SACRAMENTO -- It's not much longer than your pinkie, an aquatic weakling that skulks in a single brackish backwater of the West.
Yet the diminutive fish is a big player in California water politics.
For years, the delta smelt's survival has been a bone of contention between water managers and environmentalists -- a subject of lengthy court cases and, of late, defining judicial decrees.
A decision Aug. 31 by U.S. District Judge Oliver W. Wanger requiring tougher protections for the tiny fish pushed the state's water managers toward uncharted territory in how they manage aqueduct exports out of the Sacramento-San Joaquin Delta, a key source of water for much of Southern California.
State water authorities warned that the ruling could cut exports from the delta by a third or more and possibly usher in widespread rationing of the sort hitting Long Beach.
The smelt is seen by biologists as the key indicator of the overall health of the Sacramento-San Joaquin Delta. Populations of several other fish in the delta are sagging, but the delta smelt tend to get attention from the federal bench and the media.
It's a small fish for such a big spotlight.
Delta smelt grow to only about 3 inches long and live about a year. Listed as threatened under the federal Endangered Species Act since 1993, they are off-limits to collectors and commercial harvest -- although it's unlikely anyone would jump at the chance to eat them. Out of water, the smelt is known to have an odor similar to that of cucumbers.
Biologists and environmentalists contend that the increasing diversion of delta water is nudging the fish toward extinction.
A recent survey showed the number of juvenile smelt to be less than one-tenth of normal -- an ominous sign for the species' survival.
In the years since it landed on the endangered list, the tiny fish has bedeviled state and federal water managers.
Known as being notoriously poor swimmers, smelt can fall prey to the powerful pumps that send delta water rippling down the California Aqueduct toward Southern California.
On occasion, water managers have shut down the pumps to ensure survival of the imperiled species.
The last shutdown was in June, when the pumps were stopped for nine consecutive days after unusually large numbers of smelt were being sucked up and killed.
But when authorities fired up the pumps anew, smelt fatalities once again soared.
With a fresh federal court decision, the possibility of rationing and water managers in a tizzy, the delta smelt may change the way water is moved up and down the Golden State.