Sea lice control “breakthrough” for Scottish salmon farmers

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Two of Scotland’s leading salmon farmers have reported a major milestone in thein the rearing of cleaner-fish to tackle sea lice.

Marine Harvest Scotland and Scottish Sea Farms have been working with the Institute of Aquaculture at the University of Stirling to produce farm-reared ‘cleaner fish’, so-called because they eat naturally occurring external parasites such as sea lice from salmon.

Over six years, the project team has bred wild-caught Ballan wrasse (Labrus bergylta) and raised the offspring from egg to adults of reproductive age.

Now, in what is believed to be a world first, those same offspring have produced their own eggs, which have successfully hatched, completing the lifecycle of farming wrasse in a controlled environment.

Wrasse at sea cages, cleaning Atlantic salmon (article continues below)

The team has also gone on to successfully wean the wrasse larvae and fry from live food to a dry diet – another key milestone and one that will give salmon farmers more control over the health and nutrition of farmed wrasse.

Longer term, it’s hoped the breakthrough will help meet the growing demand for cleaner fish as Scotland’s salmon farmers increasingly seek to control sea lice through non-medicinal, environmentally-friendly approaches.

Currently, the majority of wrasse used as cleaner fish is wild-caught in accordance with guidelines specified by Marine Scotland, RSPCA Assured and local fishery boards to ensure it is done sustainably. However, it is the sector’s ambition to become self-sustaining and use only farmed stocks of cleaner fish – a goal that is now within grasp thanks to these latest advances.

Says Marine Harvest Scotland’s Hatchery Manager, Paul Featherstone: “Ballan wrasse provides highly effective, highly natural sea lice control and as such is in huge demand. With this breakthrough, we now have proven procedures for breeding, weaning and rearing wrasse, which will both help ensure farmers have a more secure, controllable supply and reduce reliance on wild stocks.”

Adds Scottish Sea Farms’ Head of Fish Health, Ralph Bickerdike: “These landmark breakthroughs are the result of many years of collaborative research, involving a significant investment of time and money by farmers and academic partners intent on developing natural solutions to the control of sea lice.”