Canadian "fish cop" watches a fishing boat. Courtesy Fisheries and Oceans Canada.
summer's end, this kelp forest is lush and bursting with life. Kelp forests,
like the ones along the California coast, are major fish nurseries.
Doh, it's overfishing
So far, we've been focusing on the amount of fish eligible to enter our gullets. But let's not forget that fish have their own impact on the ocean. In fact, according to a recent study, overharvesting of fish, shellfish and other marine creatures has caused extreme, long-term ecological damage.
Using data from sediments, archaeological sites, historical documents and scientific literature, Jeremy Jackson of the University of California at San Diego, and colleagues wrote that "Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change" (see "Historical Overfishing..." in the bibliography).
That's strong language for a scientist. The examples came from major coastal ecosystems:
The relationship can be complicated, however. Sudden declines in species may reflect the loss of distant refuges, for example, or the addition of exotic species that affect key ecological relationships.
urchins eat giant kelp. In sufficient numbers, they can graze -- even
raze -- entire forests. Where urchins abound, new giant kelp have difficulty
surviving and growing.
The overfishing story also reflects how top predators maintain the structure and function of ecosystems -- on land and under the sea, Magnuson adds. "Fishing tends to remove the top predators [think swordfish and tuna] and release the control they exert on the rest of the food web."
By looking further into the past, Magnuson says, "The Jackson study ... was a major step forward. If we are complacent, we may have the feeling that the way it is now is the way it's always been."
Dip into our overfishing bibliography.
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