Company officials say the mere cost of operating the plant, from soaring utility bills and rent to the cost of paying union wages to most of its workers, have reached the point where keeping the facility open is no longer viable. All 250 workers will be let go.

Compounding problems, says Chicken of the Sea president Dennis Mussell, is that there just aren't enough tuna left to catch in the waters off Southern California. Though the company will convert the hulking structure on Terminal Island's Cannery Street into a fish warehouse, all of the canning operations will be moved to American Samoa—where tuna and inexpensive labor both are plentiful.

At its post-war peak, LA County's tuna industry operated nearly two dozen canneries employing more than 17,000 Angelenos. But the business began to weaken in the 1970s, as more companies started moving to lower-cost areas such as American Samoa and Puerto Rico.