With all of our midwestern talk about sustainably raised land animals, thinking about the fishing industry can often draw a big fat blank. Perhaps the answer is to just eat fewer fish, don't eat those fish which are endangered, look for sustainably caught fish or possibly assume that the ocean is so vast that we could never really deplete it.
Take one look into Four Fish by Paul Greenberg and the issue becomes much more complicated and fascinating. It is one thing to think about trying to control how a herd of cows or a flock of chickens is managed. Consider the vast seas, international borders, politicians, scientists and of course, global demand. Its complicated.