Good point Orbert, altough you happen to be conveniently forgetting the entirety of the
Lotka-Volterra model/equations, which neatly explains the relationship between predators (and their population) and their prey (and their population).
Basically, if a predator finds low amounts of prey, they will reproduce less offspring (what with beeing to busy to get preggers and all), and the amount of predators in a certain area, will go down as well, untill it reaches a certain point at which the predation-pressure on the prey-population is low enough to allow it to recover back to its pre-bad-times place. A short delay after this, the population of the predators will also rise again, and the whole cycle starts over again.
Problem ofcourse with humans, is that our population has been on the rise for the last, oh, i dunno, millenium?
Aaaanyway, you can return back to the fishies now >.>
p.s. This is what you get for having a dutchie on the forum who had to study this at school. I actually bet im not the only one... Ohwell