Sunday, May 28, 2006

Survival of the Itty-Bittest

Atlantic silversides
Seen on NPR's site, the story of how factory fishing is unintentionally selecting for smallness: Ocean Fishing May Spread 'Runt' Genes. It's obvious when you think about it: when the super-efficient factory fishing boats pick up all the biggest and best fish, year after year, only the smaller ones remain to procreate.
To see if catching all the big ones really could really make that happen -- force evolution to favor little fish -- Conover built his ocean eight years ago, and then started fishing.

Armed with long-handled nets, his team of researchers plays the role of the fishing boats. They scoop up silversides and then carefully measure each one, shouting out the length to a record keeper as they work.

Then, they throw back some of the fish. These are the lucky ones that get to pass along their genes.

Conover has now fished his way through eight generations of silversides.

He's found that, as predicted, if you take the big fish out of a school and leave the little ones, you'll end up with a population of runts. Moreover, it can happen very fast -- in just four years, or four generations.

Conover says those results suggest that fish out in the ocean can undergo the same kind of rapid evolution seen all the time on land.

"We know that pests evolve rapidly in response to pesticides," he says. "We know that diseases can quickly evolve responses to the antibiotics that we develop. All we're saying with fisheries is that the same process happens here. So we are undermining the capacity of the population to rebound from fishing."


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