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<i>Helpful to read the official summary...<br><br>
</i><b>NMFS Report on the Sacramento River Fall Chinook Salmon Decline -
2009<br>
</b>Report to the Pacific Fishery Management Council (PFMC)<br>
<a href="http://swr.nmfs.noaa.gov/media/SalmonDeclineReport.pdf" eudora="autourl">http://swr.nmfs.noaa.gov/media/SalmonDeclineReport.pdf</a><br>
<font size=5>Executive summary<br>
</font><x-tab> </x-tab>In
April 2008, in response to the sudden collapse of Sacramento River fall
Chinook salmon (SRFC) and the poor status of many west coast coho salmon
populations, the Pacific Fishery Management Council (PFMC) adopted the
most restrictive salmon fisheries in the history of the west coast of the
U.S. The regulations<font size=1> </font>included a complete closure of
commercial and recreational Chinook salmon fisheries south of Cape
Falcon, Oregon. Spawning escapement of SRFC in 2007 is estimated to have
been 88,000, well below the PFMC’s escapement conservation goal of
122,000-180,000 for the first time since the early 1990s. The situation
was even more dire in 2008, when 66,000 spawners are estimated to have
returned to natural areas and hatcheries. For the SRFC stock, which is an
aggregate of hatchery and natural production, many factors have been
suggested as potential causes of the poor escapements, including
freshwater withdrawals (including pumping of water from the
Sacramento-San Joaquin delta), unusual hatchery events, pollution,
elimination of net-pen acclimatization facilities coincident with one of
the two failed brood years, and large-scale bridge construction during
the smolt outmigration (CDFG, 2008). In this report we review possible
causes for the decline in SRFC for which reliable data were
available.<br>
<font size=1><x-tab> </x-tab></font>Our
investigation was guided by a conceptual model of the life history of
fall Chinook salmon in the wild and in the hatchery. Our approach was to
identify where and when in the life cycle abundance became anomalously
low, and where and when poor environmental conditions occurred due to
natural or human-induced causes. The likely cause of the SRFC collapse
lies at the intersection of an unusually large drop in abundance and poor
environmental conditions. Using this framework, all of the evidence that
we could find points to ocean conditions as being the proximate cause of
the poor performance of the 2004 and 2005 broods of SRFC.We recognize,
however, that the rapid and likely temporary deterioration in ocean
conditions is acting on top of a long-term, steady degradation of the
freshwater and estuarine environment.<br>
<font size=1><x-tab> </x-tab></font>The
evidence pointed to ocean conditions as the proximate cause because
conditions in freshwater were not unusual, and a measure of abundance at
the entrance to the estuary showed that, up until that point, these
broods were at or near normal levels of abundance. At some time and place
between this point and recruitment to the fishery at age two, unusually
large fractions of these broods perished. A broad<font size=1>
</font>body of evidence suggests that anomalous conditions in the coastal
ocean in 2005 and 2006 resulted in unusually poor survival of the 2004
and 2005 broods of SRFC.<font size=1> </font>Both broods entered the
ocean during periods of weak upwelling, warm sea surface<font size=1>
</font>temperatures, and low densities of prey items. Individuals from
the 2004 brood<font size=1> </font>sampled in the Gulf of the Farallones
were in poor physical condition, indicating<font size=1> </font>that
feeding conditions were poor in the spring of 2005 (unfortunately,
comparable data do not exist for the 2005 brood). Pelagic seabirds in
this region with diets similar to juvenile Chinook salmon also
experienced very poor reproduction in these<font size=1>
</font>years. In addition, the cessation of net-pen acclimatization in
the estuary in 2006<font size=1> </font>may have contributed to the
especially poor estuarine and marine survival of the 2005 brood.<br>
<font size=1><x-tab> </x-tab></font>Fishery
management also played a role in the low escapement of 2007.
