With an ocean salmon fishing season set to open on April 2nd and fishery managers estimating that coastal waters currently boast more salmon than they have in five dismal years, it appears that the severe drop in salmon abundance in recent seasons has reversed.
But a program that tags young salmon and recaptures them as adults has produced data suggesting that Central Valley fish hatcheries, not environmental improvement, have spurred the Chinook salmon’s recovery. Many hatchery salmon are even trucked downstream for direct deposit into San Pablo Bay, and some experts believe that without this elaborate life-support system Sacramento River salmon might all but vanish.
Biologists with the Department of Fish and Game and the Fish and Wildlife Service found that tagged salmon, or smolts, born in hatcheries and left to travel unassisted downstream, through the Delta, and out to sea are several times less likely to appear as adults in catch surveys than juvenile salmon loaded into tanks and transported to release sites near the Carquinez Straits. Experts suspect the unassisted salmon are dying in the Delta, where water pumping facilities create hazards for small fish, either killing them directly or drawing them into sloughs and backwaters, where predators may wait. Information collected by the National Marine Fisheries Service has shown that as many as 92 percent of young salmon that travel unassisted from stream to sea may die in the Delta.
“Getting the fish around the Delta is critical,” said Roger Thomas, captain of the Salty Lady, a party fishing boat in Sausalito, and a board member of the Golden Gate Salmon Association. “Until we improve the health of the (river’s) ecosystem, we’ll have to keep trucking the fish.”
The discouraging data on salmon smolt survival comes from a joint effort by state and federal fishery managers to tag a portion of the 30 million fish they produce annually in Central Valley hatcheries and observe their rates of survival into adulthood. To make the young fish identifiable as adults, the fleshy dorsal lobe called the adipose fin is clipped from 25 percent of smolts prior to release. The same fish are fitted with nearly-microscopic “coded wire tags,” printed with numeric data. In 2010, 121 of these fin-clipped salmon — caught as adults — were reported by sport fishermen on boats out of Sausalito. Fish and Game biologists who removed and analyzed the coded wire tags from the 121 fish found that 81, or 66 percent, had been given a ride around the Delta and released into San Pablo Bay.
Coded wire tags turned over by commercial ocean fishermen that same summer showed that fish born in 2008 at the Coleman National Fish Hatchery on the Sacramento River and trucked to San Pablo Bay were seven times more likely to reach adulthood than their hatchery-mates released in the river. Wild salmon must also navigate their way to sea unassisted and presumably face the same threats in the Delta region.
But an assembly of West Coast salmon experts pro-posed in a March, 2011 report that the recent salmon collapse was due to a food shortage in the ocean, not hazardous conditions in the Delta. Two panels of government biologists appointed by the Pacific Fishery Management Council, or P-Council, wrote that spring winds, which drive the essential upwelling of nutrient-packed waters from the deep seafloor, failed to occur in 2005 and 2006, likely causing reduced abundance of phytoplankton and krill. This, in turn, seemed to cause a breeding failure in Cassin’s auklets at the Farallon Islands and likely caused starvation of young salmon, the report states.
However, strong winds and upwelling resumed in the spring of 2007. While the birds rebounded, salmon did not. This makes activists like John McManus, media director with Earthjustice in Oakland, skeptical of the report’s conclusion.
“How is it that poor ocean conditions caused the col-lapse of Delta smelt and longfin smelt (which live year-round in freshwater)?” McManus said.
Even a coauthor of the report — Chuck Tracy, a P-Council salmon staff officer — believes excessive water diversions might have played a major role in the collapse of the fall-run salmon population, which hit rock bottom in the fall of 2009, when 39,000 spawning adults returned to the Sacramento River — down from 800,000 in 2002. In an interview with the East Bay Express, Tracy said that high Delta pumping levels in the spring of 2007 combined with half or less the rainfall of normal years created “a ratio of pumping to water in the river that was much higher than usual.”
In 2005 and 2006, budget constraints disabled the trucking-and-Bay-release program, which has historically released about 50 percent of Central Valley hatchery fish in San Pablo Bay. Adult salmon populations crashed in the following years. The program has since resumed in force, and salmon numbers seem to be climbing. Biologists estimate that 1.1 million adult fish are currently holding off the California coast — about three times the estimated ocean population of last spring.
Melodie Palmer-Zwahlen, a biologist with Fish and Game’s Ocean Salmon Project, is currently analyzing data from the coded wire tags collected last summer by Bay Area ocean sport fishermen. She remains undecided on what is driving the rise and fall of salmon numbers.
“Is something happening to these salmon in the river,” she says, “or is something happening at sea?”
Dick Pool, president of the Concord-based fish conservation group Water4Fish, feels certain that the key problems dwell in the Delta.
“The ocean conditions did zap a lot of the fish in 2005 and 2006, but since then we’ve had excellent ocean conditions, but the fall run collapsed into a disaster zone,” said Pool. He believes the Delta environment remains as devastated as ever and that the current abundance of salmon could easily crash again. “Without that trucking program, we might have no ocean fishery.”
This article first appeared in the East Bay Express