Throwing the Little Ones Back

Throwing the Little Ones Back: "

Throwing the little fish back, a common practice, causes fish to shrink over time since there is selection against the survival of larger fish:



Survival of the Smallest, Ecology, Scientific American: Any commercial fisher or weekend angler knows to “throw the little ones back.” The idea is to give small fish time to grow up... But that strategy may actually be harming fish stocks. Ongoing experiments on captive fish reveal that harvesting only the largest individuals can actually force a species to evolve undesirable characteristics that diminish an overfished stock’s ability to recover, says David O. Conover, director of the Marine Sciences Research Center at Stony Brook University. The results may explain why many of the world’s most depleted stocks do not rebound as quickly as expected.



The genetic effects appeared in Atlantic silversides, a small, usually fast growing fish. Conover brought a batch of wild silversides to his laboratory in 1998. He and his students then reared six generations, each time removing the largest 90 percent from one group, the smallest 90 percent from another group, and a random 90 percent from a third.

By 2002 it was plain to see that killing off the largest fish had a dramatic effect. Individuals in that group were only about 70 percent the average weight of their r"