CORPUS CHRISTI, Texas (AP) _ Oystermen dealt a setback by an influx of toxic red tide last year predicted ruin as another outbreak led officials to extend a ban on shellfish harvesting today to two more Gulf bays.

The indefinite ban went into effect in Aransas Bay and adjacent St. Charles Bay on orders Friday from Dr. Robert Bernstein, state health commissioner.

Most of Texas' coast has been closed to shellfish harvesting since September because of an earlier bloom of the reddish microorganisms that kill fish. Humans who eat tainted shellfish can experience irritations to the eyes, throat and respiratory system.

''If it comes back, man, we're dead over here,'' said fisherman Benny Arispe, who works Aransas Bay and lives in nearby Fulton with his wife and four children.

''We're just going to have to go on food stamps or something, because that's how I make my living,'' he said. He said his truck was repossessed last week because of a poor shrimping last season and the previous red tide.

Red tide was detected in the Gulf near Galveston in August. Concentrations of flourishing organisms spread steadily south into coastal bays and beyond the Mexican border. The outbreak killed an estimated 22.2 million fish.

Officials have not yet determined whether the current red tide is a resurgence of that attack or a new patch from offshore.

Experts had expected the colder weather to kill the organism, but the tide may have been able to survive the mild south Texas winter that cooled bay waters to only 61 degrees.

This week's outbreak is ''nothing to get concerned about, and certainly not a problem for the Chamber of Commerce,'' said Kirk Wiles of the Texas Department of Health in Corpus Christi.

Wiles said the only immediate threat to public health would be from eating oysters, mussels and clams from the affected areas. Fish, shrimp and crabs are safe, he said.

The latest red tide extends across Corpus Christi Bay through Redfish Bay and into the Lydia Ann Channel between Port Aransas and Aransas Bay, an area about 25 miles wide, the Health Department said.

The fish-killing microscopic organism was found Thursday in Corpus Christi Bay near Marina del Sol and Cole Park, a department official said.

''It was a complete surprise to us,'' said Richard Thompson, director of the department's division of shellfish sanitation control in Austin. ''We certainly didn't expect it to bloom again this winter.''

Wiles said the Health Department sampled bay waters Thursday after a report of a kill of about two dozen fish in Corpus Christi Bay. Thompson said dead fish were also reported along the Corpus Christi shoreline.

Today's ban comes three days before a halt ordered by the Parks and Wildlife Department to oyster harvesting in all but San Antonio Bay. The ban, which begins Tuesday and runs until Feb. 20, was ordered to protect Gulf waters from over-harvesting.