Fisheries Management and Maximum Sustainable Yield; Part 1

The history of the question of limits might be expressed in three dominant historical themes: 1) that, after consideration, the world appears limitless (“It must be that nature has made all things specifically for the sake of man,” said Aristotle), 2) that the world appears limited, prompting the question of “How much can we take?,” (Henry David Thoreau said, “A man is rich in proportion to the number of things he can afford to let alone”) and, 3), that we have harmed the world, shifting the question to, “How much must we leave?” (“For one species to mourn the loss of another is a new thing under the sun,” said Aldo Leopold).

Possibly the first official acknowledgment that fisheries could be exhausted came in 1631, from England’s King Charles I, who proclaimed, “And the former abundance of fish is turned into such scarcitie and deareness, that…especially our citie of London, and even our owne Court, are many times unprovided for their necessary dyet…therefore…the nets heretofore called traules…which is notoriously known to destroy the said frie & spawne…is… forbidden by the law.”

But not everyone got that memo. Fully two and a half centuries later, in 1883, the eminent scientist Thomas Huxley stated, “probably all the great sea fisheries, are inexhaustible; that is to say, that nothing we do seriously affects the number of the fish (read his whole speech here).

At the time of his speech, though, there was already plenty of evidence that major fisheries were in fact declining. The response to that evidence is called “fisheries management.”

Tuna Net, Southern Ocean © Paul Sutherland/National Geographic

First question: what do we mean by “fisheries management?” Sometimes, usually in freshwater, fisheries managers might raise and stock fish into public waters, introduce a non-native species so people can catch it, seek to improve spawning habitat, or augment wild populations using hatcheries. But usually, fisheries management is the effort to limit human activities—where, when, and how people can fish, and what they can take—in a fishery.

What’s a “fishery?” A fishery is basically an effort to catch fish. It is the collective effort of people trying to catch or gather specific wild aquatic organisms for commerce, recreation, or subsistence. That means that a fishery can be lots of things. Usually it’s defined by species, gear, fishing group, or region, depending on what’s under discussion. So we might speak, for instance, of “the salmon fishery,” or “the salmon purse-seine fishery,” or “the subsistence salmon fishery,” or “the Bristol Bay salmon fishery,” etc. It depends on how you define it, but it’s always some collective effort to catch ocean animals.

Underlying essentially all fisheries management is the recognition that human extraction can cause depletion, diminishing long-term benefits that people can get.

Fishermen haul in a bluefin tuna caught in the Mediterranean. © Brian Skerry/National Geographic

In the Western world, ocean fisheries management has usually focused on the question of, “How much can we take?” And it has usually approached that question with concepts such as maximum sustainable yield and, more recently, attempts to introduce different approaches that go by names such as adaptive management, Bayesian approaches, and ecosystem-based management.

Answers to, “How much can we take?” have usually come in the form of limits on amount of fish caught, their sizes, fishing gear, numbers of fishing permits, fishing times, and fishing areas. Some other cultures, particularly Pacific islanders, put almost all their emphasis on managing access to fishing areas.

Such place-based management has crossed to the West as attempts to designate some areas as reserves or “marine protected areas”—places closed to fishing, where human extraction of all or most organisms is prohibited. Marine protected areas are certainly looking like the approach that could be most widely applied around the world, with the most good. But the idea has a long way to go to gain acceptance and widespread implementation.

In Part 2 we’ll look at the concept of “maximum sustainable yield.

Blog author: Dr. Carl Safina