A pilot project trialling the use of manufactured feed for farmed tuna could be the solution to eliminating sea slime that pools on Malta’s coastline.
The slime that comes from fish farms is a result of the oils that leak from the baitfish used to feed the tuna.
However, the manufactured feed, which consists of a formulated diet tailored specifically for tuna, will not leak oil or nutrients into the sea and will prevent the creation of sea slime at the source.
The trial is being run on a small pen of around 150 Atlantic bluefin tuna off the coast of Marsaxlokk until the end of October. The fish will then be evaluated to see what effect the change in feeding method will have on the meat produced.
“We are trialling the use of manufactured food to see how it affects the fish, how it will affect their growth and whether it is good enough to be sold at foreign markets,” aquaculture expert Robert Vassallo Agius told Times of Malta.
“We’ve gone for manufactured food because it’s more sustainable and effective and will be good for the environment.
“Right now we use baitfish to feed the tuna and this results in a collection of oil that remains in the water and creates the inconvenience of slime,” Vassallo Agius continued.
“This new food and method of feeding will be able to eliminate the oil problem and it will successfully eliminate the slime.”
According to Sustainable Kinetics, the company manufacturing the formulated tuna feed, the product will not leak any oil or nutrients into the sea and will therefore do away with the problem of slime.
The feed, they said, is also more sustainable and cost-efficient. While it may be more expensive to purchase than bait fish, it is nutritionally dense and therefore less of it is required to adequately feed the tuna. It also supports better tuna performance and growth rate, which will make it three times more cost-efficient than using baitfish.
Since less feed is required, this will also result in fewer boat trips to transport it and simplifies the logistics of tuna feeding by lowering CO2 emissions as well as vessel wear and tear.
The product will not leak any oil or nutrients into the sea and will therefore do away with the problem of slime- Sustainable Kinetics
The manufactured feed also tackles the problem of the seasonality of baitfish which is variable, while manufactured feed will be available at a consistent quality on a year-round basis.
Sustainable Kinetics also said that the feed will extend the shelf-life of highly sought-after sashimi-grade tuna and intensifies the red colour of bluefin tuna meat.
Parliamentary Secretary for Fisheries and Aquaculture Alicia Bugeja Said said the move to manufactured feed for tuna farming would tackle the problem of slime at source.
“Thanks to this ongoing experiment, we are actively looking into having a proactive solution to the problem. Thanks to the alternative tuna feed, we are reducing the problem of lingering oil in the water.
“I hope it is successful so that we can continue to find more sustainable solutions to keep our seas clean so that people can keep enjoying them.”
Incidents of oily slime pooling in and befouling public bathing areas have been an issue that led to public outrage and complaints against the fish farming industry in recent years.
In 2016, a widespread slime incident had led to the suspension of fish farming permits after high-fat tuna feed was identified as the cause.
In 2018, a similar incident spurred fish farm operators to introduce a variety of mitigation measures which established common standards for feeding penned fish.
The measures included having a boom to collect oily residue and assigning a boat equipped with a skimmer to collect lingering waste material in the immediate area.
Fish farm operators were also able to sell the fish oil collected in the boons, which is used in some health products.