[env-trinity] OSU Ocean Conditions Report

[Byron Leydecker]

http://oregonstate.edu/dept/ncs/newsarch/2008/Dec08/oceanconditions.html


2008 Ocean Conditions for Fish Among Best in Half-Century


NEWPORT, Ore. Ocean conditions during 2008 for many fish species in the
Pacific Northwest, including chinook salmon, were greatly improved because
of a huge cold water influx that settled in across much of the northern
Pacific Ocean a phenomenon not seen on this scale in years.

In fact, scientists who surveyed near-shore waters from Newport, Ore., to
LaPush, Wash., this year found the highest numbers of juvenile chinook
salmon they've encountered in 11 years of sampling.

The reason may be traced to the Pacific Decadal Oscillation
<http://www.nwfsc.noaa.gov/research/divisions/fed/oeip/ca-pdo.cfm> , a
pattern of climate variability that historically has shifted between warm
(positive) and cool (negative) regimes over cycles of 20 to 30 years. During
2008, the PDO was the most negative it has been since 1955, according to
Bill Peterson, a NOAA fisheries biologist at Oregon State Universities
Hatfield Marine Science <http://hmsc.oregonstate.edu>  Center.

We usually see cold water conditions for a few months once upwelling begins
in late spring and early summer, said Peterson, who has a courtesy
appointment in OSUs College of <http://www.coas.oregonstate.edu>  Oceanic
and Atmospheric Sciences. Since April of 2007, though, we've been in a
constant summer-state ocean condition, which is something wave never seen in
more than 20 years of sampling. And were not sure why.

Strong, continual upwelling has fueled phytoplankton growth that forms the
basis of the marine food web. Cold water has drawn a huge biomass of
northern copepods from the Gulf of Alaska, and these zooplankton species
have high fat reserves that provide a rich diet for anchovies, herring and
other baitfish, which in turn become prey for salmon, ling cod and other
creatures.

The ocean
<http://www.nwfsc.noaa.gov/research/divisions/fed/oeip/a-ecinhome.cfm>  is
thick with these large copepods, which accumulate fat as a way to survive
the winter, Peterson said. When the Pacific Decadal Oscillation is in a
positive phase and warmer water moves into the coast from offshore and the
south, the copepods we see are species that are smaller and don't retain
lipids.

Peterson said anecdotal evidence from other researchers at OSUs Hatfield
Marine Science Center suggests that recruitment for juvenile ling cod and
other rockfish was extraordinary in 2008. Seabirds, including pelicans and a
large murre colony at Yaquina Head, were healthy and well-fed. And there was
a large population of sand lances a small baitfish that feeds on copepods.

If there is a downside, Peterson says, it is that the survey didn't find as
many juvenile coho salmon in 2008 as the scientists had hoped. The number of
juvenile chinook, on the other hand, was 2.4 times higher than any other
survey recorded in the past 13 years, Peterson said. The scientists used an
array of nets in their survey, including a trawling net as tall as a
five-story building and as wide as half a football field.

Though 2008 has been a banner year for ocean conditions and many fish
species it is too early to know what the future holds for ocean conditions
or fish runs. The Pacific Decadal Oscillation has been shifting more rapidly
between warm and cool phases, possibly in response to climate change. A
positive phase, characterized by warm, less-salty water, occurred from 1925
to 1947, followed by a negative phase of cooler, saltier water from 1948 to
1976. Then another positive phase took over and lasted through the powerful
El Nino of 1998.

Since then, however, the regimes have been much shorter. The PDO was
negative from 1999 to 2002, positive from 2003 to 2006, then abruptly
shifted to cooler waters during the last two years. Will this latest
cold-water regime last two years or two decades?

"That's the million dollar question", Peterson said.

Peterson and his colleagues have received a grant from NASA to track the
source of the cold water to see if it has circulated from the Gulf of Alaska
through an advection process, or is the result of a different upwelling
pattern, bringing deep water to the surface. However, sea surface
temperatures haven't dropped as much as temperatures lower in the water
column.

Temperatures recorded this year at a sampling station five miles west of
Newport, at a depth of 50 meters, were the coldest in the 13 years they've
been measured. This suggests to Peterson that the ocean is becoming more
stratified, which is consistent with climate change models. Those same
models also suggest more annual variability in ocean conditions.

The year 2005 was one of the worst in history, as delayed upwelling caused a
food shortage that led, among other things, to the collapse of the
Sacramento River chinook salmon run, Peterson said. In contrast, 2008 has
been one of the best years on record and though its a generality, cold water
usually means good things for salmon.

We just don't know how long this is going to last.

Byron Leydecker, JcT, Chair

Friends of Trinity River

PO Box 2327

Mill Valley, CA 94942-2327

415 383 4810 

415 519 4810 cell

bwl3 at comcast.net

bleydecker at stanfordalumni.org

www.fotr.org 

 

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