Labels For Transferring Life

Why do we not use 'hunting' when it comes to fish? Or crabs? Is the difference between 'catching' and 'hunting' simply motive? Or is it the result--life or death? Are insects hunted or caught? What is the real difference between 'gathering,' 'picking,' and 'harvesting'?--What do we get from the use of  these different terms to describe the point-of-no-return in ending life in order to then absorb it and continue our own?