- FREDERICTON (CP) -- Scientists have discovered what could be a major clue
to solving the mystery of the disappearing Atlantic salmon.
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- The same broad class of chemicals suspected
of causing gender bending in certain animals may also be fouling the salmon's
ability to change from freshwater to saltwater fish.
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- That would explain why seemingly healthy
young salmon leave their spawning rivers and then simply vanish at sea,
a mystery that has been attributed to everything from hungry seals to global
warming.
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- A new study by researchers with the federal
Department of Fisheries and Oceans and Environment Canada has found that
past spraying programs against the spruce budworm may have knocked off
more than the tree pest.
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- A fisheries scientist in New Brunswick
-- which sprayed heavily against the budworm for years -- said Tuesday
the study demonstrates a relationship between chemical use and salmon survival,
thereby introducing another factor in the battle to save the wild fish.
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- "Salmon have to change from a freshwater
to a saltwater fish and there's a whole process of development that could
be influenced by changes in hormones," said Wayne Fairchild.
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- "What if the chemical exposure did
something to influence juvenile salmon just as they were going out to sea?
When we did the study, to our surprise, all the data that we had between
forest spray exposures and salmon populations started lining up. On one
river, we saw a linear relationship, a straight line between how much was
sprayed and how many fish came back."
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- Fairchild was alerted to a possible connection
between gender-bending chemicals and dwindling salmon stocks when he heard
about the alarming discovery of male trout with feminine traits in British
rivers.
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- Gender-bending compounds, known as endocrine
disrupting chemicals, can alter hormones in animals and give males female
characteristics. One of the most famous gender-bending pollution cases
involves an area in Florida where male alligators have been discovered
with penises much smaller than normal.
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- Fairchild knew from previous studies
that the budworm spray program in Atlantic Canada, home to some of world's
most storied salmon rivers, included high concentrations of a compound
called nonylphenol, which mimics the female hormone estrogen.
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- Provinces such as New Brunswick, Newfoundland
and Nova Scotia sprayed against the budworm for years, using nonylphenol
in the pesticide mix from the mid-1970s to the mid-80s.
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- Fairchild said that even though there's
no longer a budworm spray program, hormone-disrupting chemicals are still
getting into the environment through sewage treatment and industrial effluent.
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- The widespread use of birth control pills
is spilling into the environment through sewage, he said.
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- "The current relevance is that the
concentrations we were looking at after forest spraying are not far from
concentrations you can see in industrial and municipal sewage treatement
effluents today," he said.
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- Fred Whoriskey, vice-president of research
with the Atlantic Salmon Federation in St. Andrews, N.B., said the chemicals
appear to disrupt the salmon's ability to move from fresh to salt water,
a transition critical to the salmon's life cycle.
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- "The hypothesis is that these endocrine
chemicals that are coming through are affecting those little salmon and
they're doing fine in fresh water but when they hit the ocean, they disappear."
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- But Whoriskey doubts hormone confusion
is the sole and final answer to the mystery of declining Atlantic salmon
populations.
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- "It can't be the only answer,"
he said. "There are very few places where we have the answer. It's
a combination of answers; it's cumulative impacts that are causing these
declines. We can't point to one smoking gun and say that's the only one."
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- Atlantic salmon numbers declined sharply
in most of Eastern Canada's 500 or so salmon rivers in 1997. The 1998 numbers
are still being tabulated.
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- The fish has been in trouble for years
due to habitat destruction and overfishing, but scientists have long believed
something else was happening at sea to further deplete stocks.
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