Why did several major herring, pilchard, and sardine fisheries collapse in the early 1970s?

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A worker in dark clothing inspects large frozen tuna lined up on the floor at Tsukiji fish market in Tokyo, Japan, using a tool to check the fish. — commercial fishing Worker in the Tsukiji fish market, Tokyo.

The collapse of several major pelagic fish stocks in the early 1970s, including the northeast Atlantic herring, South Atlantic pilchard, and West African sardine, is generally attributed to overfishing.

Following World War II, rapid advancements in fishing technology—such as the invention of the power block for purse seiners and the use of synthetic, rot-proof nets—led to a fourfold increase in the annual world fishing catch over 40 years. By the late 1960s, large fleets of purse seiners were supplying factory mother ships capable of processing massive quantities of fish daily. This intensive industrialization of commercial fishing eventually exceeded the sustainable limits of these marine resources, leading to the severe population declines observed by the early 1970s. These collapses prompted coastal states to seek greater control over their waters, eventually leading to the establishment of exclusive economic zones to protect remaining stocks.1