North Pacific sea
surface temperatures have historically swung up and down in 20
to 30-year cycles, changing with it climatic and ecological
variables that shift the fate of salmon.
cold-warm-cold-warm pattern has quickened over the past 10
years -- exhibiting turnarounds that have lasted only four
years, according to research being conducted by the NOAA
Fisheries Service's Northwest Fisheries Science Center.
The good news is that this sea surface cycle, dubbed the
Pacific Decadal Oscillation, last year appeared to have
entered a negative, cool phase, which most often signals a
rise in the number of salmon that return to the Columbia River
basin in succeeding years.
The PDO, like shorter term La Nina/El Nino (ENSO) patterns,
is characterized by changes in sea surface temperature, sea
level pressure, and wind patterns. Past research has shown
that warm eras have seen enhanced coastal ocean biological
productivity in Alaska and inhibited productivity off the west
coast of the contiguous United States. Cold periods reverse
that north-south pattern of marine ecosystem productivity.
"The biology reacts quickly" to such changes in ocean
conditions, according to Edmundo Casillas, NWFSC Ocean and
Estuary program leader. "Salmon respond equally as fast."
During a Thursday presentation to the Columbia Basin's
Regional Forum Implementation Team, Casillas pointed out that
at no time since 1900 had there been a deviation from an
established PDO regime of longer than 16 months. Once
established, warm or cool regimes have stayed locked in with
an occasional brief lapse, sometimes influenced by a contrary
Most recent history shows, however, that the North Pacific
has had two shifts of four years duration recently: a cold era
from 1999-2002 and warm period from 2003-2006. Chinook salmon
returns to the Columbia mirrored those trends with total
numbers climbing upwards from 2000-2003, then declining for
the next four years.
The University of Washington scientist Nathan Mantua and
colleagues were the first to show that adult salmon catches in
the Northeast Pacific were correlated with the PDO.
Regardless of the duration of any ocean condition, it is
important that freshwater fish managers know what is happening
so they can evaluate the benefits of salmon recovery actions
and respond accordingly, Casillas said. Advancing global
warming could complicate things, affecting the duration and
variability of the large scale climate forces.
"You need to be cognizant of what's going on in the ocean
to do what you need to do in freshwater," Casillas said. In
anticipation of poor ocean conditions, as an example, hatchery
managers might scale back their production to reduce potential
competition between hatchery and wild fish for resources that
will be in short supply.
The NWRFC has for the past 10 years been monitoring a
variety of physical and biological ocean conditions that may
affect the growth and survival of juvenile salmon in the
northern California current off Oregon and Washington. The
30-40 mile swath of ocean represents the young fishes' first
saltwater experience after they leave the Columbia River
"That's when they're smallest and most vulnerable" to
predators and other natural forces, and when the recruitment
into future adult returns can most be affected, Casillas said.
Those physical, biological and ecosystem "indicators" have
for the past few years been fed into a forecasting tool that
documents current ocean conditions and potential impact on
salmon survival 1 to 2 years ahead of their actual return. The
NWFSC monitoring and forecasting focuses on that first year at
sea through food-chain processes.
The most recent forecast, released late last month, says
that the PDO tide has turned, shifting last year to a neutral,
and then a negative, cool phase. Environmental changes seemed
"What we're seeing is the ocean is improving," said
Casillas. The latest "Ocean Ecosystem Indicators of Salmon
Marine Survival in the Northern California Current" forecast's
indicators, cumulatively, fall in the positive (for fish)
"Most indicators in 2007 pointed toward greatly improved
ocean conditions compared to the previous few years.
Indicators that point to good salmon survival included a cold
ocean in winter/spring 2007, an early spring transition date,
high biomass of cold--water lipid--rich copepods, and a long
upwelling season." according to the updated NWFSC adult spring
chinook and coho forecast. "Negative indicators included weak
upwelling in late spring and summer, very warm sea surface
temperatures, and low catches of juvenile coho in September
Fish sampling last year also showed a good news-bad news
result. In June 2007, trawl surveys collected the third
highest number of juvenile spring chinook in the 10 years of
sampling. That suggests "improved adult spring chinook runs
can be expected in 2009," according to the forecast, when the
first adults from that year class return to the Columbia.
Catches of juvenile coho in September produced some of the
lowest catches of juvenile coho (7th worse in 10 years of
"Since it is widely believed that juvenile coho live only
within the upper few meters of the water column, we
hypothesize that the anomalously warm waters, in some way, led
to the demise of the juvenile coho.
"They either moved (out of the sampling area) or they died.
We think they died," Casillas said. The trawl surveys follow
eight transect lines running from Newport, Ore., north to La
The forecast calls for a poor coho return, though improved
numbers for coho that went to sea in 2007 and return in 2008.
The relatively early transition of the zooplankton community
in spring, and the high biomass of coldwater zooplankton
species could counter to some extent coho trawl catch
Ocean conditions at the time of the spring chinook's ocean
entry were "very good" last year.
"Since spring chinook juveniles reside in waters off Oregon
and Washington for only a few weeks before migrating north to
unknown waters, their survival might have been relatively well
supported by these conditions. These fish could begin to
return as early as spring 2009," the forecast says.
Adult return data displayed as part of the forecast show
that the 4-year period of cold ocean conditions (1999-2002)
resulted in good returns of chinook salmon. Warm ocean
conditions from 2003 to 2006 correspond with declining
"We expect at least one more year of poor returns from this
period, after which returns should begin to increase, so long
as the cold ocean conditions observed in 2007 continue into
2008 and beyond," the forecast says.
The forecast charts an "improving set of conditions" that
began later in 2006, Casillas said. The numerous variables
monitored came out, on average overall, in the mid-range for
fish that emerged from the Columbia in 2006, thus anticipated
an improved spring chinook return this year.
Federal, state and tribal fishery officials have forecast a
strong upriver spring chinook return this year. That
prediction was based in large part on a near-record return of
"jacks," fish that returned after only one year in the ocean.
The forecast can be found at: