Drug-free treatment used in fight against sea lice
Marine Harvest Canada Inc. says it has successfully treated fish in a net-pen Atlantic salmon farm near Campbell River with a drug-free, chemical-free method for controlling sea lice.
A “hydrolicer” barge pulls fish from the pens into a tank where it uses pressurized water to dislodge sea lice, which are collected by filters for disposal, according to company spokesman Jeremy Dunn.
“Our veterinarians and operations people say the treatment went very well and so it is now part of our integrated pest-management system,” he said. “It’s the first time the hydrolicer has been used on the West Coast.”
B.C.’s fish farmers are keen to reduce their reliance on drug-based treatment, after DFO confirmed resistance to the feed-based treatment Slice in sea lice taken from Cermaq’s Bawden farm in Clayoquot Sound earlier this year.
The unit is most effective on fish through the middle of their growth cycle, said Dunn. “It doesn’t work on very big fish and it doesn’t work on very small fish.”
Having a drug- and chemical-free treatment option will help the company meet the requirements of the Aquaculture Stewardship Council, which certifies farms for environmental performance and sustainability, he said.
A recent report from SeaChoice noted that about half of B.C.’s ASC certified farms have difficulty meeting the certifier’s sea-lice thresholds.
Since 2009, salmon farmers such as Marine Harvest and Cermaq relied on the drug in Slice for sealice control. Since 2013, companies have been able to apply to Fisheries and Oceans Canada (DFO) to use hydrogen peroxide baths when Slice is ineffective.
“The hydrolicer is now the third tool we have and in January we expected to receive our freshwater well boat, which is our fourth tool,” said Dunn.
The 75-metre well boat draws fish into a tank equipped with a desalinator. Sea lice die after a few hours in fresh water.
“We can use that same vessel for (contained) peroxide treatments,” he said.
Cermaq will take delivery of its own $12-million, custom-built hydrolicer early in 2019.
“We need plan B, C and D, so we can mix up our approach and avoid being reliant on treatments that can lead to resistance,” said Linda Sams, sustainable development director for Cermaq Canada.
Cermaq Norway also began testing on a new semi-closed containment farm design in Norway late in September, said David Kiemele, managing director of Canadian operations.
The pens, made from a flexible composite, cost four to six times as much as traditional net pens and cost about 10 per cent more to operate, due to higher energy requirements.
The farm pumps water from a depth of 13 metres to prevent sealice infestations.
Cermaq is working with DFO and the provincial government to approve the design so it can begin trials here in Canada.
“If it reduces our treatment costs, it’s a business case we are prepared to make,” said Kiemele.
Resistance to Slice was documented by DFO in farms at Klemtu in 2013, in Esperanza Inlet in 2017 and again this year in Clayquot.
Lice from Klemtu showed a genetic signature for Slice resistance seen in other fish-farming regions, said DFO biologist Simon Jones, who specializes in parasites.
Marine Harvest reduced Slice applications and implemented hydrogen peroxide treatments at the Klemtu farms, which are operated in partnership with the Kitasoo/ Xai’xais First Nation.
Researchers found that two years after the initial outbreak, Slice resistance began to fade away, said Jones.