farms amounts to 12,300 tonnes, of which one 1,000-tonne facility is currently inoperative. If the remaining farms are filled to 75% capacity (a conservative estimate by all accounts), Malta’s tuna ranches would require a minimum total of over 33,900 tonnes of fish-food/bait per year.
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