High ocean temperatures and poor timing of parasite management likely led to an epidemic of sea lice in 2015 throughout salmon farms in British Columbia's Queen Charlotte Strait, a University of Toronto-led study has found.
The sea lice spread to migrating juvenile wild salmon, resulting in the highest numbers of sea lice observed on wild salmon in a decade.
In spring of 2015, a team of U of T ecologists led by postdoctoral researchers Andrew Bateman and Stephanie Peacock found that more than 70 per cent of fish the team sampled in the Strait's Broughton Archipelago had at least one sea louse: the highest prevalence of such parasites since 2005.
"It was sort of a perfect storm of environmental conditions and mismanagement of treatment," says Peacock, a postdoctoral fellow in the U of T's Department of Ecology & Evolutionary Biology when the research was conducted. "A lot of people talk about how sea lice are natural, but in farms, you have these parasites in larger numbers. Juvenile wild salmon are then exposed as they migrate past these areas."
High ocean temperatures and poor timing of parasite management likely led to an epidemic of sea lice in 2015 throughout salmon farms in British Columbia's Queen Charlotte Strait, a University of Toronto-led study has found.
The sea lice spread to migrating juvenile wild salmon, resulting in the highest numbers of sea lice observed on wild salmon in a decade.
In spring of 2015, a team of U of T ecologists led by postdoctoral researchers Andrew Bateman and Stephanie Peacock found that more than 70 per cent of fish the team sampled in the Strait's Broughton Archipelago had at least one sea louse: the highest prevalence of such parasites since 2005.
"It was sort of a perfect storm of environmental conditions and mismanagement of treatment," says Peacock, a postdoctoral fellow in the U of T's Department of Ecology & Evolutionary Biology when the research was conducted. "A lot of people talk about how sea lice are natural, but in farms, you have these parasites in larger numbers. Juvenile wild salmon are then exposed as they migrate past these areas."
Because farmed salmon are in open net pens and share water with nearby wild salmon, the parasites can transmit to young wild salmon who wouldn't normally encounter sea lice until later in life. These young fish are sometimes as small as three centimetres in length, while sea lice themselves can be close to one centimetre in diameter.
"Getting sea lice at such an early age affects young salmons' health and their ability to fend off predators," says Peacock.
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Image: Salmon via Aaron Dufault / http://wdfw.wa.gov/
