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Overfishing Simplified…Then Complexified

May 27, 2009

Overeating…overeager…overactive bladder—words that start with “over” rarely describe positive things. Overfishing is no exception.

The concept of overfishing is simple. It’s fishing, overdone. When we remove fish from a population at a faster rate than the population can reproduce, we’re overfishing. Some fish are easier to overfish than others. Late bloomers like orange roughy—which become sexually mature somewhere between 20 and 32 years of age and can live to be 130—make overfishing a cinch. Orange roughy became a dinner plate celebrity in the 1980s. Demand for the deep-sea fish skyrocketed so fishing pressure grew and grew and grew. But the fish couldn’t keep up with their growing popularity and the population tanked.  

Other fish, like Atlantic herring, are reproductive rockstars. These fish mature quickly, produce lots of offspring and die relatively young. As a result of what some would call a rather wanton lifestyle, Atlantic herring are less likely to be overfished. Sadly, even rockstars can be overfished with enough effort. Atlantic cod make lots of babies (quickly), but more than four centuries of hard-core fishing finally left their populations in shambles.

Obviously, overfishing is bad news for the overfished fish, but it also does a doozie on the entire ecosystem, turning a “situation normal” into one big SNAFU.

Take the Cape Gannets’ situation, for instance. Cape Gannets are big-ass seabirds that nest on islands off the coasts of Namibia and South Africa. (They’re related to boobies, FYI*.) Normally, the gannets and the pelicans that share their turf feast on the anchovies and sardines found in the surrounding super-productive coastal waters. Alas, the gannets and pelicans weren’t the only ones who knew about the abundance of anchovies and sardines in these waters. People fished and fished and fished until the stocks were overfished, bringing us to the current “AFU” conditions. Now, some Cape Gannets are flying up to 450 kilometers a day to get food and pelicans are eating Cape Gannet chicks. Truly AFU.

While returning from a 450 kilometer foraging trek only to discover that your neighbor ate your chick would truly suck, Cape Gannets aren’t the only species suffering from the side effects of overfishing. In fact, the overfishing of sharks has caused an ocean-wide SNAFU.

Sharks eat skates and rays, but with fewer sharks around, the populations of skates and rays are booming. While that’s good news for the skates and rays, it’s bad news for their food—and the rest of the ocean. Cownose rays eat bivalves like scallops and clams. Bivalves are the ocean’s filters so—thanks to the depletion of sharks that’s led to an overpopulation of rays who have eaten all the bivalves—the ocean’s water quality is suffering. And juvenile fish now have fewer places to hide since the cownose rays destroy seagrass beds in their search for bivalves.

Around Caribbean coral reefs, the absence of sharks has made room for a new king: the grouper. Groupers eat herbivorous fish who eat algae. Without a cleaning crew to keep it in check, algae thrive and outcompete coral. Without coral, there’s no coral reef and without a coral reef, there’s nowhere for little coral reef fish to hide. Again, truly AFU.

Still, there’s hope that we can return to situation normal by making the switch from overfished seafood to sustainable seafood. To find out which fish is which, check out these guides:

Seafood Watch regional guides

Seafood Watch iPhone App

Blue Ocean Institute Seafood Guide

Environmental Defense Fund’s Seafood Selector


*The “Y” in FYI refers to those of you who can’t help smiling whenever you read the word “booby.”

4 Comments leave one →
  1. December 1, 2009 3:16 pm

    The iPhone App for choosing seafood wisely is such a great idea! I will definitely be downloading that—just as soon as I get an iPhone. It’s better than the cards because what is and is not sustainable changes so often. Thanks for the info.


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