Wrasse welfare

Lumpfish (Cyclopteridae) and wrasse (Labridae) are natural predators for sea lice, and picking lice off from larger fish like salmon is natural behaviour for these species. Keeping cleaner fish in pens with salmon has been shown to help keep lice numbers down in a way that has minimal impact on both the salmon and the environment.

There are signs, however, that some fish farmers are rethinking their strategy with cleaner fish, for several reasons – particularly because there is now greater awareness of cleaner fish welfare issues.

Last May, a revised edition of the RSPCA welfare standards for farmed Atlantic salmon came into effect. While not statutory, this matters, because most of the UK’s salmon production comes under RSPCA Assured’s welfare scheme. The new edition includes more specific requirements for cleaner fish, in particular demanding that they must be safely separated from the salmon in the pen before treatment or transportation takes place.

Meanwhile, farmers now provide cleaner fish with appropriate feed sources – they cannot survive on sea lice alone, and they prefer to graze on feed blocks rather than compete with the salmon for pellets – and artificial hides to replicate the seaweed beds in which they like to take shelter. All this helps to reduce stress for the cleaner fish and allow them to do their job.

In Scotland, the use of lumpfish has been largely discontinued – while these fish are effective cleaners, they have proven to be problematic when the salmon are being treated or transported. Lumpfish like to attach themselves to flat surfaces and this can cause problems when fish are being pumped to another location such as a wellboat.

For wrasse, the picture is more mixed. A spokesperson for Mowi said: “Mowi continues to use wrasse as part of its sea lice treatment programme, sourced from Mowi’s hatchery in Anglesey as well as some wild stocks.”

Mowi-owned Wester Ross also uses wrasse as cleaner fish, and Bakkafrost and Scottish Sea Farms use wild-caught (but not farmed) wrasse.

In contrast, Cooke Scotland said: “Cooke Scotland does not use cleaner fish in its salmon farming operations. We continually develop and assess the best methods of sea lice control on our sites to ensure our salmon are cared for to the highest welfare standards.”

Concern over the sustainability of the wild wrasse fishery has led to increasingly tight controls. The Scottish Government and Salmon Scotland initially introduced voluntary controls in 2018. These were later made mandatory in 2021 through a licence condition, requiring a Letter of Derogation for those wishing to commercially fish for wrasse.

Wrasse fishers are limited to a maximum of 250 creels and there is a closed season for wrasse fishing in some areas, typically between April and mid-July. In addition, some areas have been designated as “no take” zones to protect stocks.

Up until recently, Otter Ferry Seafish maintained a wrasse farming operation to supply adult wrasse to the Scottish salmon industry. This has now been wound down and the company now maintains broodstock only, to supply larvae to a producer in Norway, where there is still a greater demand for cleaner fish.

It takes two years to grow wrasse to adult size, so investing in future production represents a commercial risk if the market is uncertain. Even so, Otter Ferry’s Managing Director, Alastair Barge, stresses that cleaner fish continue to play a role in protecting salmon: “It’s still a tool in the toolbox.”