Sea lice linked to salinity not fish farms, study says
Sarah Douziech
The prevalence of sea lice on fish in Clayoquot Sound is more dependent on salinity levels than it is on proximity to fish farms, according to a new study released Monday.
The study is the result of a collaborative monitoring effort by the Clayoquot Sound Sea Lice Working Group made up of the Ahousaht and Tla-o-qui-aht First Nations, Creative Salmon Company Ltd., Mainstream Canada and coordinated by fisheries biologists with the Nuu-chah-nulth Tribal Council.
Since 2004, the Clayoquot Sound Sea Lice Working Group's objective has been to examine the prevalence and density of sea lice on wild fish found in 25 sites in Clayoquot Sound, including Bedwell Sound, Fortune Channel, Tofino Inlet, Herbert Inlet and Sydney Inlet.
The group found that the prevalence of infection of sea lice on Chum salmon fluctuated between seven per cent and 20 per cent between 2004 to 2007.
Numbers of species like Chinook, Coho, Sockeye, as well as Stickleback were too low in Clayoquot Sound to have any real statistical significance in the study, so the findings are only relevant to Chum salmon.
Biologist Katie Beach with Uu-a-th-luk (NTC fisheries) said the data showed there were no significant increases or decreases in sea lice numbers between 2004-2007, simply a fluctuation.
"Right now we can't say, for instance, that it's increasing or decreasing because so far we only analyzed the four years of data, and it's just showing an overall fluctuation," she said.
For example, the highest prevalence of sea lice was recorded at 20 per cent in 2006 and the lowest recorded prevalence was seven per cent in 2007.
The study also found that the fluctuation was dependent on how salty the water was and did not seem to be affected by water temperature.
Both salinity and temperature influence the life cycle of a sea louse, Beach explained, but in Clayoquot Sound, salinity plays a bigger role because it fluctuates more.
Water temperature in Clayoquot Sound did not vary significantly between test sites, but salinity did; the temperature was recorded as fluctuating between 10 to 14 degrees Celsius while the salinity ranged from five per cent up to 27 per cent.
The report noted that both the prevalence and abundance of sea lice infestation on Chum salmon showed a stepwise increase with increasing salinity.
Beach noted that salinity increases in years of lower precipitation. She said 2006, when the highest sea lice prevalence was recorded in Clayoquot Sound, was a really dry year.
The report noted that both the prevalence and abundance of sea lice infestation on Chum salmon showed a stepwise increase with increasing salinity.
Biologist Alexandra Morton, who has done years of sea lice research in the Broughton Archipelago and has led the fight against fish farms there, said though the study deserves applause for its collaborative nature, it doesn't reveal anything about sea lice that isn't already known.
"There are never any sea lice in freshwater, so numbers will always increase with salinity," Morton said. "It would be like saying breathing correlates with babies after they are born."
Morton said she was concerned that salmon farms are not mentioned in the body of the text of the report, or on the map showing the 25 sampling sites.
The exchange of sea lice between wild and farmed salmon has become a controversial topic in recent years in B.C. following a sea lice explosion in the Broughton in 2004 and research aimed at finding the cause.
"While sea lice numbers are indeed low, there is no reporting on how many fish, if any, were sampled near stocked fish farms," Morton said, adding that there is also no analysis of differences between numbers of lice near and distant to fish farms in the report.
Kevin Bruce of the Friends of Clayoquot Sound had similar concerns with the study, noting that no data from fish farms was included in it.
"Information from the fish farm companies was not used, like which farms were active at the time of the studies, the age of the fish in the active farms and if and when they were actively using toxic chemicals to reduce the sea lice on their fish," Bruce said. "Also missing are the sea lice levels of farmed fish."
Beach said some sampling sites in the study were located close to the fish farms and according to their summary, salinity seemed to play a more important role in determining sea lice numbers than proximity to fish farms.
And though the group didn't use any data from fish farms, Beach said that is something they hope to do in future study.
She said the study was meant to take a "snapshot" of the state of sea lice in the Sound and was not intended to address any questions about the impact of fish farms on sea lice numbers, or whether they are causing a problem or not.
"We don't have the same situation as the Broughton in 2004 when pretty much all the fish there were heavily infested with lice," Beach said, "and that's a relief."
However, Beach added that there is no baseline data from Clayoquot Sound, pre-fish farms, available to compare.
"We don't know what the natural level is," she said. "It is known that lice are a natural phenomenon, but how much of it is natural is not really known."
Beach also said there were many limitations to the study, including difficulty in doing regular site sampling, difficulty in comparing data because in the early stages they did not differentiate between fish species (2004-2006) and not tying their study with fish farm data.
The group hopes to also consider the different stages of sea lice development in their future examinations, Beach said, something Morton said would improve the validity of the findings as well.
Morton said she hopes fish farmers will not make any claims about the impact of sea lice on juvenile wild salmon based on this study because it doesn't address the question of whether fish farms are a contributor to its prevalence.
But Laurie Jensen, a spokesperson for Mainstream Canada, one of the collaborators in the study, said the findings of the study confirm what scientists in the Broughton have found.
"Salinity plays a larger role in sea lice than anything else," Jensen wrote in an email to the Westerly. "Proper management of farms can minimize any impact that they may have on the wild salmon."
Tim Rundle from Creative Salmon Company Ltd. in Tofino, also a collaborator in the study, said it is "interesting to know that salinity plays such a role to sea lice in Clayoquot Sound."
"We have two things going for us in terms of sea lice," Rundle said in an email. "One is that Chinook have a natural immunity to sea lice (Creative Salmon rears only Chinook salmon on their farms), and two, as our study shows, levels of sea lice are lower in areas of low salinity like Tofino Inlet where the majority of our farms are located."
Rundle said Creative Salmon has always had low levels of sea lice on their farmed fish and in their 20 years of operation in Clayoquot Sound, have never needed to treat for sea lice in any way.
Beach said edits to the report and the report itself had to be approved by all four partners in the study, the coordinator (Uu-a-th-luk) and the statistical consultant before it could be released.
"We worked as hard as we could to reduce the bias," Beach said, adding that there are always limitations to what they can look at because it is a partnership.
She explained that the group will continue its work and hope in the future to release a report again, perhaps under different parameters.
The B.C. Science and Innovation Council originally funded the study and later the Pacific Salmon Forum contributed. Every group involved contributed in-kind donations of people, time and equipment, going out once a week to count sea lice for the last six years.
Both Creative Salmon and Mainstream said they will continue to work closely with the monitoring group into the future in an effort to respect the concerns of the local First Nations and community.
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