How Fishing Screws With Ecosystems

Fight disinformation: Sign up for the free Mother Jones Daily newsletter and follow the news that matters.


800px-Pieni_2_0139.jpg Fishing provokes volatile fluctuations in the targeted populations, though no one really knows why or how. Until now. Researchers from Scripps Institution of Oceanography have found that current methods of fishing decapitate the “age pyramid:” lopping off the few large, older fish who make up the top of the pyramid and leaving a broad base of faster growing small fish. This rapidly growing base is unstable, a finding with profound implications for fisheries management. The reason being that even though fishing typically extracts the larger members, fishing regulations often impose minimum size limits to protect the younger fishes.

For example: Imagine a container of water with one 500-pound fish. With food, it grows a little bigger. Without food it gets a bit smaller. Imagine the same container with 500 one-pound fish. They eat, reproduce and the resulting thousands of fish boom, quickly outstripping the resources and the population crashes. These many smaller fish—with the same initial biomass as the larger fish—can’t average out the environmental fluctuations, and in fact amplify them through higher turnover rates that promote boom and bust cycles.

“The type of regulation which we see in many sport fisheries is exactly wrong,” said George Sugihara of Scripps. “It’s not the young ones that should be thrown back, but the larger, older fish that should be spared. Not only do the older fish provide stability and capacitance to the population, they provide more and better quality offspring.” These more valuable (to the ecosystem) older fish are what some researchers have called the BOFFFs: the big old fat female fish.

The danger is that current policies manage according to current biomass targets, ignoring fish size. The resulting population instability could, in theory, propagate systemically to the whole ecosystem—a domino effect eventually affecting fishermen too. This is especially true when trying to rebuild fish stocks. Which is the case with Atlantic swordfish. Industry pressures to resume fishing are based on the restoration of historic biomass levels, even though the swordfish are clearly undersized. The study results are published in the journal Nature.

Julia Whitty is Mother Jones’ environmental correspondent, lecturer, and 2008 winner of the Kiriyama Prize and the John Burroughs Medal Award. You can read from her new book, The Fragile Edge, and other writings, here.

DONALD TRUMP & DEMOCRACY

Mother Jones was founded to do journalism differently. We stand for justice and democracy. We reject false equivalence. We go after stories others don’t. We’re a nonprofit newsroom, because the kind of truth-telling investigations we do doesn’t happen under corporate ownership.

And we need your support like never before, to fight back against the existential threats American democracy faces. Fundraising for nonprofit media is always a challenge, and we need all hands on deck right now. We have no cushion; we leave it all on the field.

It’s reader support that enables Mother Jones to report the facts that are too difficult, expensive, or inconvenient for other news outlets to uncover. Please help with a donation today if you can—even a few bucks will make a real difference. A monthly gift would be incredible.

payment methods

DONALD TRUMP & DEMOCRACY

Mother Jones was founded to do journalism differently. We stand for justice and democracy. We reject false equivalence. We go after stories others don’t. We’re a nonprofit newsroom, because the kind of truth-telling investigations we do doesn’t happen under corporate ownership.

And we need your support like never before, to fight back against the existential threats American democracy faces. Fundraising for nonprofit media is always a challenge, and we need all hands on deck right now. We have no cushion; we leave it all on the field.

It’s reader support that enables Mother Jones to report the facts that are too difficult, expensive, or inconvenient for other news outlets to uncover. Please help with a donation today if you can—even a few bucks will make a real difference. A monthly gift would be incredible.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate