Several people in this thread are displaying attitudes that show exactly why much of our ecosystems are the way they are. It's overall a very human problem and I can't pretend that I don't do the same at times. People dismiss their individual acts as having no real effect on things, not taking into account the combined effect of what everyone else is doing.
Laws are (usually) there for a good reason. If you're not supposed to collect a certain fish, DON'T DO IT. Don't think, well I only collected one or two, that won't hurt anything. What if every person who visited that location "only collected one"? That could mean hundreds or thousands or more fish removed from the population. Laws on releasing fish should not be taken lightly either. It could only take ONE fish that has come in contact with an exotic disease to introduce it to a whole body of water or watershed and it might only take a couple fish to start off some new invasive population if released into a new area. There are plenty of examples out there of how little individual effort it takes to REALLY mess things up in our environment