SAN FRANCISCO (Map, News) - As the Cosco Busan powered out of the Bay on Thursday, tests revealed that it had left behind traces of spilled fuel in shoreline fish-breeding habitats.

The Hong Kong-based container ship spilled 58,000 gallons of heavy shipping fuel into the Bay on Nov. 7 after slamming into a tower of the Bay Bridge. The toxic slick spread from Drakes Bay south to San Mateo County, U.S. Coast Guard charts show.

On Thursday, California Department of Fish and Game biologist Ryan Watanabe and herring fisherman Dennis Deaver conducted a test to check for fuel on the Bay floor within 500 feet of the shoreline.

They cast an anchored, 390-foot herring gill net over popular fishing and fish-spawning habitat near Treasure Island, Angel Island and Tiburon.

Deaver, who has been fishing for 41 years, described the test results as “scary.” He said the department should cancel this winter’s commercial herring season.

“We may need all the fish to spawn to secure the future of the fishery,” Deaver said. He said buyers in Japan — San Francisco’s main herring market — will avoid the fish if any is oiled.

Department biologist John Mello, who oversees the Bay fishery, said the test results would be provided to federal and state agencies that managed post-spill cleanup efforts. They could decide to close the herring season, he said, which would normally have started this month.

Although no globs of oil clung to the net, as the pair had feared, nets picked up oil-covered pieces of eelgrass and flotsam, and the anchor and rope were covered with what appeared to be oily silt.

“We’ll have to send that to the lab to see if that mud had some oil in it,” Watanabe said. “It kind of looked like it did, but sometimes you get detrital mud — and it’s just black.”

Analysis of the vegetation, flotsam and silt samples is due to begin today, according to Watanabe.

When Deaver hosed down the net after six tests, a thin oil slick covered the water that pooled at the bottom of the boat.

Herring eggs laid on oiled rocks or vegetation won’t hatch, according to Deaver and Watanabe.

The Department of Fish and Game also sent scuba divers into deeper parts of the Bay on Wednesday and Thursday to conduct vegetation surveys.

The divers found less eelgrass in the Bay than last year, according to department biologist Ryan Bartling, but he said the reduction might not have been caused by the oil spill.

“We had a visibility of one-inch,” Bartling said Thursday. “What small amount [of eelgrass] we saw looked fairly healthy, with no noticeable oil.”

The death toll

The most recent information about the Cosco Busan cleanup efforts:

123 Total personnel employed

1,818 Birds dead on arrival

1,083 Total birds captured

648 Birds that died in facility

400 Birds released

45 Birds washed remaining in facility

1,300 Remaining feet of boom laid out

Source: Cosco Busan

Unified Command

jupton@examiner.com