Collapse In California Delta Forage Species Alarms Fishery Scientists
Fish Sniffer Magazine -
By Dan Bacher
At first review, fish populations in California's Central Valley appear to be on the road to recovery.
The estimated ocean abundance of Sacramento River fall chinook salmon this year is the highest ever recorded – nearly 1.7 million. Spring run and winter run salmon populations, although still a fraction of historical levels, are on a definite upswing.
The adult striped bass population, after plummeting because of years of water exports, grew from 600,000 to over 1.5 million fish between 1996 and 2001, according to the California Department of Fish and Game (DFG).
And the white sturgeon population was estimated at 147,000 in 1997, while the current population is estimated at 80,000 with a present annual legal harvest rate of 5 percent, said Patrick Coulston, supervising biologist for DFG's Bay-Delta Branch. The population is regarded as “stable” by the DFG and is a far cry from the early 1900’s when the fish nearly become extinct in the Bay-delta estuary.
Yet amidst the positive signs among Central Valley gamefish species, the ecosystem of the Sacramento-San Joaquin Delta, the West Coast's largest estuary. appears to be in unprecedented trouble. “The Delta’s open water fish populations are mysteriously collapsing in a crisis that threatens the food web of the West Coast’s largest estuary,” stated Mike Taugher in his in-depth article, "Environmental Sirens in the Delta are Screaming,” in the Contra Costa Times on May 1.
Taugher’s story, featuring interviews with state and federal fishery biologists, makes the following alarming contentions:
• “Delta smelt, already a threatened species, fell last fall to the lowest level ever measured,” said Taugher.
• The juvenile striped bass population has also fallen to the lowest level recorded, according to the annual DFG surveys.
• “The key food source for small fish in the Delta, tiny organisms called copepods, are plummeting as well with numbers of a key species falling to extremely low levels,” he stated.
The article continues, “The rapid multiple declines could trigger measures that might affect water quality and supply from Contra Costa County to Southern California. Scientists say information in a number of different surveys of the Delta and Suisun Marsh revealed an ongoing, sweeping population crash that could not be explained by drought or any other easily identifiable cause.”
Randall Baxter, DFG Bay-Delta Program biologist, in a phone interview with me, confirmed the bad news about the Delta’s open water forage species, although he was not yet willing to describe it as a “population crash” before more research is done on the decline and its causes. The dramatic decline in open water species started about 3 years ago.
“The Delta smelt, threadfin shad, longfin smelt and juvenile striped bass numbers have dropped from low levels to even lower levels now,” he noted. “The populations have further diminished even though the water conditions have improved slightly.”
He is perplexed that adult striped bass numbers remain relatively strong, according to DFG tagging studies, while the numbers documented in the annual juvenile surveys continue to plummet.
Nonetheless, he emphasized, “the copepods that sustain the food chain have declined to the lowest levels ever. Something really serious is going on in the Delta. We’re in the process of developing studies to narrow down the cause of these declines that we will implement in June.”
Baxter also explained that the DFG surveys haven’t studied the bottom (benthic) organisms and have concentrated on the large river channels and islands. “We haven’t looked at other areas like Discovery Bay or the Sacramento Deep Water Channel,” he said.
Their surveys documenting the decline in threadfin shad have been backed by reports of sharp drops in fishing success among commercial threadfin shad fishermen. “The commercial guys are having to work much harder and longer to get bait for the shops,” he concluded.
There are three main factors that the DFG and federal government believe may be responsible for the alarming declines.
First, toxic chemicals, including pesticides and herbicides, may be having a big impact upon these forage species.
Second, introduced species, such as the Asian clam and feria densa (an aquatic plant), are believed to be impacting the food chain. Interestingly enough, the mitten crab population, after a population explosion in the late 1990’s, has declined to much smaller numbers now.
Third, continuing exports of Delta water have changed the Delta hydrology and are providing poorer habitat for these open water fish and invertebrates. Notably, the Delta pumps at Byron and Tracy exported water to the Westside Water District and Southern California at the second and third highest rates ever over the past two years!
Fisherman’s groups and environmental organizations quickly reacted to the news of the declines by blasting the state and federal governments for ramming through plans for more exports at a time when the Delta forage species are in such bad shape.
“The truly estuarine species such as striped bass are being most impacted by the decline of the Delta food chain,” said John Beuttler, consultant for the California Sportfishing Protection Alliance. “Yet the federal and state governments have abandoned striped bass restoration in favor of ESA-listed species like the winter run and spring run chinooks.”
In contrast, king salmon and steelhead spend a relatively short time in the Delta as they move down from the rivers to feed in the ocean.
Beuttler faults the CALFED Program - a joint agency of the state and federal governments - for meeting its goals of shoring up levees and providing “reliable water sources” for farms and cities, but failing to accomplish its fish restoration goals. Under the Bush administration, the program’s focus changed from trying to restore the ecosystem to developing more water storage facilities, including the proposed raising of Shasta Dam, building another dam on the San Joaquin River and constructing so-called South Delta “improvements.”
“We have consistently pointed out in CALFED and agency forums that export rates must be reduced, not increased, if the system’s food web is to be restored to a healthy productive capacity,” said Beuttler. “We said that more than a decade ago – and we’ve repeated it incessantly – that exporting some 60 percent of the estuary’s water and food web to points south has, beyond it’s annual deleterious impacts, cumulative affects which appear to be driving this declining ecological productively to the brink."
At the same time that biologists are documenting the decline of the Delta food chain, the CALFÉD leadership has made it known that the stalled South Delta Improvement Project is back on track with a draft environmental impact report due out in June. The project will increase diversion rates from 6,300 cfs to 8,500 cfs. “If that goes through, increasing diversion rates to 10,000 cfs and over looms over the ecosystem,” warned Beuttler.
“The theme of CALFED was ‘let’s get better together’,” said Beuttler. “However, under the current administrations in Washington and Sacramento, the only guys that are getting better together are the water contractors. Since we apparently can’t get better together, let’s at least figure how to remove the steam roller off our fisheries!”
House Democrats also reacted strongly to news of the decline. On May 12, Members of Congress from California and Arizona, led by Congressman George Miller (D-Martinez), called on state and federal agencies to explain their actions in the face of "drastic declines" in fish populations of the San Francisco Bay and Delta region.
With the alarming decline of forage species in the Delta being documented by scientists now, it is crucial that the federal and state governments immediately suspend all attempts to increase water exports. Unless the problems of the Delta are dealt with immediately, we can expect to see the gamefish recoveries of recent years flushed down the California Aqueduct and Delta-Mendota Canal.