Researchers seek the best way to combat sea lice with minimum environmental harm

Akvaplan-niva has presented the POSITIV OPPDRIFT project which includes field investigations and theoretical modeling and examines whether liquid medicine pellets for combating sea lice cause lower environmental risks compared to the traditional method using the sinking feed.

Salmon farms in Norway have been using for over two decades the pesticide emamectin benzoate (EMB). This is an active ingredient contained in the lice products and it is usually administered via pellets to feed the fish.

As Akvaplan-niva explains, the unconsumed pellets with EMB remain on the seabed. The EMB will also affect marine sediments through fish feces and urine.

Other fish-producing areas like Scotland have already established stricter regulations for the use of EMB and its environmental consequences.

The POSITIV OPPDRIFT project conclusions

Researchers from Akvaplan-niva have seen a concentration of EMB in all sediment samples from both methods above the Scottish limit values.

However, concentrations of EMB in sediment samples taken near the floating pellet cages were up to 50% lower. Additionally, the amount of EMB was lower too in samples from the water column where liquid feed had been used.

Consequently, the project can prove that this method of drug administration with liquid feed can reduce the environmental risk of deworming.

Finally, the no-profit research institute alerts that more field trials should be done and that EMB concentrations in sediment samples taken 500 m from the facilities were "relatively" high.

The project Environmental Risk Assessment of a New Method for the Administration of Feed Drugs against Salmon Lice is led by Akvaplan-niva in collaboration with the Norwegian Institute for Water Research (NIVA), Skretting, and Salmo Pharma AS.