Both South Bay ports posted cargo gains again last month as the economy continued what appeared to be a slow march toward recovery.

The Port of Los Angeles experienced the largest gain, processing 660,517 container units – a 15.2 percent increase from the same period last year. A spokesman described it as the second-best January in the port’s history, surpassed only by January, 2007, during which 691,000 units were handled.

“It was encouraging to see 2011 start out so strongly,” said Phillip Sanfield, a port spokesman.

The Port of Long Beach, meanwhile, moved 474,960 container units, a 10.8 percent increase from the same month last year.

Art Wong, a spokesman for the port, said the high numbers came despite the departure one shipping company – California United Terminals – in December.

On the other hand, both spokesmen said, the numbers could have been inflated by the Chinese New Year which shuts down many factories in that Asian country for the first two weeks of February. “What we may be seeing,” Sanfield said, “was a push to ship cargo before the holiday slowed things down in February.”