A new Simon Fraser University-related study confirms sea lice from salmon farms are compromising wild fish populations.
It is based on the most comprehensive examination of sea lice from salmon farms and wild salmon dynamics in British Columbia to date.
“I don’t know if I would go so far as to call our study seminal,” says SFU researcher Brendan Connors, a postdoctoral fellow in SFU’s School of Resource and Environmental Management.
“But it shows that once you consider all the available information, there is support for a negative relationship between lice on farms and the productivity of adjacent pink and coho salmon populations. Contrary to the previous study (known as Marty et al. 2010), we conclude B.C. economies and ecosystems that depend on wild salmon would benefit from management and policy designed to minimize louse transmission from farmed to wild salmon.”
Larry Dill, SFU biology professor emeritus, who supervised Connors doctoral thesis at SFU and independent biologist Alexandra Morton, an SFU honorary degree recipient, are among the new study’s six co-authors.
Connors and Dill were scheduled to appear before the Cohen Commission of Inquiry into the Decline of Sockeye Salmon in the Fraser River Aug. 25, 26 and 29.
The study, “Effects of parasites from salmon farms on productivity of wild salmon,” has just been published in the August 22, online issue of the Proceedings of the National Academy of Sciences.
“For pink salmon, estimated mortality ranged from 88 per cent when lice were abundant down to one per cent when lice were less abundant. For coho salmon, estimated mortality reached 92 per cent when sea lice were abundant and was as low as two per cent when lice were rare.”
The researchers went beyond reviewing previous studies that have reached contradictory conclusions about the impact of sea lice from fish farms on nearby wild salmon.
They reanalyzed data collected for a study known as Marty et al. 2010, the first with access to data on the number of sea lice on farmed salmon. It found no relationship between the productivity of pink salmon and the number of sea lice on farmed salmon in the year the pinks went to sea.
The authors concluded that management actions and policies that separate wild and farmed salmon would not benefit the productivity of wild salmon.
This new study used the same sea louse data as the Marty et al. 2010 study. It looked at pink as well as coho salmon before the emergence of salmon acquaculture. The 2010 study only looked at pink after the emergence of salmon farming.
Also beyond the 2010 study, this study looked at adjacent pink and coho populations not exposed to salmon farms.
When all the information is considered, the authors of this new study come to the opposite conclusion of Marty et al. 2010.
“Our approach is more thorough and telling (i.e., it allows us to better estimate the effect of sea lice) because it allowed us to incorporate information from pink and coho populations both during and before exposure to sea lice from salmon farms as well from adjacent populations that are not exposed to salmon farms. The Marty et al. 2010 paper only consider pink salmon populations during exposure to lice,” Connors said.
“The existing management and policy measures designed to protect wild juvenile salmon from sea lice from salmon farms include moratoriums on the expansion of salmon aquaculture; fallowing (emptying) of salmon farms along juvenile salmon migration routes; parasiticide administered to farmed salmon in their feed; and placement of salmon farms in closed systems on land,” he said.
“There is currently a moratorium on the expansion of salmon aquaculture north of Cape Caution in B.C. (just north of the north end of Vancouver Island) and there is a coordinated management plan in the Broughton Archipelago that combines fallowing and parasiticide use to control louse exposure to wild juvenile salmon.”