I was born in a crabbing town in Alaska and grew up in Anchorage.  I knew a lot of guys who were commercial fishermen.  There are a lot of different forms of fishing and all of it is pretty darn dangerous.  It seemed that every fisherman that I knew or met had scars or missing digits from their work.  They made a hell of a lot of money, but there were no guarantees.  Sometimes they made next to nothing.  
Some of the biggest money is in fish spotting though.  When a very short season opens, time is everything and boats hire fish spotters in planes to go looking for their fish.  The spotters typically get a portion of the boat’s earnings (like maybe 10%) and can have contracts with several boats.  Most of us could fly over a million dollars worth of fish and not have a clue what we are looking at; it’s a very specialized skill.  Good spotters are rare and can earn $100,000 on the first day of a season.