[env-trinity] NOAA research links sea temp to Salmon return numbers

[Sari Sommarstrom]

THE COLUMBIA BASIN BULLETIN:
Weekly Fish and Wildlife News
www.cbbulletin.com.
March 7, 2008
Issue No. 430

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* NOAA RESEARCH LINKING SEA TEMPERATURE SWINGS TO SALMON RETURN NUMBERS

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.

That 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 ENSO.

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 estuary.

"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 to follow.

"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) mid-range.

"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 surveys."

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 surveys).

"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 Push, Wash.

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 
statistics.

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 returns.

"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:
http://www.nwfsc.noaa.gov/research/divisions/fed/oeip/a-ecinhome.cfm

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* NOAA SCIENTISTS STUDYING IMPACTS OF ANOMALY IN CALIFORNIA CURRENT IN 2005

NOAA scientists are reviewing unusual environmental conditions in the 
Pacific Ocean as the likely culprit for the dramatically low returns of 
chinook and coho salmon to rivers and streams along the West Coast of the 
United States in 2007.

Researchers from NOAA's Northwest and Southwest Fisheries Science Centers 
are comparing data on the low food production of the California Current in 
2005 that occurred when this year's and 2007's returning salmon would have 
been entering the ocean from their natal streams to feed and grow.

The cold waters of the California Current flow southward from the northern 
Pacific along the West Coast and are associated with upwelling, an ocean 
condition caused by winds that bring nutrients to the ocean's surface and 
is the main source of nourishment for the ocean's food web.

In 2005 a southward shift in the jet stream, delayed favorable winds and 
upwelling for the California Current, which normally begins in spring. The 
winds instead arrived in mid-July, causing high surface water temperatures 
and very low nutrient production within the nearshore marine ecosystem.

"We are not dismissing other potential causes for this year's low salmon 
returns," said Usha Varanasi, NOAA Fisheries Service Science Center 
director for the Northwest Region. "But the widespread pattern of low 
returns along the West Coast for two species of salmon indicates an 
environmental anomaly occurred in the California Current in 2005."

Data released Thursday by the Pacific Fisheries Management Council indicate 
the 2007 returns of fall chinook salmon to the Sacramento River in 
California's Central Valley were approximately 33 percent of what fishery 
biologists expected. Projections for 2008 are substantially lower than last 
year's estimate.

Coho salmon returning to spawning streams in California and Oregon are also 
considerably lower than predicted. A preliminary analysis found an average 
27 percent of the parental stock returning in 12 streams monitored in 
California. Even though coho returns appear to improve along the coast from 
south to north, Oregon Coast coho salmon had less than 30 percent of their 
parental stock return.

Coho salmon are listed as either endangered or threatened under the 
Endangered Species Act in the Central/Northern California and Southern 
Oregon watersheds
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