The State Water Resources Control Board endorsed a $1.2 million plan this week that would create a refuge for the endangered Delta smelt, the tiny fish that scientists say serves as an indicator of the estuary’s overall health.

The water board’s action is in response to the sharp decline in population of the smelt and other similar fish that are native to the Sacramento-San Joaquin Delta. The board’s staff reported at Tuesday’s meeting in Sacramento that the goal is to preserve the species in case the natural population dies out.

The water board, at its Tuesday meeting, pledged $600,000 to the California Department of Fish and Game, which operates the Fish Conservation and Culture Laboratory near Byron. The Department of Water Resources has also pledged $640,000.

The Department of Fish and Game will use the money to expand the lab, which is the home of about 1,000 wild-born smelt. Because the fish are on the brink of extinction and legal limits dictate how many of the smelt can be removed from their natural habitat, the state will not be allowed to catch any more fish to start a refuge.

The $1.2 million the state has put up for the refuge is expected to keep the project going through the end of 2008.