Blaming a favorite scapegoat -- water agencies that supply our cities and farms -- while ignoring scientific evidence is irresponsible and won't bring back the salmon ("Where have the salmon gone?" Feb. 10, editorial).
Many insist that stopping delta water exports or releasing more water from reservoirs will restore Central Valley salmon. However, abundant evidence shows that neither is a primary cause of the salmon's decline. At least three other factors -- ocean conditions, commercial fishing and non-native predators -- contribute to the salmon's decline.
Biologists are reaching a consensus: Ocean conditions are the primary cause of recent declines in salmon numbers, especially in 2007.
If the decline in Central Valley chinook salmon were primarily related to water exports from the Sacramento-San Joaquin Delta or river flows, then only these salmon would decline. But chinook salmon stocks in Oregon, Washington and British Columbia are also down. And coho salmon have dropped by more than 70 percent in California and Oregon coastal streams since 2004. For the coho salmon, there are no export facilities (canals or aqueducts) and few dams to blame.
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Chinook salmon spend part of their lives in fresh water and part in the ocean. Their migrations expose them to natural and man-made threats. If conditions are unfavorable at any point, fewer fish return to spawn in fresh water.
Variable conditions off the Pacific Northwest coast over the past 30 years negatively impacted the chinook. From 1977-1998, these waters were unfavorably warm, resulting in a significant drop in returning salmon. Conditions were particularly variable during the past 10 years.
El Niño (warming) periods and La Niña (cooling) periods corresponded to significant declines and rebounds in salmon numbers.
In 2005, scientists observed catastrophic ocean conditions in the Pacific Northwest. Normally an upwelling brings nutrients from the ocean floor to the surface, providing critical support for the entire marine food chain. In 2005, this upwelling failed to appear for the first time in 50 years. Many species starved. Several scientific models predicted much lower salmon numbers in 2007 and possibly 2008. So far those forecasts have proved accurate.
When Klamath River chinook salmon declined after 2000, the ocean harvest of adult Central Valley salmon was expanded so commercial fishermen could make up economic losses. This past April, commercial salmon fishing was allowed off Fort Bragg for the first time in 20 years. The 2007 ocean harvest jumped 31 percent over the previous 10-year average and 218 percent over 2006. Commercial fishing likely contributed to the 2007 decline in salmon.
A century ago, humans introduced non-native striped bass into the delta. Bass eat young salmon. A 2003 study identified stripers as a serious threat to chinook salmon. Field studies conducted by the water agencies of the San Joaquin River Group Authority have confirmed this with conclusive evidence of young chinook, tagged with radio transmitters, consumed by striped bass in the delta.
Member water agencies have demonstrated long-term commitment to protecting salmon. We have extensively restored salmon habitat. For 10 years, our research has gathered data on how much water flow salmon need. We provide increased river flows each spring, carefully monitoring the effects. This aids the survival of young salmon migrating through the delta.
Water agencies are not to blame for ocean conditions, commercial fishing or non-native predators. Ignoring scientific evidence only jeopardizes salmon more. One day, blaming the favorite scapegoat may jeopardize the water supplies our city and farm customers depend on.
Short is coordinator of the San Joaquin River Group Authority. Member agencies are: Merced, Modesto, Oakdale, South San Joaquin and Turlock irrigation districts; the city and county of San Francisco; Friant Water Users Authority; and the San Joaquin River Exchange Contractors Water Authority.