[3] Ocean Is Number One Suspect In Sacramento Fish Declines
A pre-publication report released by NOAA Fisheries last week laid the blame for the Sacramento chinook decline at the feet of Mother Nature.
The federal scientists said most clues pointed to poor marine survival in 2005 and 2006 after the fish reached salt water as the main factor in the extremely poor adult returns for the past two years.
Only 88,000 natural and hatchery fall chinook returned in 2007 and 66,000 in 2008, while annual escapement goals are in the 122,000- to 180,000-fish range.
As late as 2004, California sport and commercial fishers were hauling in more than half a million fall chinook south of Point Arena, with another 300,000 fish left over to escape to Central Valley rivers.
But conditions changed quickly. Coastal upwelling was poor the following two years, which played havoc with offshore food webs. And fish weren't the only victims--thousands of seabirds starved as well.
Unfortunately, fish managers didn't see it coming, and allowed too many chinook to be caught in 2007, even though that harvest was only about one-third of what managers had expected.
The fishery should have been closed in 2007, as it was last year, when Congress provided $170 million to commercial trollers and related businesses to make up for the extended vacation.
The report looked at more than 40 different possibilities for the sudden decline, including increasing water withdrawals from the Sacramento system for agriculture.
However, it pointed out that though water diversions in January 2005 set records, they were at near-average levels in the spring when most of the juvenile fall chinook migrated to sea. In summer and fall, the Delta diversions rose again to near-record levels.
Pumping station in the Sacramento River Delta.
--courtesy California Dept. of Water Resources
In 2006, the report said, total water exports at state and federal pumping facilities in the south delta were near average for winter and spring, but were above average in June, and near records again that summer and fall.
The report also noted that gates were closed at the Delta Cross Channel from February through May, an action that has been in place since 1995.
"The evidence pointed to ocean conditions as the proximate cause," said the report, "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."
With both broods entering the ocean when upwelling was weak, sea surface temperatures warm and prey density low, it was no surprise that fish sampled off San Francisco in 2005 were "in poor physical condition," the report said.
NOAA scientists also noted that the harvest model used to regulate fisheries had overestimated pre-season abundance of the fall chinook in 2007.
"Had the pre-season ocean abundance forecast been more accurate and fishing opportunity further constrained by management regulation, the SRFC [Sacramento River Fall Chinook] escapement could have been met in 2007," the report said.
The feds said degradation of freshwater habitat and heavy reliance on hatchery fish--which has been up to 90 percent--likely played roles in the collapse as well.
And if the trend in climate variability continues, "more extreme" variation in the abundance of both Sacramento stocks and coast-wide salmon populations will be seen.
"We can expect to see more booms and busts in this fishery in the future in response to variation in the ocean environment," the report said.
The feds recommended operating hatcheries differently in order to both increase diversity and reduce adverse impacts on wild fish--which could help spread the risk to stocks in years of poor ocean conditions. They noted that some salmon that had left earlier and later than the fall chinook showed better survival.
The feds also called for better water management and more habitat restoration. They said a more diverse population would have developed a natural buffer to climate variations.
Instead, said the report, "We are now left with a fishery that is supported largely by four hatcheries that produce mostly fall chinook salmon."
But the situation has already improved. Ocean conditions have turned around and the Sacramento runs are expected to improve next year. -B. R.
The following links were mentioned in this story:
Report on Sacramento River Fall Chinook Stock Collapse
Subscriptions and Feedback
Subscribe to the Fishletter notification e-mail list.
Send e-mail comments to the editor.
THE ARCHIVE :: Previous NW Fishletter issues and supporting documents.
NW Fishletter is produced by Energy NewsData.
Publisher: Cyrus Noë, Editor: Bill Rudolph
Phone: (206) 285-4848 Fax: (206) 281-8035
