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 September meeting.

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 25.

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 progress report.

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 plunge.

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.