Please answer a question about the following article about San Diego:

From the start of the 20th century through the 1970s, the American tuna fishing fleet and tuna canning industry were based in San Diego, "the tuna capital of the world". San Diego's first tuna cannery was founded in 1911, and by the mid-1930s the canneries employed more than 1,000 people. A large fishing fleet supported the canneries, mostly staffed by immigrant fishermen from Japan, and later from the Portuguese Azores and Italy whose influence is still felt in neighborhoods like Little Italy and Point Loma. Due to rising costs and foreign competition, the last of the canneries closed in the early 1980s.

Why were the canneries ultimately closed by the early 1980s?
rising costs and foreign competition