Several species of fish that indicate the health of the Delta environment are is sharp decline. Delta smelt populations have plummeted over the last three years and the species is in danger of extinction, according to some scientists. The young-of-the-year striped bass numbers have collapsed and the threadfin shad have disappeared.
On the positive side, salmon populations have increased substantially, while other species declined.
Despite extensive studies of the Delta ecosystem by CalFed, no one knows for sure why there has been such a sharp decline in key fish populations, particularly in the absence of drought and new schedules for pumping water from the Delta to the Central Valley and Southern California.
There are three suspected causes of the Delta's decline: invasive species, toxics (including pesticides) and the water pumps. If CalFed had concentrated on these specific possibilities instead of broader-based studies, perhaps we would have a better idea of what is harming the Delta and what could be done about it.
There are two leading theories now being studied that are interrelated. One theory is that invasive species, particularly the "overbite clam" from Asia is invading much of the Delta and is consuming zooplankton, which is a major food source for young fish.
The clams prefer brackish water that is saltier than much of the Delta, or at least saltier than the Delta used to be. Salinity levels in the Delta have increased during the fall for the past 10 years. Saltier water would allow the clams to spread and rob fish of their food.
A second theory is that pumping water in the fall and winter instead of the spring has backfired. Instead of protecting fish, it is killing them. The number of fish in pumps has increased dramatically during the winter.
The reason may be that the fish are escaping saltier water downstream and seeking zooplankton that the overbite clams have not diminished. There also is concern about a new kind of pesticide being used in the Central Valley called pyrethroids, which is used to protect land animals but are more toxic to fish.
Finally, scientists are focusing on specific potential causes of the Delta's ecosystem problems. It may still be several years before causes of the problems can be pinpointed and even more time before they can be resolved, if in fact there are solutions.
Meanwhile, the demand for water from agricultural and urban users is increasing while CalFed's revenues are being depleted. Yet there does not seem to be a sense of urgency in addressing the Delta's problems.
But that could change if the Delta's ecosystem continues to deteriorate and water pumping to Southern California is curtailed. That would create a crisis situation, which all too often seems to be the necessary catalyst for political action in California.