Artificial feed could be a game changer for tuna pens

The availability of artificial feed specifically designed for bluefin tuna could be a game changer in the sector.

Local tuna farmers are being encouraged to explore this new product with a view to eliminating or reducing the use of baitfish for feeding.

This emerges from an Environmental Impact Assessment (EIA) on the impact of tuna farms in the north of Malta. The study is related to a government proposal to change the current temporary status of the tuna pen holding zone into a permanent one.

“It would be advisable for the farm operator to be requested to provide a report on the viability of this feed,” the EIA carried out by ADI Associates states. It adds that changing tuna feeding practices from the traditional method of using whole fish could significantly reduce the amount of waste generated in the surrounding waters.

Artificial feeds are made from a combination of plant-based proteins, fishmeal, and other ingredients that provide the essential nutrients tuna need, thus reducing reliance on wild-caught species. The use of formulated feed would also improve water quality by limiting organic waste that currently results from excess fish parts, uneaten food, and the presence of scavenger species that congregate around the farms due to food remnants.

From temporary to permanent site

The EIA update assesses the environmental impact of making the temporary site permanent while retaining the approved total biomass of fish and all previously established conditions.

The current temporary site, which hosts tuna pens owned by AJD Tuna Ltd and Malta Mariculture Ltd, is located 4.7km from the protected Rdum tal-Madonna cliffs off Mellieħa.

The cliffs host large colonies of storm petrels, a sea bird. The tuna pen site is also located about 5km from Qawra Point in St Paul’s Bay.

This area is designated as a marine protected area.

A previous application submitted in 2019 had proposed locating the permanent aquaculture zone for northern tuna pens approximately 5.7km from the Mellieħa cliffs and 7.6km from Qawra Point.

However, the major drawback of the application was that the proposed site was only 4.6km away from Ħondoq ir-Rummien in Qala. The application was dropped following objections from the Qala local council.

Findings of the EIA update

The findings from the EIA confirm that the impact on seawater quality and the seabed from tuna farming operations has been minimal. The study monitored sedimentation levels and water parameters, concluding that while localised increases in organic matter were detected, they did not lead to significant long-term degradation. Existing mitigation measures, including the regulation of feed amounts and monitoring of waste dispersal, were deemed effective in maintaining overall water quality within acceptable limits.

However, uncertainty regarding the impact on bird populations remains. The report refers to the increased presence of seagulls and other scavenger birds that feed on discarded fish remains, raising the likelihood of seagulls preying on protected bird colonies. Reports of instances of seabirds becoming oiled with fish slime are also increasing. One of the recommendations made in the report is that a study be undertaken to assess the effects of the fish farms on seabird populations in the Maltese Islands, which should also examine predator-prey interactions.

Existing feeding practices

The report documents that current feeding and harvesting practices at the tuna farms follow established methods used in the industry. Bluefin tuna are fattened in offshore cages after being caught and transferred from the wild. Traditionally, they are fed with whole fish, such as sardines, herring, mackerel, and anchovies. It is estimated that it takes 10 to 25 kg of baitfish to produce 1 kg of tuna.

Harvesting takes place through a highly controlled process, ensuring compliance with international quotas and traceability regulations. Slaughtering is carried out by divers who enter the cage to shoot each tuna in the head.  The head, tails and guts of the tuna, being collected and transformed into protein-rich fish meal and Omega-3 and Omega-6 fish oils.

The report concludes that although surveillance and oil collection measures have been stepped up, the impacts from fish slime when this manages to escape the farm precincts and reaches the inshore areas, is still of major significance especially with regards to nuisance on other marine and coastal uses. Greater attention to this issue must be had, for as long as the tuna keep on being fed bait fish.