Delta smelt have hovered close to extinction for years, but biologists say they’ve never seen anything like this spring.

“There’s nothing between them and extinction, as far as I can tell,” said Peter Moyle, a U.C. Davis biologist who has studied smelt and other Sacramento-San Joaquin Delta fish species for nearly four decades. Last week, the state Department of Fish and Wildlife released the results of spring trawling surveys that track adult delta smelt. The surveys found just handfuls of fish across the huge area where they are known to spawn.