California Bay-Delta Authority Advisor, chemist, Wim Kimmerer

Kimmerer is a researcher at the Romberg Tiburon Center, a research and teaching laboratory of San Francisco State University located in Marin County.

He has a background in chemistry and biological oceanography with interests in zooplankton ecology and the ecology of estuaries with an emphasis on the San Francisco Bay.

Experts agree there is no clear link between declining fish populations in the Delta and water exports.

Something is killing the delta smelt and there is a major effort underway to find out what.  However recent analyses by leading Delta fishery experts indicate that export pumps are probably not a major factor. 

Wim Kimmerer, research scientist with the Romberg Tiburon Center (San Francisco State University) and advisor to the California Bay-Delta Authority (CBDA), reported at the August 11, 2005 CBDA meeting that a number of fish species exhibit declining populations, including young striped bass, Delta smelt, shad and others.  According to Kimmerer, scientists have determined there is no clear statistical link between fish abundance and water exports – one of most frequently suspected causes.

Kimmerer told the panel the Delta represents a complex ecosystem and recent declines in some fish species defy simple explanations.  While some species like Delta smelt are declining, salmon populations are thriving, he said.  And he said there have been major improvements in the science used to manage the Delta.

Dr. BJ Miller, another expert on Delta fish, has reported similar findings based on his analysis of water exports, fish abundance and food sources.  Miller said his research has found no statistical correlation of any kind - either direct or indirect - between how much water is exported and the number of fish that survive to adulthood.  In some years when a lot of water is exported, smelt do fine.  In other years when exports are severely curtailed, smelt numbers plunge.

There is evidence of a strong correlation between Delta smelt abundance and the availability of the smelt's primary food source - zooplankton called Pseudodiaptomus, which was introduced into the Delta in 1986.  In years when there is a lot of Pseudodiaptomus in the same parts of the Delta where the Delta smelt congregate, a large number of the fish survive to adulthood.  When there is a shortage of the food source in the Delta, the numbers of Delta smelt drop sharply.

Legislators hear from expert panel
Members of the California State Assembly Committee on Water, Parks and Wildlife, during an August 18, 2005 hearing on the Delta Ecosystem Crisis, heard that there is "no connection between species decline and export pumping."  That statement was made by Steve Hall, executive director of the Association of California Water Agencies.  Hall stated that scientists have acknowledged that no connection exists.

Not an isolated problem
Similar problems have also been observed along the Pacific Coast, as noted in the San Francisco Chronicle.  Ocean plankton have largely disappeared from the waters off Northern California, Oregon and Washington, mystifying scientists, stressing fisheries and causing widespread seabird mortality. 

The plankton disappearance is caused by a slackening of what is known as "upwelling:" the seasonal movement of cold, nutrient-rich offshore water into areas near the shore.

While problems in the Delta appear to be heavily influenced by invasive species consuming the zooplankton, there is a distinct correlation between the abundance of food, on the low end of the food chain, such as zooplankton and phytoplankton, and the health of fish and bird populations.