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Phase 1: The Sardine Capital of the World

In the 1930s and 1940s, Monterey on the coast of California was known as the Sardine Capital of the World. A single street, Cannery Row, was lined with more than 30 canneries and reduction plants. At its peak the industry employed three to four thousand people, close to half the town, and the boats landed hundreds of thousands of tonnes of Pacific sardines every year.

Within about ten years it was all gone. The sardines vanished, the canneries fell silent one by one, and the last one closed in 1973.

https://maps.app.goo.gl/h5oRtt6hEYWVkADk9

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Where this lesson is going

Monterey Bay holds two very different stories. One animal, the sea otter, was hunted almost to extinction and then recovered. One fish, the sardine, was caught in enormous numbers and then collapsed and never fully returned. By the end of this lesson you will be able to explain why the same bay produced two such different outcomes, and what that tells us about how we should set limits on fishing.

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Phase 2: The bay before the boats

A kelp forest and its keystone

You already studied the sea otter of the Pacific kelp forests as your example of a keystone species in ecology.1.5 Communities and ecosystems. It belongs in this lesson too, because the otter is the other half of the Monterey Bay story.

From memory first, then check below. Otters eat sea urchins, and urchins graze kelp, so where otters are present the kelp forest thrives, and where they are removed the urchins multiply and strip it to bare rock, leaving an urchin barren. That is a trophic cascade, and the otter is the keystone species holding it together.

The part that matters today is what happened to the otters. They were hunted for their fur until, by the early 1900s, only about 50 animals were left on the central California coast. Protected from hunting from 1911 and listed as threatened since 1977, they have slowly recovered around Monterey, and the kelp forests with them. Hold onto that, because the sardine story ends very differently.

Reconstruct the cascade

1. Put these three organisms in order to show the feeding relationship, using arrows to show the direction energy flows: kelp, sea otter, sea urchin.

2. In one sentence, predict what happens to the kelp forest if the otters are removed.

3. What single word describes a species like the sea otter, whose removal would change the entire ecosystem?

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Links to earlier lessons. You met keystone species in ecology.1.5 Communities and ecosystems and food webs and trophic cascades in ecology.2.3 Biomass and food webs. Giant kelp is one of the macrophytes from water.3.1 From plankton to plate.

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Phase 3: The fishery that collapsed

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4.3.5 Overexploitation has led to the collapse of fisheries.

Consider details of one fishery collapse: the dramatic and lasting decrease in stocks to a point where the commercial fish can no longer recover.

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What happened to the Monterey sardine

The Pacific sardine (Sardinops sagax) was once the largest fishery in the western hemisphere. Through the 1930s and 1940s the annual California catch reached around 700,000 tonnes, and the canneries of Monterey processed sardines on an industrial scale.

The fishery peaked around 1946. Over the next few years the catch crashed, from an average of roughly 234,000 tonnes to about 24,000 tonnes, a fall of about 90 per cent in five years. By the mid-1950s the Monterey fishery was effectively finished, and a complete ban on commercial fishing ran from 1967 to 1986.

What makes this case so useful is that overfishing was not the only cause. The Pacific sardine population rises and falls naturally over decades, linked to changes in ocean temperature. The collapse happened because the fleet kept fishing hard through one of these natural downturns. Taking too many fish during a natural decline turned a dip into a collapse, and the stock never returned to anything like its former size.

There is a postscript that matters for the next part of this lesson. The sardine recovered somewhat through the 1990s and Monterey briefly became a sardine port again. Then it collapsed a second time: the population fell by about 97 per cent after 2006, and regulators closed the fishery from 2015. Scientists argued that, just as in the 1950s, fishing had been allowed to continue too far into a known decline.

Build a collapse timeline

1. Use the text to complete the table. For each period, note what was happening to the fishery and what was driving it: fishing, natural change, or both.