Fish Evolve To Match Fishermen

Fishermen prefer to catch big fishes and fishing regulations tend to prohibit the harvest of the smallest individuals of a species. In response, fishes have evolved the ability to reproduce at a smaller size and/or younger age. If they can breed before they get big enough to be harvested their genes stand a much higher chance of being passed on. American plaice, Atlantic cod, Atlantic herring, Atlantic salmon, brook trout and chinook salmon all have appeared to grow more slowly and/or to reproduce at smaller sizes where and when they are heavily fished. Once, a large cod could eat a small boy. Now, a small boy could almost eat an entire cod.

~ Rob Dunn Scientific American