New study says sea lice greater problem to wild
salmon than once thought
JEREMY HAINSWORTH
VANCOUVER (CP) - The spread of parasitic
sea lice from farmed salmon to wild populations may be more
extensive than previously believed, says a report published
Wednesday in a British scientific journal.
"Our research shows the impact of a single
farm is far-reaching," Marty Krkosek, the lead author of the
report, said in a news release. Krkosek, a researcher at the
University of Alberta's department of biological sciences,
said sea lice incidence near a farm studied by the research
team in April and May 2003 in the Broughton Archipelago off
the coast of British Columbia was 30,000 times higher than
natural.
"These lice then spread out around the
farm," he said. "Infection of wild juvenile salmon was 73
times higher than ambient levels near the farm and exceeded
ambient levels for 30 kilometres of the wild migration
route."
The report also says the impact of the lice
could move through entire coastal ecosystems, affecting
populations as diverse as herring, whales and seabirds.
The report was published in the Proceedings
of the Royal Society, a publication of Britain's national
academy of science.
It cautions that it may be time to
reconsider industrial fish farms in wild habitats.
"There's a double bottom line here," said
John Volpe, a marine ecologist at the University of Victoria
and one of three scientists who wrote the report.
"The full ecological costs of
industrial-scale salmon farming must be quantified as well as
the economic ones."
But Mary Ellen Walling of the B.C. Salmon
Farmers Association said more studies are being done and once
those are complete the industry would have a greater
understanding of the impact of salmon farming on the B.C.
coast.
"We're continuing to work with the
scientific community," Walling said. "Every piece of
information contributes to the overall body of knowledge.
"There's a lot of work that needs to
continue and I think that's what this study points out more
than anything else."
The report comes a week after the
Department of Fisheries and Oceans conceded fish farms in the
Broughton Archipelago opposite northern Vancouver Island are
the "probable" source of a huge increase of sea lice found on
wild salmon in 2004.
At a briefing last week, Fisheries
Department scientist Brian Riddell said it may take three to
five years to reach a definitive conclusion about the effect
of sea lice from fish farms on wild salmon mortality,
however.
While final results of last year's sea-lice
sampling won't be released until mid-April, the Fisheries
Department reported an increased prevalence of sea lice -
especially a salmon-specific species - on young wild salmon
compared with the previous year.
Chum salmon appeared harder hit than pinks,
with an infection rate of 25 per cent.
However, the department said, there was no
evidence that carrying the parasite affected the physical
condition of the infected fish, which points away from sea
lice as a cause of increased mortality.
The federal department's research program
for 2005 includes laboratory studies in Nanaimo, B.C., Halifax
and Washington state to gauge the effects of sea-lice
infestation on salmon health and growth.
It also includes an expanded sampling
period in the Broughton Archipelago and closer assessment of
lice numbers on both wild and farm salmon stocks.
Fish farm operators have been dosing their
pens with a controversial drug called Slice, which critics say
poses potential health and environmental risks.
The report published Wednesday studied
infection levels in migrating juvenile pink and chum salmon as
they moved seaward along a B.C. coastal fjord past two farms.
They took data from 5,500 fish, taking measurements every two
to four kilometres.
They say the fish carried almost no sea
lice prior to being near the farms but became heavily infected
as they approached.
The parasites create lesions on the surface
of fish, compromising their ability to maintain their
sea-water balances, a situation the researchers say can be
fatal.
Ordinarily, the report says, juvenile pink
and chum do not have to contend with sea lice as adult fish
are out at sea and widely dispersed.
By the time migrating stocks normally
encounter lice, they have had time to put on body mass and
build resistance to the
parasites.
