An analysis of potential
causes of an unprecedented collapse of salmon stocks returning
to the Sacramento River and elsewhere remains a work in
progress though some suspected causes have been eliminated.
Members of the scientific team carrying out the analysis
presented a progress report Monday at the Pacific Fisheries
Management Council's weeklong meeting in Boise.
The anticipated return was so small that the PFMC in April
set the most restrictive salmon fisheries in the history of
the West Coast. They cited the Sacramento collapse and
Sacramento River fall chinook and the exceptionally poor
status of coho salmon from Oregon and Washington and adopted a
complete closure of commercial and sport chinook fisheries off
California and most of Oregon.
"The sudden collapse of the Sacramento River fall Chinook
salmon stock is particularly curious in that it has been a
sudden and precipitous decline, with the most recent two brood
returns of two-year-old fish at consecutive new record low
levels and the most recent return an order of magnitude less
than the previous one," PFMC Executive Director Don McIsaac
said in April 4 letter to the NOAA Fisheries Service.
The letter asked that NOAA's fisheries science centers to
assemble a scientific workgroup to investigate a list of 46
potential causative factors and report its findings during the
The task is well under way but the task is too complex to
complete in such a short timeframe, according to John
Ferguson, head of the Fish Ecology Division at NOAA's
Northwest Fisheries Science Center in Seattle and a member of
the work group. The NWFSC's John Stein instead delivered a
progress report Monday. Stein is workgroup lead along with
Churchill Grimes of the Southwest Fisheries Science Center.
The work group's target is to produce a draft final report
in time for the PFMC's April 4-9 meeting in Millbrae, Calif. A
public comment meeting in California in January will allow the
opportunity for constituent input and comment.
"We still haven't found any big smoking guns" thus far,
Ferguson said Wednesday of potential calamities that might
have befallen the fish such as disease, oil spills or
abnormally high predation or human harvest as bycatch in other
fisheries or droughts and floods.
The progress report did note analysis of some of the
potential factors listed that are not likely explanations for
the sudden collapse of the Sacramento River fall chinook
salmon, and will be eliminated from further examination. The
list of potential contributors to the decline was whittled to
The working group met July 29-30 to review the list to
determine which potential factors identified could be
eliminated from further consideration. The initial decision to
eliminate an item was based on a consensus recommendation and
expert knowledge of the working group members.
The group met again Aug. 29 in Sacramento and conducted a
public meeting similar to those conducted by NOAA Fisheries in
its biological review or technical recovery team meetings
during which data and input on the issue from interested
individuals and agencies is sought. Participants were asked to
bring data on subjects pertinent to assessing the possible
causes for the decline, such as water withdrawals (Bureau of
Reclamation and California Department of Water Resources);
hatchery operations, e.g., production and release sites (U.S.
Fish and Wildlife Service/California Department of Fish and
Game); other pertinent events such as the Benicia bridge
construction (permit issuing agencies), according to the
The panel includes federal, state and tribal scientists, as
well as academics. It includes the PFMC's Chuck Tracy.
"We're still heavily leaning on a life cycle approach" to
the analysis, Ferguson said. Potentially numerous factors in
fresh water and saltwater may have caused the population
The expert scientific working group is to consider
potential causes of the recent collapse, "and what may be a
broader depression of salmon productivity for stocks involved
in west coast fisheries from the Sacramento River north to
Puget Sound. The working group will also assess whether the
performance of current stock predictors can be improved by
incorporating ocean environmental information," according to
the progress report.
"The approach on questions of broader salmon productivity
depression will be to address the issue from the perspective
of identifying and characterizing carrying
capacity/productivity degradation by suites of anthropogenic
impacts, climate effects or other effects that may have made
salmon populations less productive and less resilient to poor
environmental conditions," the document says.
"While ocean conditions may have been a proximate cause in
recent years, current populations are vulnerable to
precipitous decline from any number of factors. Thus,
restoring the productivity of various stocks, to the extent
feasible, will require a comprehensive approach to address
many potential issues."
"We're still very aware that ocean conditions were very
poor in 2005, and little better in 2006," Ferguson said.
That's when the juvenile fish that produce the 2007 and 2008
adult returns entered the ocean.