The U.S. Fish and Wildlife Service rules aim to protect the fingerling smelt when the fish migrate deeper into the Delta in winter to spawn, and then remain in the region as juveniles to feed. This natural migration makes the fish vulnerable to the massive state and federal water export pumps near Tracy, which reverse natural river flows and suck millions of fish to their deaths every year.
The Delta smelt population has declined steeply since 2000 and may be near extinction. Water agencies say the pumping limits have aggravated California's three-year drought, causing crop fallowing and economic woe in the San Joaquin Valley.
The rules are intended to restore the species and prevent the need for additional restrictions in the future.
