The demand for salmon has certainly increased, leading to a boom
in salmon farming. The rising popularity of this inexpensive, commonly
dined upon fish appears be taking a negative toll on wild salmon
populations.
Wild baby salmon, known as smolts, are
being infected with sea lice at rates almost 75 times higher than
normal while passing through commercial salmon farms on their way
to the ocean. Sea lice are parasites that eat away at
the skin, blood and flesh of salmon. Antibiotics are used to ward
off these pests, which infest salmon farm pens that can hold tens
of thousands of fish. Because smolts are at a vulnerable stage in
their development, being infected with sea lice can ultimately lead
to their premature death.
The Smolts' Migration Route
Researchers sampled the number of sea lice on the smolts every
mile or two along their 60-mile migration route to the ocean; along
their route, the wild baby salmon pass by large salmon farms. Large-scale
farms associated with the increased sea lice infections and declines
in adjacent wild populations are found in locations such as:
- Chile
- Norway
- Canada
- Scotland
Researchers noted that before reaching the salmon farms, there
was no sign of lice on the smolts, yet after passing through, the
fish were populated with the pests. Salmon farmers disagree with
such findings, claming they haven't seen any evidence of high
occurrences of sea lice around their farms that have led to complications
with wild salmon.
Regardless, a proposed solution to the lice problem is to shift
the salmon farms to closed systems in the ocean where the smolts
will be free from exposure to this deadly lice infection.
USA
Today March 31, 2005
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