The<font size=1> </font>PFMC (2007) forecast an escapement of 265,000
SRFC adults in 2007 based on<font size=1> </font>the escapement of 14,500
Central Valley Chinook salmon jacks in 2006. The realized escapement of
SRFC adults was 87,900. The large discrepancy between the<font size=1>
</font>forecast and realized abundance was due to a bias in the forecast
model that has since been corrected. Had the pre-season ocean abundance
forecast been more accurate and fishing opportunity further constrained
by management regulation, the<font size=1> </font>SRFC escapement goal
could have been met in 2007. Thus, fishery management,<font size=1>
</font>while not the cause of the 2004 brood weak year-class strength,
contributed to the<font size=1> </font>failure to achieve the SRFC
escapement goal in 2007.<font size=1> </font>The long-standing and
ongoing degradation of freshwater and estuarine habitats<font size=1>
</font>and the subsequent heavy reliance on hatchery production were also
likely contributors to the collapse of the stock. Degradation and
simplification of freshwater<font size=1> </font>and estuary habitats
over a century and a half of development have changed the<font size=1>
</font>Central Valley Chinook salmon complex from a highly diverse
collection of numerous wild populations to one dominated by fall Chinook
salmon from four large<font size=1> </font>hatcheries. Naturally-spawning
populations of fall Chinook salmon are now genetically homogeneous in the
Central Valley, and their population dynamics have<font size=1>
</font>been synchronous over the past few decades. In contrast, some
remnant populations<font size=1> </font>of late-fall, winter and spring
Chinook salmon have not been as strongly affected<font size=1> </font>by
recent changes in ocean conditions, illustrating that life-history
diversity can<font size=1> </font>buffer environmental variation. The
situation is analogous to managing a financial<font size=1>
</font>portfolio: a well-diversified portfolio will be buffeted less by
fluctuating market<font size=1> </font>conditions than one concentrated
on just a few stocks; the SRFC seems to be quite<font size=1>
</font>concentrated indeed.<br>
<font size=1><x-tab> </x-tab></font>Climate
variability plays an important role in the inter-annual variation in
abundance of Pacific salmon, including SRFC. We have observed a trend of
increasing<font size=1> </font>variability over the past several decades
in climate indices related to salmon survival. This is a coast-wide
pattern, but may be particularly important in California, where salmon
are near the southern end of their range. These more extreme
climate<font size=1> </font>fluctuations put additional strain on salmon
populations that are at low abundance<font size=1> </font>and have little
life-history or habitat diversity. If the trend of increasing
climate<font size=1> </font>variability continues, then we can expect to
see more extreme variation in the abundance of SRFC and salmon stocks
coast wide.<br>
<font size=1><x-tab> </x-tab></font>In
conclusion, the development of the Sacramento-San Joaquin watershed
has<font size=1> </font>greatly simplified and truncated the once-diverse
habitats that historically supported<font size=1> </font>a highly diverse
assemblage of populations. The life history diversity of this historical
assemblage would have buffered the overall abundance of Chinook salmon
in<font size=1> </font>the Central Valley under varying climate
conditions. We are now left with a fishery that is supported largely by
four hatcheries that produce mostly fall Chinook<font size=1>
</font>salmon. Because the survival of fall Chinook salmon hatchery
release groups is<font size=1> </font>highly correlated among nearby
hatcheries, and highly variable among years, we<font size=1> </font>can
expect to see more booms and busts in this fishery in the future in
response<font size=1> </font>to variation in the ocean environment.
Simply increasing the production of fall Chinook salmon from hatcheries
as they are currently operated may aggravate this<font size=1>
</font>situation by further concentrating production in time and space.
Rather, the key to<font size=1> </font>reducing variation in production
is increasing the diversity of SRFC.<font size=1> </font>There are few
direct actions available to the PFMC to improve this
situation,<font size=1> </font>but there are actions the PFMC can support
that would lead to increased diversity<font size=1> </font>of SRFC and
increased stability. Mid-term solutions include continued
advocacy<font size=1> </font>for more fish-friendly water management and
the examination of hatchery practices to improve the survival of hatchery
releases while reducing adverse interactions with natural fish. In the
longer-term, increased habitat quantity, quality, and<font size=1>
</font>diversity, and modified hatchery practices could allow life
history diversity to increase in SRFC. Increased diversity in SRFC life
histories should lead to increased<br>
stability and resilience in a dynamic, changing environment. Using an
ecosystem<font size=1> </font>based management and ecological risk
assessment framework to engage the many<font size=1> </font>agencies and
stakeholder groups with interests in the ecosystems supporting
SRFC<font size=1> </font>would aid implementation of these
solutions.<br><br>
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