JayVay

Darwin’s Fishing Net: Manipulating Complex Ecosystems

by Guest Blogger,
Tyler Kokjohn, Ph.D.

Darwins net2In an effort to protect fisheries, laws and treaties require trawlers to use nets with a mesh big enough to allow smaller, presumably young fish, to escape.  The basic idea is simple; capture and eat the big fish, but let the young ones live to reproduce and replenish the stock.  That is logical, but the evidence suggests that practice is not only failing, but in combination with overfishing it is doing something perverse; fish are growing more slowly, reaching sexual maturity earlier and, due to smaller sizes, producing fewer eggs (1).

Picture Darwin’s fishing net capturing the big ones, but always letting the little fish escape.  Using it over and over again, perhaps to a point of overfishing, is a powerful un-natural selection which leaves a fish population with proportionately more small fish.  Some escapees may be young…

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