The population of the tiny delta smelt has hit an all-time low in the vast estuary east of San Francisco Bay, according to new survey figures. The results trouble scientists who consider the fish an indicator of the health of the Sacramento-San Joaquin River Delta, the waterway that funnels water to two-thirds of Californians.
The population of a second bellwether species, longfin smelt, also was at a near-record low since measurements began in 1969. Two other harbinger fish species – threadfin shad and young striped bass – had increases in the most recent survey, but still are far below historic levels.
Scientists are concerned about the crash of the four fish species, and frustrated that they have been unable to determine the cause after a year of emergency research. Biologists had hoped to see a rebound in the populations this fall because water conditions have been good.
A new round of studies next year will be aimed at narrowing the suspects, with a focus on factors such as water pumping to Southern California; San Joaquin farmers; San Francisco Bay Area cities; invasive species, including a prolific clam that is eating the fish's food; and toxic chemicals.
Researchers from the state Department of Fish and Game calculate the fish populations based on an index after sampling fish with nets throughout the Sacramento-San Joaquin Delta from September through December.
This year's smelt index was just one-third of last year's survey result. Longfin smelt also declined sharply from last year, though the index is up from a record low set in 1992.
Mammoth mapping job
Researchers have announced they have mapped a portion of the genome of the extinct wooly mammoth.
Hendrik Poinar, a molecular evolutionary geneticist at McMaster University, extracted DNA from a well-preserved mammoth specimen found in the Siberian permafrost. He sent it to his colleagues at Penn State, who have sequenced 30 million base pairs, about 1 percent of the entire mammoth genome.
Poinar, who published his study in Science, said it will take a year to map the entire genome. Once it is mapped, Poinar said, "with this level of genetic data, we can begin to look at genes to determine what makes a mammoth a mammoth. We can finally understand the subtle differences between a mammoth and its closest living relative, the Indian elephant."
Compiled from news service reports.
