Cold Ocean Means More Salmon
Ocean temperatures off the Northwest Coast have remained
below normal and may stay that way for the rest of the year,
judging from the continued cooling of waters near the
equator, the Climate Impacts Group (CIG) from the University
of Washington reported last week.
That means La Niña conditions should stick around for
some time to come, boosting basic biological productivity in
nearby waters, good news for juvenile salmon who will be
heading for the ocean in a few months.
(An official La Niña episode is defined as any five-month
period when sea-surface temperatures in the middle of the
equatorial Pacific remain half a degree C below normal).
The last official La Niña occurred from September 2000 to
March 2001. Before that, a stronger La Niña took place
between June 1998 and June 2000, coming off a very powerful
El Niño that ended officially in March 1998.
By 1999, ocean conditions had improved drastically off
the Pacific Coast, with salmon populations increasing in
kind, with return rates for many salmon runs improving by an
order of magnitude or more.
Lately, coastal sea surface temperatures (SSTs) have been
at least 1 degree C below normal along the Washington coast,
and at least 2 degrees C below normal along the Oregon and
much of the California coast, according to the CIG's
"This pattern of colder than normal west coast SSTs is
consistent with the cold ENSO conditions that have dominated
the equatorial Pacific in the last several months," they
However, they also said the cooler conditions are slowly
heading toward a warmer state, according to the latest
numbers that make up the Pacific Decadal Index that tracks
long-term warming and cooling trends.
"The existing pattern of colder than normal SSTs along
the west coast of North America and on the equator, and
warmer than normal SSTs in the central north Pacific is
characteristic of the cold polarity of the PDO phenomenon.
The amplitude of this pattern in September, October,
November, and December was -0.36, -1.45, -1.08, and -0.58,
respectively, indicating that the PDO has diminished in
strength since October."
But the La Niña that has appeared seems to be stronger
than some scientists had anticipated, "with mean
October-November-December SSTs 1.48 degree C below the
1971-2000 normal in the Niño 3.4 region (5N-5S, 170-120W),
the coldest SSTs at this time of the year since 1988 and the
6th coldest in the 58 year record."
These conditions may stick around for awhile. The NOAA
Earth System Research Laboratory experimental SST forecast
calls for the PDO pattern to remain negative for the rest of
Nearby ocean temperatures began cooling again in 2006
after two hot years in a row. Canadian researchers measuring
SSTs off Vancouver Island found that 2004 and 2005 summer
water temperatures were "two of the four warmest in almost
50 years of sampling along this line." But since mid-August
of 2006, SSTs have been below normal.
The changes should benefit salmon stocks up and down the
West Coast, where it was reported last week that 2007 fall
chinook returns (natural and hatchery) to the Sacramento
River were near an all-time low. Only 90,000 returned, when
the objective was 122,000 to 180,000 fish. About 317,000
natural and hatchery chinook reached the Sacramento in 2006.
The 2007 Sacramento return was the lowest since 1973, and
jack counts were only about 10 percent of average, which
likely means another extremely poor run for this year.
Some critics blame water diversions in the river for the
poor return, but ocean conditions were poor when the fish
went to sea in 2005. A lack of tiny shrimp in the waters off
San Francisco led to a huge die-off among seabirds in 2005
Fishermens' groups are already talking about getting
another relief package from the federal government similar
to $64 million in aid that helped out many commercial
fishermen and related businesses in California and Oregon
after drastic harvest cuts were implemented in 2006 to help
the weak chinook run on the Klamath.
But these days the Klamath seems to be doing just fine.
About 50,000 wild fall chinook returned to spawn there last
fall, twice the number from the previous year, and better
than any of the three years before that.
Up the coast, Columbia River fall chinook numbers were
down considerably last year from the recent past as well,
with fall chinook counts at Bonneville Dam at less than half
the 10-year average. Poor ocean conditions in 2004 and 2005
were likely responsible for the downturn.
Jack counts for Bonneville tules took a 40-percent jump
in 2007, which should signal a much-improved fall run. Jack
counts for the upriver bright run are also better, which has
managers expecting an above-average run back to the famous
Spring runs in the Columbia are expected to make a huge
bounce back from improved ocean conditions, as well. This
year's spring chinook run above Bonneville could be way up
there--possibly the third highest since 1938, when the dam
was completed. In December, Columbia Basin harvest managers
released their preliminary number--269,000 springers above
Bonneville--three times the size of the 2007 run.
More potentially positive news: one NMFS researcher told
NW Fishletter that it's not uncommon for another La
Niña to follow a year behind the first one.
The following links were mentioned in this story:
The Pacific Northwest Climate CIGnal