The California Department of Fish and Game has been casting nets in the Delta for the last couple of weeks. It is not so much about what they catch, as what they don't.
Since 1967, biologists have searched the murky waters of the Delta looking for what is left of the once thriving fish populations. They take detailed notes on everything, from what they catch, where they catch it, to the temperature of the water.
"We sample from San Pablo Bay up to the lower Sacramento River and through the San Joaquin," said Dave Contreas with the California Department of Fish and Game.
But again, the number of fish the department catches is extremely small.
"What we started noticing were downward trends particularly at the start of 2000, 2001," said Contreas.
It is a phenomenon known as pelagic organism decline -- a sudden and dramatic change in a population. In fact, several species continue to be at record lows.
"We've seen drastic abundance changes in Delta smelt -- end of the year striped bass, longfin smelt, and threadfin shad," said Contreas.
The longfin smelt numbers have been so low they could be put on the endangered species list.
But it is the Delta smelt that gets all the attention. It is only found in the Sacramento Delta. It is a tiny little fish with enormous importance. Scientists and environmentalists believe it is the best indicator of the Delta's overall health. It was listed as a threatened species in 1993 and is currently being considered as a candidate for the endangered species list.
"In the seventies, according to catch data, they used to catch hundreds of smelt in a spot, in one station. It's amazing what they used to catch," said Contreas.
No one really knows what is causing the decline, but scientists suspect everything from pollution, to pesticides, to invasive species, to the millions of gallons of water diverted to the Central Valley and Southern California.
Earlier this year, a judge ordered a nearly 30 percent reduction in the amount of water being released to Southern California to protect the Delta smelt.
In a worst case scenario, restrictions to protect both Delta smelt and longfin smelt in 2009 could amount to nearly a 50 percent slash in water deliveries from the state's primary water delivery systems.
Researchers are desperately trying to keep the Delta smelt from going extinct.
"On-site we have probably have, maybe about 50,000 fish," said Joan Lindberg, director of the UC Davis Fish Conservation and Culture Lab in Byron.
Lindberg suspects her lab may have nearly as many fish in captivity as are in the wild. Her goal is to preserve the genetic diversity of the species in case it does become extinct. They will soon begin rearing longfin smelt.
The smelt raised there are primarily for research, but may someday provide a back-up plan should the little fish disappear from the wild.
"There is a possibility if the population really looks like it's going to go extinct, that biologists will consider restocking some of these fish," said Lindberg.
But putting the fish into the water now will not necessarily increase the numbers. Lindberg says there will have to be significant improvement in the health of the Delta in order for that to happen.
According to the Department of Fish and Game, there is little sign of that happening. It will wrap up this season's count next month, but does not expect the numbers to change much. With each pull, there is less hope that the haul will show signs that the Delta smelt population is recovering.
"I think you might have to see 10 times as many fish coming in the hauls to say that it looks like it might be coming back," said Lindberg.
And by Lindberg's assessment, that is a very long way off.
"I think that humans have to work hard to repair some of the damages that they've caused in the past and that will take years and years I think."
Written and produced by Ken Miguel.