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Resistant pests
"What happened there was very undesirable, both from our point of view and from that of the company," said Zachary Waddington, chief veterinarian of aquaculture for DFO in the Pacific region. "It was a bit of a perfect storm."
The company has been diligent in identifying the type of sea lice present on the affected farms and has responded by using conventional drug treatment approved for use in British Columbia. called SLICE, says Waddington.
But when the number of lice began to increase and remain stubbornly high, it was obvious that the parasites had become resistant.
Resistance to treatment is a phenomenon known worldwide in the world of aquaculture, but is a relatively rare experiment in fish farms in British Columbia. There have only been two other documented cases in recent years.
Environmental factors also come into play at Clayoquot Sound. The heavy rains that usually hit the west coast of Vancouver Island in the winter did not come with the same revenge as usual.
As a result, ocean salinity has remained high, creating favorable conditions for sea lice proliferation, Waddington said.
Zachary Waddington is DFO's Senior Aquaculture Veterinarian in the Pacific Region. (Megan Thomas / CBC)
Zachary Waddington is DFO's Senior Aquaculture Veterinarian in the Pacific Region. (Megan Thomas / CBC)
It was clear that another option was needed to fight pests and the company asked the province for permission to use a hydrogen peroxide treatment.
But in the nearby town of Tofino, opposition to a chemical in the ocean has aroused strong opposition, and the permit has been delayed, he said.
"What happened in the end was largely unprecedented – not necessarily the problems of resistance, but the scale at which it happened in Clayoquot was unprecedented."
The epidemic raged as the wildest vulnerable wild juvenile salmon left the rivers and entered the ocean to begin their migration.
Sea lice generally do not harm adult fish, but young fish may have adverse effects when parasites attach to the skin.
"So, basically, from the beginning of March, that is, from the beginning of emigration, until June, lice levels were more or less mismanaged, because they did not have any tools, "says Waddington.
Waddington explains why sea lice on fish farms is a concern in this video:
Clayoquot Sound is located on the west coast of Vancouver Island.
Clayoquot Sound is located on the west coast of Vancouver Island.
Opponents of net open-net fisheries consider drug-resistant sea lice as a new, riskier border that may impact wild salmon in British Columbia.
"Once you have drug resistance, you're in a whole new sea lice management regime," said Karen Wristen, executive director of the Living Oceans Society.
"The worldwide experience suggests that controlling them is beyond the capabilities of salmon farms."
Wristen has published a report with anti-fishing activist Alex Morton of the Raincoast Research Society. Mousy Choices gives a detailed overview of what happened in Clayoquot Sound and whether the industry and DFO should have been better prepared.
He also outlined concerns about juvenile wild salmon, noting that many of the wild fish sampled in the region this year were infested with sea lice.
DFO officials confirm the wild salmon sampling data. But Waddington says the impact of the infestations remains to be seen.
"There is far from a scientific consensus on the level of sea lice, and possibly where appropriate, that could harm the wild salmon population," Waddington said.
As for resistance to treatment, he says that it is a concern, but that we do not expect it to generalize to the BC. fish farms.
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