arrival of subarctic zooplankton -- including
unusually high numbers of copepod species rarely
seen in Oregon -- is providing a smorgasbord for
offshore salmon and other species of fish,
according to researchers conducting a salmon
survey from Newport, Ore., to LaPush, Wash.
This is the 10th year researchers have conducted
the survey of juvenile salmon and preliminary
results suggest that numbers of both juvenile
coho and juvenile chinook surveyed this spring
were the highest they've recorded.
"We'll know more when we crunch the final
numbers, but it certainly looks like a banner
year for salmon survival -- primarily because of
a bountiful supply of the right kind of food,"
said Bill Peterson, a fisheries biologist with
NOAA who is based at Oregon State University's
Hatfield Marine Science Center in Newport.
The juvenile salmon surveys, conducted in
May, June and September, include the waters from
the central Oregon coast north to the tip of
Based on a long-term ocean observing program,
which Peterson initiated off Newport in 1996, it
has become clear that juvenile salmon respond
quickly to changing ocean conditions.
"When the ocean is in a cool phase, such as
existed from 1999 to 2002, juvenile salmon
survival was high and adult returns were very
high one year later for coho, and two years
later for chinook," said Peterson, a courtesy
professor in OSU's College of Oceanic and
Atmospheric Sciences. "After ocean conditions
suddenly changed in autumn 2002 to a warm phase,
salmon returns immediately began to decline."
The ocean off Oregon has begun to cool once
again, starting in July of 2006, after nearly
four years of warm ocean conditions, said
Cooler waters bring northern species of
copepods into the region to feast on
phytoplankton blooms triggered by summer
upwelling. Copepods are small crustaceans that
are major links in the food chain that supports
salmon, other fish, whales and seabirds.
Peterson's research suggests that northern
species -- which are lipid rich -- provide
better nutritional benefits for their consumers
than southern copepod species that are prevalent
during warm water regimes.
"This year, we've experienced one of the
earliest biological transitions to 'summer'
conditions in recent decades," Peterson said.
"The subarctic zooplankton not only arrived
extremely early, we are seeing unusually high
numbers of a group of copepod species rarely
seen off Oregon. These copepods are bigger than
our usual 'local' species, and pack on even more
"The transition began in March this year, the
earliest we've recorded during the 12 years of
observations made off Oregon," Peterson added.
"The two other years when the zooplankton
arrived anywhere near that early – in 1970 and
1972 – were characterized by very high salmon
Among the seldom seen copepod species
visiting Oregon this year are Neocalanus
plumchrus, flemingerii, and Neocalanus cristatus.
"Whether this means we're experiencing a
greater influx of subarctic water than usual, or
whether we're getting normal water transport
that happens to have a greater abundance of
copepods -- we don't know," Peterson said. "In
either case, it's good news for the fish that
feed on them, particularly some species of
groundfish and sablefish (black cod), which
"Of course," Peterson added, "we must see how
the ocean responds during the remainder of the
summer months before offering more firm