Picky indeed: perch, a cleaner fish for B.C. salmon

February 2, 2017 - Campbell River, B.C

Perch have the potential to become cleaner fish to remove sea lice from salmon farmed in British Columbia.

Local perch species have been shown to have a promising appetite for sea lice in 2016 trials carried out at the Department of Fisheries and Oceans, Centre for Aquaculture and Environmental Research facility in West Vancouver.

Marine Harvest Canada supplied juvenile Atlantic salmon while the Vancouver Aquarium provided four species of local perch: kelp, pile, striped and shiner perch, for initial trials, and then focused on the kelp and pile perch which appeared to have the best appetite for the lice.

Research leader Dr. Shannon Balfry is excited about the initial results and the potential application for the aquaculture industry.

“In our latest trial, we had 40 salmon infected with a total 370 adult lice, an average of nine per salmon. We introduced four little kelp perch who ate 364 lice in 11 days. We were feeding the perch chopped krill as well as feeding the salmon,” Dr. Balfry says.

From the very first days of trials, her team was confident that perch were as effective at cleaning as Atlantic species such as wrasse and lumpfish. They’ve taken video of the perch eating the lice, carried out post mortems to confirm sea lice present in bellies and counted exoskeletons in feces.

“They are quite shy and start by hiding in the kelp, but within hours of being held together in the lab tanks, the perch would immediately start to circle the salmon and check it out. We saw the salmon tilting to one side so the perch can better access the lice. We now have so much evidence that they are carrying out the role of cleaner fish.”

Dr. Balfry will continue the research at the BC Centre for Aquatic Health Sciences this year, with support from the BCSFA.

“The ability to use cleaner fish as biological controls to reduce sea life infestations in farmed Atlantic salmon would have such a widespread positive impact on the industry,” Dr. Balfry says.

“It would be an environmentally friendly solution, and an extremely valuable tool for B.C. salmon farmers to use to manage sea lice loads.”

This research is the first of its kind on the west coast. Perch were observed carrying out cleaner behaviour in the Pacific Ocean in the 1970s however research was not pursued until Marine Harvest Canada asked Dr. Balfry to find local alternatives for the cleaner fish used in Norway and Scotland.